The coronavirus disease (COVID-19) pandemic has increased pressure to develop low-cost, compact, user-friendly, and ubiquitous virus sensors for monitoring infection outbreaks in communities and preventing economic damage resulting from city lockdowns. As proof of concept, we developed a wearable paper-based virus sensor based on a molecular imprinting technique, using a conductive polyaniline (PANI) polymer to detect the lentivirus as a test sample. This sensor detected the lentivirus with a 4181 TU/mL detection limit in liquid and 0.33% to 2.90% detection efficiency in aerosols at distances ranging from 30 cm to 60 cm. For fabrication, a mixture of a PANI monomer solution and virus were polymerized together to form a conductive PANI sensing element on a polyethylene terephthalate (PET) paper substrate. The sensing element exhibited formation of virus recognition sites after the removal of the virus via ultrasound sonication. A dry measurement technique was established that showed aerosol virus detection by the molecularly imprinted sensors within 1.5 h of virus spraying. This was based on the mechanism via which dispensing virus droplets on the PANI sensing element induced hybridization of the virus and molecularly imprinted virus recognition templates in PANI, influencing the conductivity of the PANI film upon drying. Interestingly, the paper-based virus sensor was easily integrated with a wearable face mask for the detection of viruses in aerosols. Since the paper sensor with molecular imprinting of virus recognition sites showed excellent stability in dry conditions for long periods of time, unlike biological reagents, this wearable biosensor will offer an alternative approach to monitoring virus infections in communities.

Purpose:

The study aimed to (1) examine the feasibility of providing a training course on auricular point acupressure (APA) for clinical oncology nurses to integrate APA into real-world nursing care settings, and (2) examine the effectiveness of APA on cancer-related pain (CRP) under usual inpatient oncology ward conditions.

Methods:

This was a 2-phase feasibility study. Phase 1, an in-person, 8 hour training program was provided to oncology nurses. Phase 2, a prospective and feasibility study was conducted to evaluate the integration of APA into nursing care activities to manage CRP. Oncology patients were included if their pain was rated at ≥4 on a 0 to 10 numeric rating scale in the past 24 hours. Patients received 1 APA treatment administered by the nurses and were instructed to stimulate the points for 3 days. Study outcomes (pain intensity, fatigue, and sleep disturbance), pain medication use, and APA practice were measured by a phone survey daily.

Results:

Ten oncology nurses received APA training in phase 1. APA had been added to the hospital’s electronic health records (EHRs) as a pain treatment. In phase 2, 33 oncology patients received APA treatment with a 100% adherence rate (pressing the seeds 3 times per day, 3 minutes per time based on the suggestion). The side effects of APA were minimal (~8%-12% felt tenderness on the ear). After 3 days of APA, patients reported 38% pain relief, 39% less fatigue, and 45% improvement in sleep disturbance; 24% reduced any type of pain medication use and 19% reduced opioid use (10 mg opioids using milligram morphine equivalent). The major barrier to integrating APA into routine nursing practice was time management (how to include APA in a daily workflow).

Conclusion:

It is feasible to provide 8-hour training to oncology nurses for mastering APA skill and then integrating APA into their daily nursing care for patients with CRP. Based on the promising findings (decreased pain, improved fatigue and sleep disturbance, and less opioid use), the next step is to conduct a randomized clinical trial with a larger sample to confirm the efficacy of APA for oncology nurses to treat CRP in real-world practice. ClinicalTrial.gov identifier number: NCT04040140.

Abstract

We have developed a microscale hydraulic soft gripper and demonstrated the handling of an insect without damage. This gripper is built on Polydimethylsiloxane (PDMS) with the soft material casting technique to form three finger-like columns, which are placed on a circular membrane. The fingers have a length of 1.5 mm and a diameter of 300 µm each; the distance between the two fingers is 600 µm of center-to-center distance. A membrane as a 150 µm soft film is built on top of a cylindrical hollow space. Applying pressure to the interior space can bend the membrane. Bending the membrane causes the motion of opening/closing of the gripper, and as a result, the three fingers can grip an object or release it. The PDMS was characterized, and the experimental results were used later in Abaqus software to simulate the gripping motion. The range of deformation of the gripper was investigated by simulation and experiment. The result of the simulation agrees with the experiments. The maximum 543 µN force was measured for this microfluidic-compatible microgripper and it could lift a ball that weighs 168.4 mg and has a 0.5 mm diameter. Using this microgripper, an ant was manipulated successfully without any damage. Results showed fabricated device has great a potential as micro/bio manipulator.

Abstract

Osteo-enhanced human mesenchymal stem cells (OEhMSCs) secrete an osteogenic cell matrix (OCM) that mimics the composition of anabolic bone tissue and strongly enhances OEhMSC retention and subsequent bone repair in vivo. Here we demonstrate a system for rapid production of gelatin methacrylate microcarriers coated with decellularized OCM (OCM-GelMA) to serve as an injectable bone graft material with high osteogenic potential comparable to a clinically utilized gold standard, bone morphogenic protein 2 (BMP-2). OEhMSCs seeded onto OCM-GelMA secreted high levels of osteogenic and angiogenic cytokines and expressed higher levels of BMP-2 relative to OEhMSCs on bare GelMA microcarriers. OEhMSCs co-administered with OCM-GelMA microcarriers resulted in enhanced healing of murine critical-sized calvarial defects, which was comparable to that achieved with a BMP-2-laden gelatin sponge control. When tested in a murine femoral defect model, OCM-GelMA co-administered with OEhMSCs also induced profound bone growth within the defect. We submit that OCM-GelMA promotes OEhMSC paracrine release to accelerate bone repair, indicating their potential as a bone graft for use in minimally invasive surgery.

A low-cost and enzyme-free glucose paper sensor is presented as a promising alternative to glucose test strips. This paper-based glucose sensor is prepared with molecularly imprinted (MIP) polyaniline (PANI) electrode. The determination of glucose concentrations was studied by the impedance change of the paper sensor before and after the blood samples dispensing at a low frequency. A comparison of the linear and polynomial regression was applied to analyze the impedance ratio as a function of glucose concentrations. The proposed glucose paper sensor showed a limit of detection (LoD) of 1.135 mM. This novel and non-enzymatic paper sensor suggests a low-cost glucose test assay and can improve the quality of routine testing for diabetic patients.

