Enhanced electrophoresis separation of non-electroactive amino acids on poly(dimethylsiloxane) microchip coupled with direct electrochemical detection on a copper electrode

Electrochemical determination of amino acids on a Cu electrode was established as an attractive scheme for non-electroactive amino acids after microchip electrophoresis separation. Five amino acids (arginine, proline, histidine, valine, and serine) achieved efficient separation within 60 s on a titanium dioxide nanoparticles (TiO₂ NPs) coated poly(dimethylsiloxane) (PDMS) microchip, and then successfully detected on a Cu electrode in end-channel detection mode. In the slightly basic borate medium, anodic currents occur for amino acids due to their ability to form Cu(II) complexes and thereby enhance the electrochemical dissolution of Cu electrode substrate. The increase of the anodic current measured is proportional to the amino acid concentration added to the solution, and therefore, enables direct detection of non-electroactive amino acids on the Cu electrode. The detection limits (S/N = 3) for arginine, proline, histidine, valine, and serine were measured to be 7, 6, 5, 6, and 5 μM, respectively, with the linear ranges all from 25 to 500 μM. In addition, compared with the native PDMS microchip, resolutions and separation efficiencies of amino acids on the modified microchip were considerably enhanced with the theoretical plate numbers of 8.9 × 10³, 6.6 × 10⁴, 4.8 × 10⁴, 5.6 × 10⁴, and 4.4 × 10⁴ plates m⁻¹, respectively. The proposed Cu electrode response demonstrated good reproducibility and stability, with no apparent loss of response for periods as long as 4 weeks.     

Chemiluminescence detection for Cu (II) based on 1,10-Phenanthroline-hydrogen peroxide reaction on a PDMS microfluidic chip

A simple, rapid and effective method for the determination of copper (II) in water on a PDMS microfluidic chip with chemiluminescence (CL) detection is presented. The CL reaction was based on oxidation of 1,10-phenanthroline by hydrogen peroxide in basic aqueous solution. Polydimethylsiloxane (PDMS) was chosen as material for fabricating the microfluidic chip with two steps lithography method. Optimized reagents conditions were found to be 6.0 × 10^?5 mol/L 1,10-phenanthroline, 1.2 × 10^?3 mol/L hydrogen peroxide, 6.5 × 10^?2 mol/L sodium hydroxide and 2.0 × 10^?3 mol/L Hexadecyl trimethyl ammonium Bromide (CTMAB). In the continuous flow injection mode the system can perform fully automated detection with a reagent consumption of only 3.4 μL each time. The linear range of the Cu (II) ions concentration was 1.0 × 10^?8 mol/L to 1.0 × 10^?4 mol/L, and the detection limit was 9.2 × 10^?9 mol/L with the S/N ratio of 3. The relative standard deviation was 2.8 % for 1.0 × 10^?6 mol/L Cu (II) ions (n = 8). The most notable features of the detection method are simple operation, rapid detection and easy fabrication of the microfluidic chip.     

John G. Fox (1931-2004)

The effectiveness of intermittent, microclimate cooling for men who worked in US Army chemical protective clothing (modified mission-oriented protective posture level 3; MOPP 3) was examined. The hypothesis was that intermittent cooling on a 2 min on–off schedule using a liquid cooling garment (LCG) covering 72% of the body surface area would reduce heat strain comparably to constant cooling. Four male subjects completed three experiments at 30°C, 30% relative humidity wearing the LCG under the MOPP 3 during 80 min of treadmill walking at 224 ± 5 W · m^?2. Water temperature to the LCG was held constant at 21°C. The experiments were; 1) constant cooling (CC); 2) intermittent cooling at 2-min intervals (IC); 3) no cooling (NC). Core temperature increased (1.6 ± 0.2°C) in NC, which was greater than IC (0.5 ± 0.2°C) and CC (0.5 ± 0.3°C) ( p < 0.05). Mean skin temperature was higher during NC (36.1 ± 0.4°C) than IC (33.7 ± 0.6°C) and CC (32.6 ± 0.6°C) and mean skin temperature was higher during IC than CC ( p < 0.05). Mean heart rate during NC (139 ± 9 b · min^?1) was greater than IC (110 ± 10 b · min^?1) and CC (107 ± 9 b · min^?1) ( p < 0.05). Cooling by conduction (K) during NC (94 ± 4 W · m^?2) was lower than IC (142 ± 7 W · m^?2) and CC (146 ± 4 W · m^?2) ( p < 0.05). These findings suggest that IC provided a favourable skin to LCG gradient for heat dissipation by conduction and reduced heat strain comparable to CC during exercise-heat stress in chemical protective clothing.     

