This work was supported by National Research Foundation of Korea (NRF) grants (2013R1A2A2A05004314, 2012R1A1A2043747), a grant from the Korean Health Technology R&#38;D Project, Ministry of Health &#38; Welfare (A121994) and IBS-R020-D1 funded by the Korean Government.

NOTE: Blood was drawn from healthy individuals and was collected in a blood collection tube. Written informed consent was obtained from all volunteers.
1. Fabrication of TiO2 NF Mat
<ol>
	<li>Preparation of precursor solution22
	<ol>
		<li>Dissolve 1.5 g of titanium tetraisopropoxide (TTIP) in a mixture of ethanol (99.9%, 3 ml) and glacial acetic acid (3 ml) and mix the solution at RT (25 &#176;C) for 30 min on a magnetic stirrer.</li>
		<li>Dissolve 11 wt% of polyvinyl pyrrolidone (PVP) in 3.64 g of ethanol (99.9%) and stir the solution at 65 &#176;C for 1 hr using a hot-plate magnetic stirrer.</li>
		<li>Combine and stir the two solutions at 65 &#176;C for 4 hr on a hot-plate magnetic stirrer.</li>
	</ol>
	</li>
	<li>Electrospinning
	<ol>
		<li>Load the prepared solution into a syringe connected to a stainless steel needle of 200 &#956;m inner diameter. Pour the solution directly into the syringe after removing the plunger.</li>
		<li>Introduce the solution constantly at a flow rate of 0.3 ml/hr for 10 min onto a Si wafer (2 cm x 2 cm) placed on a grounded substrate at a high DC voltage (15 kV). During the electrospinning, set the distance between the needle and the grounded substrate to 10 cm.</li>
	</ol>
	</li>
	<li>Calcination of the NF mat
	<ol>
		<li>Place the NF mat in a furnace and increase the temperature up to 500 &#176;C with a ramping rate of 3 &#176;C/min under high-vacuum condition (5 x 10-5 torr).</li>
		<li>Maintain the temperature at 500 &#176;C for 3 hr. Cool down the temperature of the samples to the RT (25 &#176;C) in the furnace.</li>
	</ol>
	</li>
</ol>
2. Integration of TiO2 NF Mat into a Centrifugal Microfluidic Disc
<ol>
	<li>Fabrication of a disc
	<ol>
		<li>Use the 3D designing software (e.g., SolidWorks or similar) to depict chambers, channels, or valves of each layer of disc. Convert the design files to computer numerical control (CNC) code using code generating software (e.g., Edgecam or similar). Use the softwares according to the instruction manual.23,24 Note: The typical channel dimensions used in this device are 1.0 mm x 0.3 mm (width x depth).</li>
		<li>Open the operating software of CNC milling machine (e.g., DeskCNC or similar) and load CNC code to the operating software and click the following in order: &#34;AUTO&#34; -&#62; &#34;G CODE OPEN&#34; -&#62; Select the generated CNC code.</li>
		<li>Attach the PC plate on the CNC milling machine: use 1 mm PC plates for the top layer and 5 mm PC plates for the disc layer. Run the CNC milling machine to cut each layer of the disc by clicking the &#34;START&#34; button.</li>
	</ol>
	</li>
	<li>Transfer of TiO2 NF mat onto the disc
	<ol>
		<li>Place a silicon substrate and a small petri dish containing 40 &#181;L of (tridecafluoro-1,1,2,2-tetrahydrooctyl)-1-trichlorosilane in a vacuum chamber under vacuum for 30 min. The fluorosilane vaporizes and gets coated on the substrate.</li>
		<li>Mix polydimethylsiloxane (PDMS) pre-polymer with a curing agent in a 10:1 ratio and degas in a vacuum chamber. Spin-coat the PDMS onto a silicon substrate at 650 rpm for 60 sec.</li>
		<li>Cure the PDMS coated on silicon substrate in an oven at 65 &#176;C for 10 min to achieve an adherent state. 
		NOTE: Curing time can be varied depending on environmental conditions, and adhesion force can be tested by a tack test using a rheometer.</li>
		<li>Transfer the TiO2 NF mat prepared by electrospinning and calcination onto the PDMS-coated silicon using a tweezer. Then, manually apply a conformal pressure on the transferred TiO2 NF mat with a flat object (e.g., glass slide) and remove the object. Put this sample in the oven at 65 &#176;C for 4 hr or at 80 &#176;C for 1 hr to cure the PDMS layer completely.</li>
		<li>Coat binding reaction chambers in the disc with 20 &#181;l&#160;the PDMS/curing agent mixture (10:1), which acts as an adhesive layer to attach TiO2 NF mat onto the disc.</li>
		<li>Dispense 50 &#181;l of ethanol (99.9%) on the TiO2 NF mat on the PDMS layer, cut the NF mat with a punch hole of 6 mm diameter, and transfer the cut TiO2 NF mat to the binding reaction chambers coated with 20 &#181;l of the PDMS in the previous step. 