For the hundreds of millions of worldwide diabetic patients, glucose test strips are the most important and commonly used tool for monitoring blood glucose levels. Commercial test strips use glucose oxidases as recognition agents, which increases the cost and reduces the durability of test strips. To lower the cost of glucose sensors, we developed a paper-based electrical sensor with molecularly imprinted glucose recognition sites and demonstrated the determination of various glucose concentrations in bovine blood solutions. The sensing electrode is integrated with molecular recognition sites in the conductive polymer. A calibration graph as a function of glucose concentration in aqueous solution was acquired and matched with a correlation coefficient of 0.989. We also demonstrated the determination of the added glucose concentrations ranging from 2.2 to 11.1 mM in bovine blood samples with a linear correlation coefficient of 0.984. This non-enzymatic glucose sensor has the potential to reduce the health care cost of test strips as well as make glucose sensor test strips more accessible to underserved communities.

Perfluorinated compounds like perfluorooctanesulfonic acid (PFOS) are synthetic water pollutants and have accumulated in environments for decades, causing a serious global health issue. Conventional assays rely on liquid chromatography and mass spectroscopy that are very expensive and complicated and thus limit the large-scale monitoring of PFOS in wastewater. To achieve low-cost and accurate detection of PFOS, we designed a paper-based sensor with molecularly imprinted polyaniline electrodes that have recognition sites specific to PFOS. The calibration curve of resistivity ratios as a function of PFOS concentrations has a linear range from 1 to 100 ppt with a coefficient of determination of 0.995. The estimated limit of detection is 1.02 ppt. We also investigated attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) spectra of the surface of the polyaniline (PANI) electrodes to propose the potential recognition sites in polyaniline matrix and the detection mechanism. This electrical paper sensor with low cost and excellent sensitivity and selectivity provides the potential for large-scale monitoring of wastewater.

While monoclonal antibodies are the fastest-growing class of therapeutic agents, we lack a method that can directly quantify the on- and off-target binding affinities of newly developed therapeutic antibodies in crude cell lysates. As a result, some therapeutic antibody candidates could have a moderate on-target binding affinity but a high off-target binding affinity, which not only gives a reduced efficacy but triggers unwanted side effects. Here, we report a single-molecule counting method that precisely quantifies antibody-bound receptors, free receptors, and unbound antibodies in crude cell lysates, termed digital receptor occupancy assay (DRO). Compared to the traditional flow cytometry-based binding assay, DRO assay enables direct and digital quantification of the three molecular species in solution without the additional antibodies for competitive binding. When characterizing the therapeutic antibody, cetuximab, using DRO assay, we found the on-target binding ratio to be 65% and the binding constant (Kd) to be 2.4 nM, while the off-target binding causes the binding constant to decrease by 0.3 nM. Other than cultured cells, the DRO assay can be performed on tumor mouse xenograft models. Thus, DRO is a simple and highly quantitative method for cell-based antibody binding analysis which can be broadly applied to screen and validate new therapeutic antibodies.

Extracellular vesicles (EVs) play an important role in intercellular communication. Recently, there has been increasing interest in EVs as potential diagnostic biomarkers and therapeutic vehicles. However, the molecular properties and cargo information of EV subpopulations have not yet been fully investigated due to lack of reliable and reproducible EV separation technology. Current approaches have faced difficulties with efficiently isolating EVs from biofluids, especially subpopulations of small EVs. Here, we report an EV isolation method based on a size-selective microfluidic platform (ExoSMP) via nanomembrane filtration and electrophoretic force. This unique platform offers an enhanced approach to sorting a heterogeneous population of EVs based on size, with the additional advantages of being label-free and low-cost, and featuring a short processing time (<1 h), and convenient integration with downstream analysis. In this research, we used ExoSMP to demonstrate the isolation of cancer-derived small EVs (30-120 nm) with high recovery (94.2%) and reproducibility at an optimum sample flow rate. Furthermore, we investigated isolation of EV subpopulations by altering nanomembrane combinations with different pore size combinations (50 and 100 nm, 30 and 100 nm, 30 and 200 nm, and 30 and 50 nm). This ExoSMP technique can serve as a standardized EV isolation/separation tool, facilitating the clinical prospects of EVs and opening up a new avenue for future point-of-care applications in liquid biopsies.

Exosomes are nanosized extracellular vesicles that play a significant role in cell-cell communication. Recently, there is significant interest in exosome-related fundamental research, especially subgroups of exosomes as potential biomarkers for cancer diagnosis and prognosis. In this paper, we report a new size selective isolation method via elastic lift force and nanomembrane filtration and demonstrated the liposome recovery rate of 92.5% from a mixture solution of 1 pm polystyrene beads, 100 nm liposomes and proteins as a proof of concept for exosome isolation. This single microfluidic platform offers an improved approach with short processing time (< 2 hours) and low cost, and shows potential broad applicability to cancer biomarker studies.

We have developed an acoustic frequency driven microbubble motor (AFMO) device and achieved highspeed rotation up to 450 RPM and torque of 2.3 x 10-9 (N.m). Additionally, the bidirectional rotation of this device has been demonstrated by modulating input frequencies. This device, directly constructed from UV curable resin by a micro-3D printer, has four microscale cavities that contain micro air bubbles when immersed in water. Once external 4 kHz acoustic waves stimulate these four cavities, microbubbles are extracted and positioned at the entrances of the cavities. These four microbubbles have identical dimensions and oscillation resonant frequencies of 5.6 kHz based on theoretical calculations that can spin the AFMO device in a clockwise direction. Both the clockwise and the counterclockwise rotation of the AFMO device have observed at a 5.6 and 5.1 kHz frequency input, respectively. Published by Elsevier B.V.

Per- and poly-fluoroalkyl substances (PFASs) are man-made chemicals that are toxic and widely detected in the environment, including drinking water sources. A cost-effective treatment process for PFASs is currently not available. We developed reusable hydrogel sorbents to remove long- and short-chain perfluoroalkyl acids and 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)propanoic acid (GenX), which is are emerging PFAS. Through fluoridation and amination of poly(ethylene glycol) diacrylate (PEGDA), the newly synthesized sorbents can sorb the five targeted PFASs (perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorobutanesulfonic acid (PFBS), and perfluorobutanoic acid (PFBA) and GenX) to different degrees from aqueous solution. Aminated PEGDA showed the highest sorption capacity for all five PFASs, particularly for PFBA and PFBS. The bifunctionalized PEGDA showed higher capacities for PFOA and PFOS, suggesting that both hydrophobic interactions and charges contribute to the sorption. Both aminated and bifunctionalized sorbents can remove GenX from water, with the highest sorption capacity of 98.7 μmol g aminated PEGDA-1 within 6 h. The absorbed PFASs on the sorbents were observed and characterized by Fourier-transform infrared spectroscopy. The spent sorbents were reusable after readily regenerated with 70% methanol contained 1% NaCl.