Design and fabrication of poly(dimethylsiloxane) electrophoresis microchip with integrated electrodes

A novel poly(dimethylsiloxane) (PDMS) microchip integrated with platinum electrodes has been designed and fabricated using the Micro-electro-mechanical-systems (MEMS) technology. Since high voltage electrodes are integrated on the glass wafer using lift-off process, the microchip is a friendly-to-use system that does not need any extra mechanical apparatus for electrode insertion. To improve the sealing of microchip and ensure the uniformity of microchannel material, one PDMS membrane is formed on glass wafer with electrodes by pressing method. In this study, integrated microchip has been demonstrated as a capillary electrophoresis device for amino acids and satisfactory separation was achieved under separation electrical field strengths of 200 V/cm. The overall performance suggests that this novel microchip is advantageous and practical for the fabrication of lab-on-a-chip.     

Development of the automated gold-linked electrochemical immunoassay system for blood monitoring

This paper reports the development of fully automated miniaturized immunoassay system. The system consist of postage stamp sized microchip and compact (post card sized foot print) microchip driver. To realize easy sample loading into the microchip, surface modification of polydimethylsiloxane (PDMS) was developed, and life time of the modified surface up to 9 days is confirmed. The microchip just consumes a droplet of blood (2 μl) and the loading and metering of the sample is realized by capillary action, therefore the microchip is compatible with blood collection method by using lancet needle. Fully automated immunoassay protocol in the system is demonstrated within 15 min using whole blood sample. Finally, fully automated detection of antigen (insulin) was successfully demonstrated in the developed system.     

An effective PDMS microfluidic chip for chemiluminescence detection of cobalt (II) in water

A microfluidic chip for the chemiluminescence detection of cobalt (II) in water samples, based on the measurement of light emitted from the cobalt (II) catalysed oxidation of luminol by hydrogen peroxide in basic aqueous solution, is presented. The microfluidic chip was designed and fabricated from polydimethylsiloxane using micro-molding method. Optimized reagents conditions were found to be 5.0 × 10^?4 mol/L luminol, 1.0 × 10^?2 mol/L hydrogen peroxide, and 8.0 × 10^?2 mol/L sodium hydroxide. The system can perform fully automated detection with a reagent consumption of only 2.4 μL each time. The linear range of the cobalt (II) ions concentration was 1.0 × 10^?10–1.0 × 10^?3 mol/L and the detection limit was 5.6 × 10^?11 mol/L with the S/N ratio of 3. The relative standard deviation was 4.6 % for 1.0 × 10^?5 mol/L cobalt (II) ions (n = 10).     

Low-cost polymer microfluidic device for on-chip extraction of bacterial DNA

A polymer microfluidic device for on-chip extraction of bacterial DNA has been developed for molecular diagnostics. In order to manufacture a low-cost, disposable microchip, micropillar arrays of high surface-to-volume ratio (0.152 μm⁻¹) were constructed on polymethyl methacrylate (PMMA) by hot embossing with an electroformed Ni mold, and their surface was modified with SiO₂ and an organosilane compound in subsequent steps. To seal open microchannels, the organosilane layer on top plane of the micropillars was selectively removed through photocatalytic oxidation via TiO₂/UV treatment at room temperature. As a result, the underlying SiO₂ surface was exposed without deteriorating the organosilane layer coated on lateral surface of the micropillars that could serve as bacterial cell adhesion moiety. Afterwards, a plasma-treated PDMS substrate was bonded to the exposed SiO₂ surface, completing the device fabrication. To optimize manufacturing throughput and process integration, the whole fabrication process was performed at 6 inch wafer-level including polymer imprinting, organosilane coating, and bonding. Preparation of bacterial DNA was carried out with the fabricated PDMS/PMMA chip according to the following procedure: bacterial cell capture, washing, in situ lysis, and DNA elution. The polymer-based microchip presented here demonstrated similar performance to Glass/Si chip in terms of bacterial cell capture efficiency and polymerase chain reaction (PCR) compatibility.     