		NOTE: In this step, ethanol will be helpful to detach the cut TiO2 NF mat from the Si substrate.</li>
		<li>Incubate the TiO2 NF mat integrated disc in the oven at 65 &#176;C for 4 hr or at 80 &#176;C for 1 hr to cure the PDMS completely.</li>
	</ol>
	</li>
	<li>Surface modification of the TiO2 NF mat on the disc 
	<ol>
		<li>Prepare 1% v/v solution of (3-glycidoxypropyl)methyldiethoxy silane (GPDES) in ethanol (99.9%).</li>
		<li>Treat the TiO2 NF mat integrated disc with oxygen plasma at 140 W, 50 sccm oxygen flow for 180 sec. Dispense 100 &#956;l of GPDES solution on each nanofiber mat and incubate at RT (25 &#176;C) for 2 hr.</li>
		<li>Wash the substrates briefly by dispensing ethanol (99.9%) using a wash bottle, then remove the ethanol completely by inverting the disc and blotting it against a clean wipe. Cure at 80 &#176;C for 1 hr. Wash twice with ethanol (99.9%) in the same manner as stated above, to remove the physically adsorbed and unbound GPDES molecules.</li>
		<li>Blow dry with a nitrogen stream, dry under vacuum. 
		NOTE: The disc can be stored in a sealed container at RT (25 &#176;C) until use.</li>
	</ol>
	</li>
	<li>Immobilization of antibodies on the surface
	<ol>
		<li>Make a solution of 200 &#956;g/ml of capture antibodies (monoclonal mouse antihuman hsCRP or monoclonal mouse anti-cTnI) by diluting the antibodies with a phosphate buffered saline (PBS) buffer (pH 7.4). Dispense 5 &#956;l of the solution onto each NF mat in a disc using a micropipette. See materials list for more information about the antibodies.</li>
		<li>Keep the discs in a humidified chamber and incubate at 37 &#176;C for 4 hr. Wash the antibodies&#160;coated NF mat with 0.1% BSA-PBS buffer. Fill the chamber with 100 &#956;l of wash buffer using a micropipette, remove the buffer by aspirating or decanting. Finally, invert the disc and blot it against a clean wipe, and then assemble the disc.</li>
	</ol>
	</li>
	<li>Disc assembly
	<ol>
		<li>Draw the design of the disc on double-side adhesive tape using a CAD program (e.g., AutoCAD or similar). Load the CAD design to the cutting plotter.</li>
		<li>Cut the double-side adhesive tape using the cutting plotter. Peel off one protection layer of double adhesive tape and attach it on top of the disc layer. Peel off the other protection layer and attach the top layer on the disc layer.</li>
		<li>Load the preliminarily assembled disc in the pressing machine and precisely align top/adhesive/disc layers using align marks in each layer to connect each valve, channel, and chambers. Apply conformal pressure using the pressing machine.</li>
	</ol>
	</li>
</ol>
3. Immunoassay
<ol>
	<li>Fill the chambers with 1% BSA-PBS buffer using a micropipette and incubate the disc at 37 &#176;C for 1 hr. Remove the buffer by aspiration using a micropipette. Perform this step to block the un-reacted sites and to reduce non-specific adsorption of protein in a disc.</li>
	<li>Wash twice with 0.1% BSA-PBS by filling and aspirating the chambers using a micropipette. 
	NOTE: At this stage the disc can be stored at 4 &#176;C until use.</li>
	<li>Load 10 &#956;l of antigen-spiked whole blood or CRP-free serum for CRP detection on the disc using a micropipette. For making the calibration graphs, use concentrations of CRP from 1 pg/ml to 100 ng/ml; and cTnI from 10 pg/ml to 100 ng/ml. 
	NOTE: Due to the higher levels of CRP in whole blood, which is usually in &#181;M range, CRP-free serum was used to demonstrate the low detection limit of the device.</li>
	<li>Spin the disc at 3,600 rpm (391 x g) for 60 sec to separate the red blood cells.</li>
	<li>Open valve #1 by laser irradiation, and transfer 4 &#956;l of the supernatant plasma to the chamber containing 8 &#956;l of detecting antibodies conjugated with HRP by spinning the disc at 2,400 rpm for 3 sec. 