Protein expression level is critically related to the cell physiological function. However, current methodologies such as Western blot (WB) and Immunohistochemistry (IHC) in analyzing the protein level are rather semi-quantitative and without the information of actual protein concentration. We have developed a microfluidic technique termed a "flow-proteometric platform for analyzing protein concentration (FAP)" that can measure the concentration of a target protein in cells or tissues without the requirement of a calibration standard, e.g., the purified target molecules. To validate our method, we tested a number of control samples with known target protein concentrations and showed that the FAP measurement resulted in concentrations that well matched the actual concentrations in the control samples (coefficient of determination [R2], 0.998), demonstrating a dynamic range of concentrations from 0.13 to 130 pM of a detection for 2 min. We successfully determined a biomarker protein (for predicting the treatment response of cancer immune check-point therapy) PD-L1 concentration in cancer cell lines (HeLa PD-L1 and MDA-MB-231) and breast cancer patient tumor tissues without any prior process of sample purification and standard line construction. Therefore, FAP is a simple, faster, and reliable method to measure the protein concentration in cells and tissues, which can support the conventional methods such as WB and IHC to determine the actual protein level.

Collagen microparticles have recently gained more attention as viable cell confinement blocks in many biomedical research fields. Small volume and high surface area of collagen structure improve cell confinement, viability, and proliferation. Moreover, dense collagen fiber structure can protect cells from immune destruction. The ability to produce collagen microparticles in an accurate and reliable way is of upmost importance to the advancement of many biomedical researches, especially cancer research and tissue engineering. Currently, no such fabrication technique exists due to inherent fragility of collagen. Herein, we report the very first platform, pneumatically actuated soft micromold (PASMO) device, which addresses challenges in collagen microparticle production. Our new platform uses a soft micromold with a pneumatic actuator that can produce arbitrary shapes of collagen microstructures precisely from 100 μm to over 2 mm in range and can encapsulate cells inside without damaging the shape. The duplication accuracy of more than 96% in dimensions and 90% in depth has been demonstrated. The density of collagen fiber distribution is determined to be 86.57%, which is higher than that of collagen microparticles produced by other methods. We have confirmed cell viability in collagen microparticles. We also produce Matrigel™ particles as tool to develop a xenograft cancer model. The results demonstrate that Matrigel particles created by the PASMO device can reduce cell scattering for the xenograft model and the uniformity of tumors developed in mice is 12-fold improved, which can lead to an increased accuracy of cancer metastasis studies and drug screening research. These breakthroughs in the production of modular microparticles will push the boundaries of cancer research in the near future.

A miniaturized wideband interferometry-based sensor for complex dielectric spectroscopy of liquid chemicals is presented in this paper. Two composite right-/left-hand (CRLH) transmission lines (TLs) are employed in a direct downconversion architecture. The material under test (MUT) is placed in direct contact with the printed interdigital capacitor of the artificial TL as the sensing component. Since the employed CRLH TL provides nonlinear dispersion characteristics, improved sensitivity with wideband (4.2-8 GHz) operation is achieved compared with resonator-or TL-based interferometers. The sensor circuit board is realized based on common printed circuit board technology, and the fluidic polydimethylsiloxane channels are fabricated and bonded to the circuit board using 3-D printing and soft lithography techniques. The measured results of pure liquid chemical characterization suggest the mean squared errors of similar to 1.1% and similar to 1.6% for epsilon(r)' and epsilon(r)", respectively, compared with the MUT's theoretical model. Moreover, binary mixture characterization is carried out based on epsilon(r)' measurements with an accuracy of 1%.

A microfluidic device utilizing magnetically activated nickel (Ni) micropads has been developed for controlled localization of plasmonic core-shell magnetic nanoparticles, specifically for surface enhanced Raman spectroscopy (SERS) applications. Magnetic microfluidics allows for automated washing steps, provides a means for easy reagent packaging, allows for chip reusability, and can even be used to facilitate on-chip mixing and filtration towards full automation of biological sample processing and analysis. Milliliter volumes of gold-coated 175-nm silica encapsulated iron oxide nanoparticles were pumped into a microchannel and allowed to magnetically concentrate down into 7.5 nl volumes over nano-thick lithographically defined Ni micropads. This controlled aggregation of core-shell magnetic nanoparticles by an externally applied magnetic field not only enhances the SERS detection limit within the newly defined nanowells but also generates a more uniform (∼92%) distribution of the SERS signal when compared to random mechanical aggregation. The microfluidic flow rate and the direction and strength of the magnetic field determined the overall capture efficiency of the magneto-fluidic nanoparticle trapping platform. It was found that a 5 μl/min flow rate using an attractive magnetic field provided by 1 × 2 cm neodymium permanent magnets could capture over 90% of the magnetic core-shell nanoparticles across five Ni micropads. It was also observed that the intensity of the SERS signal for this setup was 10-fold higher than any other flow rate and magnetic field configurations tested. The magnetic concentration of the ferric core-shell nanoparticles causes the SERS signal to reach the steady state within 30 min can be reversed by simply removing the chip from the magnet housing and sonicating the retained particles from the outlet channel. Additionally, each magneto-fluidic can be reused without noticeable damage to the micropads up to three times.

Rapid assessment of radiation exposure to sensitive organs like the gut is extremely important for large populations exposed to ionized radiation, for instance during warfare. Recent results have shown that plasma citrulline levels appear to track gut function after irradiation levels in mice and humans. The current ways to monitor blood citrulline levels are bulky, laborious, time-consuming and expensive methods. Therefore, an optofludic point-of-care (POC) system using surface enhanced Raman spectroscopy to measure plasma citrulline as a marker for radiation exposure that overcomes the above issues is being developed.As a first step toward development of this system four colloidal nanoparticles, spherical gold, silver cubes, silica-gold nanoshells, and silver-gold nanocages have been analyzed for use in the POC system. Transmission electron microscopy (TEM) images have been taken of each nanoparticle to visualize the morphology of the nanoparticles, which is vital for SERS. Ultraviolet-visible (UV/Vis) spectroscopy was also collected to verify the extinction spectra for each nanoparticle was in resonance with the excitation wavelength. The nanoparticles were functionalized with mercaptobenzoic acid (MBA), a Raman reporter molecule, and SERS spectra were collected to determine which has better utility in a novel micro-to-nanochannel. The data showed that the silver nanocubes have a larger enhancement factor than the gold nanospheres, nanoshells, or nanocages. Currently, these nanocubes are being functionalized with the citulline for assessing the concentration sensitivity and dynamic range for ultimate use as a marker for radiation.