Variations of surface boundary layer parameters associated with Cyclone Gonu over the Arabian Sea using QuikSCAT data

This study attempted to quantify the variations of the surface marine atmospheric boundary layer (MABL) parameters associated with the tropical Cyclone Gonu formed over the Arabian Sea during 30 May–7 June 2007 (just after the monsoon onset). These characteristics were evaluated in terms of surface wind, drag coefficient, wind stress, horizontal divergence, and frictional velocity using 0.5° × 0.5° resolution Quick Scatterometer (QuikSCAT) wind products. The variation of these different surface boundary layer parameters was studied for three defined cyclone life stages: prior to the formation, during, and after the cyclone passage. Drastic variations of the MABL parameters during the passage of the cyclone were observed. The wind strength increased from 12 to 22 m s^?1 in association with different stages of Gonu. Frictional velocity increased from a value of 0.1–0.6 m s^?1 during the formative stage of the system to a high value of 0.3–1.4 m s^?1 during the mature stage. Drag coefficient varied from 1.5 × 10^?3 to 2.5 × 10^?3 during the occurrence of Gonu. Wind stress values varied from 0.4 to 1.1 N m^?2. Wind stress curl values varied from 10 × 10^?7 to 45 × 10^?7 N m^?3. Generally, convergent winds prevailed with the numerical value of divergence varying from 0 to –4 × 10^?5 s^?1. Maximum variations of the wind parameters were found in the wall cloud region of the cyclone. The parameters returned to normally observed values in 1–3 days after the cyclone passage.     

Rapid prototyping of magnetic valve based on nanocomposite Co/PDMS membrane

In this study, a new type of active membrane based on magnetic elastomer composite is manufactured, characterized and integrated into a simple valve. The simple and low-cost fabrication process combined with large displacement capability of the membrane is favorable for use in disposable fluidic devices. Passivated ferromagnetic cobalt nanoparticles (~37 nm) synthesized by the chemical route were embedded in polydimethylsiloxane (PDMS) to fabricate nano-composite flexible membranes. Magneto-mechanical and mechanical properties of the PDMS composite elastomeric membrane loaded with various concentrations of cobalt (Co) nanoparticles (between 15 and 75 % by weight) were studied. Dynamic mechanical analysis (DMA) measurements of the nano-composite membranes were conducted as a function of the applied frequency (between 0.1 and 56 Hz). With higher concentration (50-wt%) of Co nanoparticles in PDMS, the elastic modulus was increased by 3–4 times as compared with that of membranes with lower concentrations of nanoparticles. Shore hardness was maximum for the nano-composite membrane loaded with 50-wt% of Co nanoparticles. A fluidic actuator with 400 μm thick PDMS membrane of 18 mm free diameter loaded with 50-wt% Co nanoparticles was manufactured and tested under external magnetic field. In the region where the magnetic field gradient is highest, high deflection of the membrane could be obtained (0.68 mm for 1 Tesla). However some hysteresis of the membrane deflection could be observed, even at very low frequency. Loading of PDMS with Co nanoparticles allowed a wider range of control of the wetting properties of PDMS surfaces under oxygen plasma treatment, from hydrophobic to hydrophilic to super-hydrophilic. Tunability in hydrophilicity could be achieved by varying the process parameters as verified by contact angles and Fourier transforms infrared (FTIR) spectra before and after plasma treatment. Under certain conditions, 50 % Cobalt-PDMS membrane surfaces exhibited a super-hydrophilic behavior (contact angle ~5°).     

Particulate organic carbon in the surface waters of the North Atlantic: spatial and temporal variability based on satellite ocean colour

We have examined the 16-year time series of particulate organic carbon (POC) concentration in the surface waters of the North Atlantic derived from SeaWiFS and MODIS-Aqua data. The annual mean POC concentrations are the highest in the northern North Atlantic, reaching 120 mg m^?3. Moving south, the mean annual POC concentrations decrease to minimum values of about 30 mg m^?3 at around 30° N and increase in the equatorial region to about 70 mg m^?3. The seasonal amplitude of POC concentration in the northern North Atlantic region is larger when compared to other regions. The annual mean surface POC concentrations in the entire North Atlantic basin show a statistically significant trend with an average decrease of 0.79 mg m^?3 year^?1. Regionally averaged 16-year mean POC biomass integrated over the optical depth, euphotic depth, and mixed-layer depth is estimated at about 1.27, 4.34, and 4.59 g m^?2, respectively. Even larger biomass of 6.26 g m^?2 is estimated if one chooses to use in the calculations the greatest from the daily values of the estimates listed above at each pixel of the satellite data. Comparisons of POC biomass with primary productivity allowed us to assess temporal and spatial patterns of POC losses.     