Signal transductions including multiple protein post-translational modifications (PTM), protein-protein interactions (PPI), and protein-nucleic acid interaction (PNI) play critical roles for cell proliferation and differentiation that are directly related to the cancer biology. Traditional methods, like mass spectrometry, immunoprecipitation, fluorescence resonance energy transfer, and fluorescence correlation spectroscopy require a large amount of sample and long processing time. "microchannel for multiple-parameter analysis of proteins in single-complex (mMAPS)" we proposed can reduce the process time and sample volume because this system is composed by microfluidic channels, fluorescence microscopy, and computerized data analysis. In this paper, we will present an automated mMAPS including integrated microfluidic device, automated stage and electrical relay for high-throughput clinical screening. Based on this result, we estimated that this automated detection system will be able to screen approximately 150 patient samples in a 24-hour period, providing a practical application to analyze tissue samples in a clinical setting.

We have developed a 3D coaxial flow-focusing nozzle device for the mass production of monodispersed collagen microspheres and chemically crosslinked them using EDC (1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide) and N-hydroxysuccinimide (NHS). The size of the microspheres was varied between 200 mu m and 600 mu m by adjusting the ratio of the flow rates of the dispersed and continuous phases. MDA231-GFP cells were attached to the surface of these particles and their viability was investigated. Because they are comprised of a natural biomaterial, these collagen microspheres will have numerous applications, including bone regeneration scaffolds for tissue engineering and analyses of cancer cell interactions in a 3D environment.

Conjugation of oligonucleotides or aptamers and their corresponding analytes onto plasmonic nanoparticles mediates the formation of nanoparticle assemblies: molecularly bound bundles of nanoparticles which cause a measurable change in the colloid's optical properties. Here, we present further optimization of a "SERS off" competitive binding assay utilizing plasmonic and magnetic nanoparticles for the detection of the toxin bisphenol A (BPA). The assay involves 1) a 'target' silver nanoparticle functionalized with a Raman reporter dye and PEGylated BPA-binding DNA aptamers, and 2) a version of the toxin BPA, bisphenol A diglycidyl ether (BADGE), PEGylated and immobilized onto a silver coated magnetic 'probe' nanoparticle. When mixed, these target and probe nanoparticles cluster into magnetic dimers and trimers and an enhancement in their SERS spectra is observed. Upon introduction of free BPA in its native form, target AgNPs are competitively freed; reversing the nanoparticle assembly and causing the SERS signal to "turn-off" and decrease in response to the competitive binding event. The assay particles were housed inside two types of optofluidic chips containing magnetically active nickel pads, in either a straight or spotted pattern, and both Fe2O3 and Fe2CoO4 were compared as magnetic cores for the silver coated probe nanoparticle. We found that the Ag@ Fe2O3 particles were, on average, more uniform in size and more stable than Ag@ Fe2CoO4, while the addition of cobalt significantly improved the collection time of particles within the magnetic chips. Using 3D Raman mapping, we found that the straight channel design with the Ag@ Fe2O3 particles provided the most uniform nanoparticle organization, while the spotted channel design with Ag@ Fe2CoO4 demonstrated a larger SERS enhancement, and thus a lower limit of detection.

A new method to fluidically switch through via posts is proposed for the first time. The reconfigurable via post is used toward designing a switchable QMSIW antenna. The switching method is based on filling/emptying a non-plated via hole with/from a liquid metal alloy. A QMSIW antenna is designed to initially work at similar to 3.2 GHz. Connecting the fluidically switchable via post at the corner of the QMSIW antenna shifts up the operating frequency. This translates into a switching range of 3.2-4.7 GHz. The Polydimethylsiloxane (PDMS) structures including the micro-channels are bonded to the QMSIW circuit board using a unique fabrication technique.

This paper presents a miniature wide-band interferometry sensor for dielectric spectroscopy and detection of liquid chemicals based on utilizing two composite right/lefthanded (CRLH) transmission lines (TLs) in a zero-IF mixing configuration. The equivalent series capacitance of the CRLH TLs, constructed by using microstrip interdigital capacitors, is loaded with microfluidic channels, and exposed to the material under test (MUT) to act as the sensing element. Due to the nonlinear dispersion relation of the artificial TLs with respect to the sensing capacitor, higher sensitivity over a frequency band as wide as 4-8 GHz is achieved, compared to the previously-reported resonator-or capacitor-based sensors. The final fabricated system prototype is 4 cmx8 cm. Moreover, a calibration method is presented based on measurement results, which shows an rms error less than similar to 1.5% for liquid-chemical permittivity detection. To the best of author's knowledge, this is the first disclosure of wide-band and highly-sensitive microwave interferometry sensor suitable for portable lab-on-board applications.

Reconfiguration of filled and empty microchannels is used to realize a switchable dual-band slot antenna whose both bands can be controlled independently. Reactive loading effect of Galinstan bridges is used to shift down each slot antenna's frequency of operation. Using five microchannels results in a 5-bit reconfigurable antenna. Any combination of frequencies within the ranges of 1.8-3.1 GHz (first band) and 3.2-5.4 GHz (second band) can be obtained. This translates into a discrete tuning ratio of for both bands and overall ratio of 3: 1 (1.8-5.4 GHz) for the antenna. The antenna circuit board is realized using common printed circuit board (PCB) techniques, and the microchannels' polydimethylsiloxane (PDMS) substrate is fabricated using 3-D printing technologies. The circuit board and the PDMS substrates are bonded to each other using a thin layer of spin-coated PDMS. The performance of the antenna is measured, and close agreement between the simulation and measurement is observed.

Signal transduction is essential for maintaining normal cell physiological functions, and deregulation of signaling can lead to diseases such as diabetes and cancers. Some of the major players in signal delivery are molecular complexes composed of proteins and nucleic acids. This unit describes a technique called microchannel for multiparameter analysis of proteins in a single complex (mMAPS) for analyzing and quantifying individual target signaling complexes. mMAPS is a flow-proteometric system that allows detection of individual proteins or complexes flowing through a microfluidic channel. Specific target proteins and nucleic acids labeled by fluorescent tags are harvested from tissues or cultured cells for analysis by the mMAPS system. Overall, mMAPS enables both detection of multiple components within a single complex and direct quantification of different populations of molecular complexes in one setting in a short timeframe and requiring very low sample input.