A high-shear, low Reynolds number microfluidic rheometer

We present a microfluidic rheometer that uses in situ pressure sensors to measure the viscosity of liquids at low Reynolds number. Viscosity is measured in a long, straight channel using a PDMS-based microfluidic device that consists of a channel layer and a sensing membrane integrated with an array of piezoresistive pressure sensors via plasma surface treatment. The micro-pressure sensor is fabricated using conductive particles/PDMS composites. The sensing membrane maps pressure differences at various locations within the channel in order to measure the fluid shear stress in situ at a prescribed shear rate to estimate the fluid viscosity. We find that the device is capable to measure the viscosity of both Newtonian and non-Newtonian fluids for shear rates up to 10⁴ s^?1 while keeping the Reynolds number well below 1.     

Evaluation of micromilled metal mold masters for the replication of microchip electrophoresis devices

High-precision micromilling was assessed as a tool for the rapid fabrication of mold masters for replicating microchip devices in thermoplastics. As an example, microchip electrophoresis devices were hot embossed in poly(methylmethacrylate) (PMMA) from brass masters fabricated via micromilling. Specifically, sidewall roughness and milling topology limitations were investigated. Numerical simulations were performed to determine the effects of additional volumes present on injection plugs (i.e., shape, size, concentration profiles) due to curvature of the corners produced by micromilling. Elongation of the plug was not dramatic (< 20%) for injection crosses with radii of curvatures to channel width ratios less than 0.5. Use of stronger pinching potentials, as compared to sharp-corner injectors, were necessary in order to obtain short sample plugs. The sidewalls of the polymer microstructures were characterized by a maximum average roughness of 115 nm and mean peak height of 290 nm. Sidewall roughness had insignificant effects on the bulk EOF as it was statistically the same for PMMA microchannels with different aspect ratios compared to LiGA-prepared devices with a value of ca. 3.7 × 10⁻⁴ cm²/(V s). PMMA microchip electrophoresis devices were used for the separation of pUC19 Sau3AI double-stranded DNA. The plate numbers achieved in the micromilled-based chips exceeded 1 million/m and were comparable to the plate numbers obtained for the LiGA-prepared devices of similar geometry.     

Upper ocean response to Super Typhoon Tembin (2012) explored using multiplatform satellites and Argo float observations

Using multiplatform satellites and in situ Argo float observations, this study systematically examined the upper ocean response to Super Typhoon Tembin (2012) in the western north pacific, and the interaction between typhoon and a pre-existing cold core eddy (CCE) was particularly focused on. Significant sea surface temperature (SST) cooling and sea surface height anomaly (SSHA) decrease was detected along track after typhoon, with the maximum SST cooling and SSHA decrease reaching 4.0°C and 25 cm, respectively. The pre-existing CCE was located to the left of the typhoon track, resulting in an intriguing leftward bias of SST cooling. The maximum SST cooling appeared at about 25 km to the left of the typhoon track, with SST cooling to the left of the track 40–100% larger than that to the right. After typhoon, the CCE was expanded by 50% due to the typhoon’s cyclonic wind stress. The thermocline was uplifted by 15–25 m by the typhoon-induced upwelling. Typhoon-enhanced vertical mixing was inferred from high-resolution Argo float data based on the Gregg–Henyey–Polzin parameterization method. The diapycnal diffusivity reached 9 × 10^?4 m² s^?1 after typhoon, which was more than 10 times larger than that before typhoon.     

Glacier elevation changes (2012–2016) of the Puruogangri Ice Field on the Tibetan Plateau derived from bi-temporal TanDEM-X InSAR data