A micro- to nanochannel nanoparticle aggregating device that does not require any input energy to organize the particles to a specific location, i.e., no pumps, plugs, heat, or magnets, has been designed and used to characterize the surface-enhanced Raman spectroscopy (SERS) signal from four unique functionalized nanoparticles (gold, silver-gold nanocages, silver nanocubes, and silica-gold nanoshells). The SERS signal was assessed in terms of the peak signal strength from the four different Raman reporter functionalized nanoparticles to determine which nanoparticle had better utility in the channel to provide the most robust platform for a future biological analyte detection device. The innovation used to fabricate the micro- to nanochannel device is described; the TEM images of the nanoparticles are shown; the absorption data for the nanoparticles are given; and the spectral data for the Raman reporter, mercaptobenzoic acid (MBA), are depicted. In the micro- to nanochannel described in this work, 5  μl of 22.3  μM MBA functionalized silver nanocubes were determined to have the strongest SERS enhancement.

Conjugation of aptamers and their corresponding analytes onto plasmonic nanoparticles mediates the formation of nanoparticle assemblies: molecularly bound nanoclusters that cause a measurable change in the colloid’s optical properties. The optimization of a surface-enhanced Raman spectroscopy (SERS) competitive binding assay utilizing plasmonic “target” and magnetic “probe” nanoparticles for the detection of the toxin bisphenol-A (BPA) is presented. These assay nanoclusters were housed inside three types of optofluidic chips patterned with magnetically activated nickel pads, in either a straight or array pattern. Both Fe 2 O 3 and Fe 2 CoO 4 were compared as potential magnetic cores for the silver-coated probe nanoparticles. We found that the Ag @ Fe 2 O 3 particles were, on average, more uniform in size and more stable than Ag @ Fe 2 CoO 4 , whereas the addition of cobalt significantly improved the collection time of particles. Using Raman mapping of the assay housed within the magnetofluidic chips, it was determined that a 1 × 5 array of 50 ?? ? m square nickel pads provided the most uniform SERS enhancement of the assay (coefficient of variation ? 25 % ) within the magnetofluidic chip. Additionally, the packaged assay demonstrated the desired response to BPA, verifying the technology’s potential to translate magnetic nanoparticle assays into a user-free optical analysis.

We have developed a 3D dry lift-off process to localize multiple types of nitrifying bacteria in polyethylene glycol diacrylate (PEGDA) cubes for enhanced nitrification, a two-step biological process that converts ammonium to nitrite and then to nitrate. Ammonia-oxidizing bacteria (AOB) is responsible for converting ammonia into nitrite, and nitrite-oxidizing bacteria (NOB) is responsible for converting nitrite to nitrate. Successful nitrification is often challenging to accomplish, in part because AOB and NOB are slow growers and highly susceptible to many organic and inorganic chemicals in wastewater. Most importantly, the transportation of chemicals among scattered bacteria is extremely inefficient and can be problematic. For example, nitrite, produced from ammonia oxidation, is toxic to AOB and can lead to the failure of nitrification. To address these challenges, we closely localize AOB and NOB in PEGDA cubes as microenvironment modules to promote synergetic interactions. The AOB is first localized in the vicinity of the surface of the PEGDA cubes that enable AOB to efficiently uptake ammonia from a liquid medium and convert it into nitrite. The produced nitrite is then efficiently transported to the NOB localized at the center of the PEGDA particle and converted into non-toxic nitrate. Additionally, the nanoscale PEGDA fibrous structures offer a protective environment for these strains, defending them from sudden toxic chemical shocks and immobilize in cubes. This engineered microenvironment cube significantly enhances nitrification and improves the overall ammonia removal rate per single AOB cell. This approach-encapsulation of multiple strains at close range in cube in order to control their interactions-not only offers a new strategy for enhancing nitrification, but also can be adapted to improve the production of fermentation products and biofuel, because microbial processes require synergetic reactions among multiple species.

A microfiuidically-tunable substrate integrated cavity filter is presented for the first time. Quarter mode cylindrical substrate integrated waveguide (SIW) cavities are used to design an ultra-compact two-pole filter with a center frequency of similar to 1.12 GHz. A corner via is connected to a surface ring gap in order to capacitively load each SIW cavity resonator. Frequency tuning of the filter is achieved using the capacitive loading effect of a liquid metal channel placed on top of the surface gap capacitors. The Polydimethylsiloxane (PDMS) structure including the micro-channel is bonded to the SIW circuit board using a unique fabrication technique. Measured results verify a tuning ratio of 1.72:1 and an insertion loss of 2.5 and 3.45 dB at 1.12 and 0.65 GHz, respectively.

Microfluidic channels filled with liquid metal are used to realize miniature and reconfigurable CPW folded slot antennas. The method is based on employing the reactive loading effect of fluid metal bridges on top of the CPW slot antenna. As a result of this reactive loading, the frequency of the antenna reduces and the antenna is miniaturized by a factor of 85%. Also, by changing the configuration of filled and empty channels, each channel can be used as a switch. By using two pairs of microfluidic channels, three different frequency bands of 2.4, 3.5, and 5.8 GHz can be achieved. This translates to a switching ratio (f(TR) = f(2)/ f(1)) of more than 2.5. The antenna is realized using common PCB techniques for the antenna circuit board and three-dimensional (3-D) printing technology for PDMS-based microfluidics structure. The antenna circuit board and the PDMS structure are bonded to each other using a very thin spin-coated PDMS layer. Design methodology, simulation, and measurement results of both antenna prototypes are presented. Both the miniature and reconfigurable antennas have similar radiation patterns to a normal CPW folded slot antenna and show low cross-polarization levels at all operating frequencies.

In this paper, a microfluidically reconfigurable coplanar waveguide (CPW) filter is presented with a tuning range of similar to 1.6:1 and four different states. The passband frequency of the filter is changed based on employing the capacitive loading effect of a liquid metal placed on top of each CPW resonator using three parallel micro-channels. In addition, because of the loading effect of the metal bridges, miniaturization by a factor of 40% is achieved. The filter is digitally tuned from 3.4 to 5.5 GHz with an insertion loss of less than 5.0 dB and a relative bandwidth of 5 +/- 0.35%. The RF power-handling capability of the filter is characterized using a customized measurement setup. It is observed that the filter can be used for input RF powers of up to similar to 20 W for short-duration excitation conditions and 10 W for high-average-power excitation conditions. The filter is realized using common printed circuit board technology and a polydimethylsiloxane structure. Design methodology, simulation, and measurement results of the filter prototype are presented.

In this presentation we will discuss the development of a point-of-care optofluidic device that uses gold nanoparticle-based surface enhanced Raman spectroscopy (SERS) for detection of blood biomarkers. SERS approaches have been successfully used for detection of analytes due to the large enhancements provided by the interaction between the light, gold particles, and analyte. However, SERS approaches developed for use to accurately quantify an analyte have suffered from a lack of repeatability. We will describe our SERS optofluidic device with functionalized nanoparticles that helps to overcome these problems and will show results with a focus on blood cardiac biomarkers.

This paper presents two frequency tuning techniques, applied to planar microwave lumped LC and CPW resonators. Both methods are based on employing the reactive loading effect of a fluid metal placed on top of planar microwave circuits. The frequency tuning is achieved by moving the fluid metal inside the micro-channel and on top of different sections of each resonator. Realization of tunable resonators using common PCB technology and PDMS structure is demonstrated. The metal fluidic used is a non-toxic eutectic alloy of Gallium, Indium, and Tin known as Galinstan. Two implemented prototypes are measured and tuning ranges of 1.45-2.35 GHz and 2.8-3.9 GHz are achieved for lumped LC and CPW resonators, respectively.

A microfluidically-switched CPW folded slot antenna is proposed. The switching technique is based on employing the capacitive loading effect of two fluid metal channels placed on top of the CPW slot antenna. By filling the channels with Galinstan, the antenna is reactively loaded and as a result the resonant frequency of the antenna is reduced. Implementation of the microfluidically-switched antenna is realized using the common PCB techniques and PDMS structures. The PDMS structures including the micro-channels are bonded to the circuit board using a very thin layer of spin-coated PDMS employed as the bonding layer. A frequency switching ratio (f(TR)=f(2)/f(1)) of more than an octave (2.6-5.5 GHz) is obtained for the proposed antenna. The antenna shows similar radiation pattern with high purity (Co- to Cross polarization level > 15dB) for both frequency bands.

A reconfigurable dual-band slot antenna with the capability of independently controlling each band is proposed. The tuning method is based on employing the reactive loading effect of a fluid metal placed on top of each slot antenna. Digital frequency tuning is achieved by using different configurations of four empty and filled channels. This way a 4-bit reconfigurable antenna is achieved in which each resonant frequency of the dual-band response can be controlled separately. Realization of the tunable antenna using common PCB technologies and PDMS structure is demonstrated. The implemented prototype antenna is measured and tuning ranges of 2.2-3.3 GHz and 4.15-5.4 GHz are achieved for the first and second bands, respectively.

Signal transduction is a dynamic process that regulates cellular functions through multiple types of biomolecular interactions, such as the interactions between proteins and between proteins and nucleic acids. However, the techniques currently available for identifying protein-protein or protein-nucleic acid complexes typically provide information about the overall population of signaling complexes in a sample instead of information about the individual signaling complexes therein. We developed a technique called "microchannel for multiparameter analysis of proteins in a single complex" (mMAPS) that simultaneously detected individual target proteins either singly or in a multicomponent complex in cell or tissue lysates. We detected the target proteins labeled with fluorophores by flow proteometry, which provided quantified data in the form of multidimensional fluorescence plots. Using mMAPS, we quantified individual complexes of epidermal growth factor (EGF) with its receptor EGFR, EGFR with signal transducer and activator of transcription 3 (STAT3), and STAT3 with the acetylase p300 and DNA in lysates from cultured cells with and without treatment with EGF, as well as in lysates from tumor xenograft tissue. Consistent with the ability of this method to reveal the dynamics of signaling protein interactions, we observed that cells treated with EGF induced the interaction of EGF with EGFR and the autophosphorylation of EGFR, but this interaction decreased with longer treatment time. Thus, we expect that this technique may reveal new aspects of molecular interaction dynamics.

An amperometric cholesterol biosensor was fabricated using electrospun polyaniline nanofibers. Polyaniline was dissolved in chloroform with camphorsulfonic acid, and polystyrene was added in this solution. Using this mixed solution, nanofibers were formed and collected by electrospinning. Then cholesterol oxidase was immobilized onto these fibers using an electrostatic layer-by-layer adsorption technique. Poly(diallyldimethylammonium chloride) was used as the counter ion source. The level of adsorption was examined and evidence of layer-by-layer adsorption was investigated using a quartz crystal microbalance (QCM) technique. A cholesterol biosensor was fabricated from these nanofibers as a working electrode, and it was used to measure the cholesterol concentration. (C) 2011 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

A simple microfluidic 3D hydrodynamic flow focusing device has been developed and demonstrated quantitative determinations of quantum dot 525 with antibody (QD525-antibody) and hemagglutinin epitope tagged MAX (HA-MAX) protein concentrations. This device had a step depth cross junction structure at a hydrodynamic flow focusing point at which the analyte stream was flowed into a main detection channel and pinched not only horizontally but also vertically by two sheath streams. As a result, a triangular cross-sectional flow profile of the analyte stream was formed and the laser was focused on the top of the triangular shaped analyte stream. Since the detection volume was smaller than the radius of laser spot, a photon burst histogram showed Gaussian distribution, which was necessary for the quantitative analysis of protein concentration. By using this approach, a linear concentration curve of QD525-antibody down to 10 pM was demonstrated. In addition, the concentration of HA-MAX protein in HEK293 cell lysate was determined as 0.283 ± 0.015 nM. This approach requires for only 1 min determining protein concentration. As the best of our knowledge, this is the first time to determinate protein concentration by using single molecule detection techniques.

We have developed an integrated microfluidic material processing chip and demonstrated the rapid production of collagen microspheres encapsulating cells with high uniformity and cell viability. The chip integrated three material processing steps. Monodisperse microdroplets were generated at a microfluidic T junction between aqueous and mineral oil flows. The flow was heated immediately to 37 °C to initiate collagen fiber assembly within a gelation channel. Gelled microspheres were extracted from the mineral oil phase into cell culture media within an extraction chamber. Collagen gelation immediately after microdroplet generation significantly reduced coalescence among microdroplets that led to non-uniform microsphere production. The microfluidic extraction approach led to higher microsphere recovery and cell viability than when a conventional centrifugation extraction approach was employed. These results indicate that chip-based material processing is a promising approach for cell-ECM microenvironment generation for applications such as tissue engineering and stem cell delivery.