This study aims to evaluate the potential of TerraSAR-X (TSX) add-on for Digital Elevation Measurement (TanDEM-X) bi-static synthetic aperture radar (SAR) data sets for the retrieval of glacier digital elevation models (DEMs) and elevation changes over mountain regions. We exploited two pairs of TanDEM-X SAR data sets acquired in 2012 and 2016 over the Puruogangri Ice Field (PIF), which is the largest modern glacier on the Tibetan Plateau (TP). Two fine-detail and high-precision DEMs for 2012 and 2016 over the PIF were generated by differential interferometric processing, and were validated against height measurements from global positioning system (GPS) and Ice, Cloud, and land Elevation Satellite (ICESat) altimetry, yielding a vertical accuracy of 1.91 ± 0.76 m and 1.69 ± 0.83 m, respectively. The elevation changes were derived by differencing the bi-temporal TanDEM-X DEMs and revealed predominant glacier surface thinning on the PIF. An annual surface thinning rate of ?0.317 ± 0.027 m year^?1 was estimated in the period 2012–2016, which is much larger than the estimate of ?0.049 ± 0.200 m year^?1 for the period 2000–2012 reported in previous studies. This accelerating trend of glacier surface thinning might be attributable to the continued increase in summer temperature since the 1980s and decrease in annual precipitation between two periods of investigation. This study demonstrates that comparison of the bi-temporal TanDEM-X DEMs is an efficient method for accurate and detailed retrieval of the latest surface elevation changes of mountain glaciers.     

Enhanced sample concentration on a three-dimensional origami paper-based analytical device with non-uniform assay channel

Traditional microfluidic paper-based analytical devices (μPADs) consist of a flat straight channel printed on a paper substrate. Such devices provide a promising low-cost solution for a variety of biomedical assays. However, they have a relatively high sample consumption due to their use of external reservoirs. Moreover, in μPADs based on the ion concentration polarization (ICP) effect, controlling the cross-sectional area of the Nafion membrane relative to that of the hydrophilic channel is difficult. Accordingly, the present study utilizes an origami technique to create a μPAD with a three-dimensional (3D) structure. The μPAD features short channels and embedded reservoirs, and therefore reduces both the driving voltage requirement and the sample consumption. Moreover, the preconcentration effect is enhanced through the use of an additional hydrophilic area adjacent to the Nafion membrane. The existence of electroosmotic flow (EOF) within the proposed device is confirmed using a current-monitoring method. In addition, the occurrence of ICP is evaluated by measuring the current–voltage response of the device at external voltages ranging from 0 to 50 V. The experimental results obtained for a fluorescein sample with an initial concentration of 10^?5 M show that a 100-fold enhancement factor can be achieved given the use of a non-uniform-geometry design for the assay channel and an additional hydrophilic region with an area equal to approximately 10% of the channel cross-sectional area. Finally, a 100-fold factor can also be achieved for a fluorescein isothiocyanate sample with an initial concentration of 10^?6 M given an external driving voltage of 40 V.     

Selective and in-situ determination of carbonate and oxide particles in aqueous solution using laser-induced breakdown spectroscopy (LIBS) for wearable information equipment

Laser-induced breakdown spectroscopy (LIBS) has been applied for quantitative analysis of Al₂O₃, CaCO₃ and MgO particles suspended in water. In the single elemental system, the plasma emission intensities of Al, Ca and Mg were linearly increased with concentration of elements in the range of 1.0×10^?5–1.0×10^?3  M, 1.0×10^?4–2.0×10^?3 M and 8.0×10^?5 –4.0×10^?3 M, respectively. We also investigated the concentration dependence of breakdown spectra for suspended mixtures of Al₂O₃, CaCO₃ and MgO particles. The emission lines, such as Al I, Ca I, Ca II and Mg I, were appeared in the LIBS spectrum simultaneously, and each emission peak could be deconvoluted. The plasma emission intensities of Al, Ca and Mg in the multielemental system were also linearly increased with their concentrations in the range of 1.0×10^?5–1.0×10^?3 M, 1.0×10^?4–2.0×10^?3 M and 4.0×10^?4–2.0×10^?3 M, respectively. LIBS was found to be available for quantitative and qualitative measurement of the concentrations of Al₂O₃, CaCO₃ and MgO particles suspended in water. The present results suggest that LIBS is a potentially useful tool for in-situ analysis on particles composition and concentrations for environmental monitoring by the wearable information equipments.     