We have applied Raster Image Correlation Spectroscopy (RICS) technique to characterize the dynamics of protein 53 (p53) in living cells before and after the treatment with DNA damaging agents. HeLa cells expressing Green Fluorescent Protein (GFP) tagged p53 were incubated with and without DNA damaging agents, cisplatin or eptoposide, which are widely used as chemotherapeutic drugs. Then, the diffusion coefficient of GFP-p53 was determined by RICS and it was significantly reduced after the drug treatment while that of the one without drug treatment was not. It is suggested that the drugs induced the interaction of p53 with either other proteins or DNA. Together, our results demonstrated that RICS is able to detect the protein dynamics which may be associated with protein-protein or protein-DNA interactions in living cells and it may be useful for the drug screening.

We have developed a microfluidics based platform and methodology named MAPS (microfluidic system for analyzing proteins in single complex) for detecting two protein interactions rapidly using a single fluorophore. Target proteins were labelled with Quantum dot 525 (QD525) via specific polyclonal antibodies, and were transported through the microfluidic channel subsequently, where the 375 nm excitation laser light was focused to form a detection volume. Photon bursts from target proteins passing through the detection volume were recorded and their photon burst histograms were plotted which demonstrated roughly the specific protein interaction ratio based on their population and statistical behavior. As a proof of concept, Src/STAT3 protein complex interaction ratios with and without EGF stimulation were obtained by MAPS within 1 h and the results were well matched with the one obtained by the conventional immunoprecipitation/Western blot (IP/WB).

The understanding of protein interaction dynamics is important for signal transduction research but current available techniques prove difficult in addressing this issue. Thus, using the microfluidic approach, we developed a digital protein analytical platform and methodology named MAPS (Microfluidic system Analyzing Protein in Single complex) that can measure the amount of target proteins and protein complexes at the digitally single molecule resolution. By counting protein events individually, this system can provide rough protein interaction ratios which will be critical for understanding signal transduction dynamics. In addition, this system only requires less than an hour to characterize the target protein sample, which is much quicker than conventional approaches. As a proof of concept, we have determined the interaction ratios of oncogenic signaling protein complexes EGFR/Src and EGFR/STAT3 before and after EGF ligand stimulation. To the best of our knowledge, this is the first time that the interaction ratio between EGFR and its downstream proteins has been characterized. The information from MAPS will be critical for the study of protein signal transduction quantitation and dynamics.

The overall goal of this research is to develop a new point-of-care system for early detection and characterization of cardiac markers to aid in diagnosis of acute coronary syndrome. The envisioned final technology platform incorporates functionalized gold colloidal nanoparticles trapped at the entrance to a nanofluidic device providing a robust means for analyte detection at trace levels using surface enhanced Raman spectroscopy (SERS). To discriminate a specific biomarker, we designed an assay format analogous to a competitive ELISA. Notably, the biomarker would be captured by an antibody and in turn displace a peptide fragment, containing the binding epitope of the antibody labeled with a Raman reporter molecule that would not interfere with blood serum proteins. To demonstrate the feasibility of this approach, we used C-reactive protein (CRP) as a surrogate biomarker. We functionalized agarose beads with anti-CRP that were placed outside the nanochannel, then added either Rhodamine-6-G (R6G) labeled-CRP and gold (as a surrogate of a sample without analyte present), or R6G labeled CRP, gold, and unlabeled CRP (as a surrogate of a sample with analyte present). Analyzing the spectra we see an increase in peak intensity in the presence of analyte at characteristic peaks for R6G specifically, 1284 and 1567 cm-1. Further, our results illustrate the reproducibility of the Raman spectra collected for R6G-labeled CRP in the nanochannel. Overall, we believe that this method will provide the advantage of sensitivity and narrow line widths characteristic of SERS as well as the specificity toward the biomarker of interest.

Biomolecular transport in nanofluidic confinement offers various means to investigate the behavior of biomolecules in their native aqueous environments, and to develop tools for diverse single-molecule manipulations. Recently, a number of simple nanofluidic fabrication techniques has been demonstrated that utilize electrospun nanofibers as a backbone structure. These techniques are limited by the arbitrary dimension of the resulting nanochannels due to the random nature of electrospinning. Here, a new method for fabricating nanofluidic systems from size-reduced electrospun nanofibers is reported and demonstrated. As it is demonstrated, this method uses the scanned electrospinning technique for generation of oriented sacrificial nanofibers and exposes these nanofibers to harsh, but isotropic etching/heating environments to reduce their cross-sectional dimension. The creation of various nanofluidic systems as small as 20 nm is demonstrated, and practical examples of single biomolecular handling, such as DNA elongation in nanochannels and fluorescence correlation spectroscopic analysis of biomolecules passing through nanochannels, are provided.

We have developed a filter-chip and optical detection system for rapid antibiotic efficacy screening The filter-chip consisted of a 1-mL reservoir and an anodic aluminum oxide (MO) nanoporous membrane Sample solution with liquid growth media, bacteria, and antibiotics was incubated in the reservoir for a specific period of time The number of live bacteria on the surface of membrane was counted after the incubation with antibiotics and filtration. Using this biosensing system, we have demonstrated a 1-h antibiotic screening for patients' clinical samples, significantly faster than the conventional antibiotic susceptibility tests that typically take more than 24 h. This rapid screening nature makes the filter-chip and detection system ideal for tailoring antibiotic treatment to individual patients by reducing the microbial antibiotic resistance, and improving the survival rate for patients suffering from postoperative infections Published by Elsevier By.

According to the World Health Organization, cardiovascular disease is the most common cause of death in the world. In the US, over 115 million people visit the emergency department (ED), 5 million of which may have acute coronary syndrome (ACS). Cardiac biomarkers can provide early identification and diagnosis of ACS, and can provide information on the prognosis of the patient by assessing the risk of death. In addition, the biomarkers can serve as criteria for admission, indicate possibility of re-infarction, or eliminate ACS as a diagnosis altogether. We propose a SERS-based multi-marker approach towards a point-of-care diagnostic system for ACS. Using a nanofluidic device consisting of a microchannel leading into a nanochannel, we formed SERS active sites by mechanically aggregating gold particles (60 nm) at the entrance to the nanochannel (40 nmx1 mu m). The induced capillary flow produces a high density of aggregated nanoparticles at this precise region, creating areas with enhanced electromagnetic fields within the aggregates, shifting the plasmon resonance to the near infrared region, in resonance with incident laser wavelength. With this robust sensing platform, we were able to obtain qualitative information of brain natriuretic peptide (biomarker of ventricular dysfunction or pulmonary stress), troponin I (biomarker of myocardial necrosis), and C-reactive protein (biomarker of inflammation potentially caused by atherosclerosis).

An optofluidic device is reported in this paper that can highly improve the robustness of surface-enhanced Raman scattering (SERS) detection and provide fingerprint information of proteins with a concentration in the nanogram per liter range within minutes. Moreover, the conformational change of protein can also be obtained using this device. Fabricated by standard photolithography processes, the optofluidic device has a step microfluidic-nanofluidic structure, which provides robust SERS detection. The sensitivity of the device is investigated using insulin and albumin as target analytes at a concentration of 0.9 ng/L. The ability to detect conformational changes of proteins using this technology is also shown by probing these analytes before and after their denaturation.

An amperometric biosensor was fabricated using electospun composite nanofiber membra ne which are consisted of among polyaniline-polystylene nanofibers. Polyaniline was reacted with camphorsulfonic acid to produce a salt, which was then dissolved in chloroform containing polystyrene. By electrospinning this polymer solution, nanofibers were formed and collected at the counter electrodes. Glucose oxidase was immobilized onto these nanofiber matt using an electrostatic layer-by-layer adsorption technique. In this method, poly(diallyldimethylammonium chloride) was used as the counter ion source. The electrical property of this composite nanofiber was investigated from these nanofibers as a working electrode, and used to measure the glucose concentration accurately.

Alzheimer's disease (AD), a neurodegenerative disease and the most common cause of dementia, affects 4.5 million people according to the 2000 US census and is expected to triple to 13.2 million by the year 2050. Since no definitive pre-mortem. tests exist to distinguish AD from mild cognitive impairment due to the natural aging process, we focus on detecting the beta amyloid (A beta) protein, the primary component of the senile plaques characteristic of AD. We specifically detect cytotoxic species of A beta by exploiting surface enhanced Raman scattering (SERS). Using a nanofluidic device with a bottleneck shape (a microchannel leading into a nanochannel); we trapped gold colloid particles (60 nm) at the entrance to the nanochannel, with A beta restricted within the interstices between the aggregated nanoparticles. The continuous flow generated from pumping the solution into the device produced size-dependent trapping of the gold colloid particles, resulting in a high density of aggregated nanoparticles at this precise region, creating localized "hot spots" in the interstitial region between nanoparticles, and shifting the plasmon resonance to the near infrared region, in resonance with incident laser wavelength. With this robust sensing platform, we were able to obtain concentration-dependent SERS spectra of A beta and of different proteins that would be present in the cerebrospinal fluid of healthy people and people with Alzheimer's disease.

Cross-linked hydrogel features have been patterned using subtractive lift-off of polymerized hydrogel film. Projection lithography and oxygen plasma etch was used to pattern parylene C polymer film. Molecular self-assembly of polymerizable monolayer was obtained in solution-phase and acrylamide based hydrogel was polymerized using free-radical polymerization on this substrate. Parylene C film was mechanically lifted-off to remove the blanket hydrogel film and micro hydrogel features (mu hf) were obtained attached to the predefined patterns in the range from 1 to 60 mu m. The mu hf were functionalized with aldehyde functional groups, and proteins were coupled to them using Schiff base chemistry followed by reductive amination. Interaction of mesenchymal stem cells with transforming growth factor-beta 1 (TGF-beta 1) functionalized mu hf was studied, and TGF-beta 1 was found to retain its tumor suppression activity.

A 44-pass fibre-optic surface plasmon resonance sensor that enhances detection sensitivity according to the number of passes is demonstrated for the first time. The technique employs a fibre-optic recirculation loop that passes the detection spot 44 times, thus enhancing sensitivity by a factor of 44. Presently, the total number of passes is limited by the onset of lasing action of the recirculation loop. This technique offers a significant sensitivity improvement for various types of plasmon resonance sensors that may be used in chemical and biomolecule detections.

The Raman scattering signature of molecules has been demonstrated to be greatly enhanced, on the order of 10(6)-10(12) times, on roughened metal surfaces and clustered structures such as aggregated colloidal gold. Here we describe a method that improves reproducibility and sensitivity of the substrate for surface enhanced Raman spectroscopy (SERS) by using a nanofluidic trapping device. This nanofluidic device has a bottle neck shape composed of a microchannel leading into a nano channel that causes size-dependent trapping of nanoparticles. The analyte and Au nanoparticles, 60 nm in diameter, in aqueous solution was pumped into the channel. The nanoparticles which were larger than the narrow channel are trapped at the edge of the channel to render an enhancement of the Raman signal. We have demonstrated that the Raman scattering signal enhancement on a nanochannel-based colloidal gold cluster is able to detect 10 pM of adenine, the test analyte, without chemical modification. The efficiency and robustness of the device suggests potential for single molecule detection and multicomponent detection for biological applications and/or biotoxins.

We demonstrated a new technique to sort nanoparticles based on their dimensions. Due to the interactions between charged droplets and a nonlinear electrostatic field, nanoparticles with different dimensions were deposited at different spatial locations on a given target substrate. By using this principle, we have been able to sort nanocups into three groups with mean diameters of 0.31 mu m, 0.7 mu m, and 1.1 mu m and a standard deviation of 20%. This technique improves the nanoparticle fabrication process not only by decreasing the standard deviation of its dimensions but also by increasing its yield since nanoparticles with different mean diameters can be generated at the same time. Copyright (c) 2007.

We have developed an optofluidic device that improves the sensitivity of surface enhanced Raman spectroscopy (SERS) when compared to other SERS approaches. This device has a pinched and step microchannel-nanochannel junction that can trap and assemble nanoparticles/target molecules into optically enhanced SERS active clusters by using capillary force. These SERS active clusters provide an electromagnetic enhancement factor of similar to 10(8). In addition, due to the continuous capillary flow that can transport nanoparticles/target molecules into the junction sites, the numbers of nanoparticles/target molecules and SERS active sites are increased. As a result, the detection limit of SERS for adenine molecules was better than 10 pM.

A fiber optic four-pass surface plasmon resonance technique with an approach to increase the number of passes to any arbitrary number is described. Within multipass regime, reflections off the gold sample surface that reduce the reflectivity to less than 0.1% are achieved by using a fiber optic collimator, a reflector, and a corner cube prism. In this case, the optical beam emits from and returns to the collimator. This technique holds the potential for significantly increasing the detection sensitivity of surface plasmon resonance device.