Dielectrophoresis measurement of bovine endothelial cells adhesion on different materials

In this study, the design, fabrication, and characterization of dielectrophoresis based devices for the measurement of bovine endothelial cell adhesion on different biomaterials are conducted. During the design stage, the finite element analysis software COMSOL is used to determine a better design for the dielectrophoretic electrode. Accordingly, a dielectrophoretic device that contains several micro electrodes for producing unbalanced electrical fields is fabricated using the microelectromechanical fabrication technique. The proposed device is then used for the detection of cell adhesion on polydimethylsiloxane (PDMS) and poly lactide (PLA) substrates. The hydrophilicity measurement results reveal that PLA is more hydrophilic than PDMS. It is inferred that bovine endothelial cell (BEC) should have better adhesion on PLA than on PDMA. However, the cell detachment results do not fully agree with this inference. It is further suggested that other features of the substrate are more crucial for the adhesion of BEC than the hydrophilicity. Cell detachment experiments demonstrate that the applied electrophoresis cannot detach the adhered BECs from a PDMS substrate when the seeding time is longer than 4 h. However, the dielectrophoretic force caused by a 6 V applied potential is enough to lift those cells cultured on the PLA for 4 and 6 h respectively. When the culture time is increased to 8 h, the cells apparently stretch out and a higher voltage is required to lift and move them. The results of the cell detachment experiments may suggest that the adherence of BEC to PLA is more stable after 8 h of seeding.     

Development and characterization of a microthermoelectric generator with plated copper/constantan thermocouples

This work reports the development and the characterization of a microthermoelectric generator (μTEG) based on planar technology using electrochemically deposited constantan and copper thermocouples on a micro machined silicon substrate with a SiO₂/Si₃N₄/SiO₂ thermally insulating membrane to create a thermal gradient. The μTEG has been designed and optimized by finite element simulation in order to exploit the different thermal conductivity of silicon and membrane in order to obtain the maximum temperature difference on the planar surface between the hot and cold junctions of the thermocouples. The temperature difference was dependent on the nitrogen (N₂) flow velocity applied to the upper part of the device. The fabricated thermoelectric generator presented maximum output voltage and power of 118 mV/cm² and of 1.1 μW/cm², respectively, for a device with 180 thermocouples, 3 kΩ of internal resistance, and under a N₂ flow velocity of 6 m/s. The maximum efficiency (performance) was 2 × 10^?3 μW/cm² K².     

Design and fabrication of an electrochemically actuated microvalve

A microfluidic valve based on electrochemical (ECM) actuation was designed, fabricated using UV-LIGA microfabrication technologies. The valve consists of an ECM actuator, polydimethylsiloxane (PDMS) membrane and a micro chamber. The flow channels and chamber are made of cured SU-8 polymer. The hydrogen gas bubbles were generated in the valve microchamber with Pt black electrodes (coated with platinum nanoparticles) and filled with 1 M of NaCl solution. The nano particles coated on the working electrode helps to boost the surface-to-volume ratio of the electrode for faster reversible electrolysis and faster valve operation. To test the functionality of the microvalve, a simple micropump based on ECM principle was also integrated in the system to deliver a microscopic volume of fluid through the valve. The experimental results have showed that an approximately 300 μm deflection of valve membrane was achieved by applying a bias voltage of ?1.5 V across the electrodes. The pressure in the valve chamber was estimated to be about 200 KPa. Experimental results proved that the valve can be easily operated by controlling the electrical signals supplied to the ECM actuators.     

A silicone-based microfluidic chip grafted with carboxyl functionalized hyperbranched polyglycerols for selective protein capture

A poly(dimethylsiloxane) (PDMS)-based functional microfluidic device containing a charged matrix of PDMS pillar arrays grafted with hyperbranched polyglycerols (HPGs) was developed. Samples of PDMS were modified with allylamine plasma to form amine groups on the surface prior to the covalent grafting of succinimdyl ester-functionalized HPGs. The anionic functionality of the PDMS channel matrices was developed by altering the number of carboxyl groups present on the HPGs. The grafting of HPGs onto PDMS plates was investigated via contact angle measurement and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), while the grafting of the inside channel was investigated by electroosmotic flow (EOF) measurements. The charge density on grafted HPG was optimized to minimize the nonspecific protein adsorption and increase the selective capture of positively charged proteins. A proof-of-concept device was fabricated on PDMS and demonstrated that the device selectively captures positively charged protein (avidin) from a mixture of bovine serum albumin (BSA)-avidin at pH 7.4 in phosphate buffered saline (PBS). In order to increase the capture efficiency of the proteins in this PDMS-based device, pillar arrays have been fabricated within the channel. As a demonstration, the new device separated two proteins with an avidin capture efficiency of 100 ± 2.95% per 3 min from a 0.02 mg/ml protein solution (avidin:BSA wt ratio: 1:1). This new microfluidic-based device shows a great deal of promise as a tool for protein capture and analysis.