	NOTE: The general processes for valve actuation and visualization of disc operation are described in detail in a previous report.21</li>
	<li>Apply a mixing mode (15 Hz s-1, 15&#176;) for 5 sec for binding of the protein and detection antibodies.</li>
	<li>Open valve #2, and transfer the mixture prepared in step 6 to the binding reaction chamber (2,400 rpm, 3 sec). Then, apply a mixing mode (60 Hz s-1, 2&#176;) for 20 min to achieve an immunoreaction between the mixture and the binding antibodies on the TiO2 NFs. After the reaction, open valve #3 and transfer the residual mixture to the waste chamber (2,400 rpm, 10 sec).</li>
	<li>Transfer the washing buffer (600 &#181;l) to the binding reaction chamber by opening valve #4 and spinning the disc (2,400 rpm, 4 sec). Then apply a mixing mode (30 Hz s-1, 30&#176;) for 120 sec to wash the TiO2 NFs in the chamber.</li>
	<li>Wash the TiO2 NFs twice more by following same condition of step 3.8, and remove the residual washing buffer completely by spinning the disc at 2,400 rpm for 20 sec. Then, close the valve #5.</li>
	<li>For the chemiluminescent reaction, apply a mixing mode (30 Hz s-1, 2&#176;) for 1 min after transferring the chemiluminescent substrate solution to the binding reaction chamber by opening valve #6 and spinning the disc at 2,400 rpm for 10 sec subsequently.</li>
	<li>Transfer the reacted substrate solution to the detection chambers&#160;by opening valve #7 and spinning the disc at 2,400 rpm for 10 sec.</li>
	<li>Measure chemiluminescence signals from the reacted substrate solution using a photomultiplier tube (PMT) module equipped detection system. &#160; 
	NOTE: The detection system is a custom-built machine using the following parts: step motor, optomechanical components, translation stages, and commercially available PMT. The optomechanical parts and step motor are assembled to hold the device, and the motor can rotate the disc. The detection is performed by PMT fixed on the optomechanical parts, and it is located above the detection chambers of the device. By manipulating the step motor, the detection chambers are aligned right below the detection zone of PMT.</li>
</ol>

<ol>
	<li>Zhang, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanomaterials+for+Ultrasensitive+Protein+Detection.">Nanomaterials for Ultrasensitive Protein Detection.</a> Adv. Mater. 25 (28), 3802-3819 (2013).</li><li>Hu, W., Li, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanomaterial-based+advanced+immunoassays.">Nanomaterial-based advanced immunoassays.</a> Wiley Interdiscip. Rev. Nanomed. Nanobiotechnol. 3 (2), 119-133 (2011).</li><li>Yang-Kyu, C., Chang-Hoon, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Silicon+Nanowire+Biosensor+for+Cancer+Markers.">Silicon Nanowire Biosensor for Cancer Markers.</a> Biosensors and Cancer. , 164-183 (2012).</li><li>Baltazar, R., Vistas, C. R., Ferreira, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biosensing+Applications+Using+Nanoparticles.">Biosensing Applications Using Nanoparticles.</a> Nanocomposite Particles for Bio-Applications. , 265-282 (2011).</li><li>Roy, P., Berger, S., Schmuki, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TiO2+Nanotubes:+Synthesis+and+Applications.">TiO2 Nanotubes: Synthesis and Applications.</a> Angew. Chem. Int. Ed. 50 (13), 2904-2939 (2011).</li><li>Yang, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospun+Nanofibrous+Membranes:+A+Novel+Solid+Substrate+for+Microfluidic+Immunoassays+for+HIV.">Electrospun Nanofibrous Membranes: A Novel Solid Substrate for Microfluidic Immunoassays for HIV.</a> Adv. Mater. 20 (24), 4770-4775 (2008).</li><li>Chantasirichot, S., Ishihara, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospun+phospholipid+polymer+substrate+for+enhanced+performance+in+immunoassay+system.">Electrospun phospholipid polymer substrate for enhanced performance in immunoassay system.</a> Biosens. Bioelectron. 38 (1), 209-214 (2012).</li><li>Zhang, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospun+TiO2+Nanofiber-Based+Cell+Capture+Assay+for+Detecting+Circulating+Tumor+Cells+from+Colorectal+and+Gastric+Cancer+Patients.">Electrospun TiO2 Nanofiber-Based Cell Capture Assay for Detecting Circulating Tumor Cells from Colorectal and Gastric Cancer Patients.</a> Adv. Mater. 24 (20), 2756-2760 (2012).</li><li>Ali, M. A., Mondal, K., Singh, C., Dhar Malhotra, B., Sharma, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anti-epidermal+growth+factor+receptor+conjugated+mesoporous+zinc+oxide+nanofibers+for+breast+cancer+diagnostics.">Anti-epidermal growth factor receptor conjugated mesoporous zinc oxide nanofibers for breast cancer diagnostics.</a> Nanoscale. 7 (16), 7234-7245 (2015).</li><li>Mondal, K., Ali, M. A., Agrawal, V. V., Malhotra, B. D., Sharma, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Highly+Sensitive+Biofunctionalized+Mesoporous+Electrospun+TiO2+Nanofiber+Based+Interface+for+Biosensing.">Highly Sensitive Biofunctionalized Mesoporous Electrospun TiO2 Nanofiber Based Interface for Biosensing.</a> ACS Appl. Mater. Interfaces. 6 (4), 2516-2527 (2014).</li><li>Tu, W., Dong, Y., Lei, J., Ju, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low-Potential+Photoelectrochemical+Biosensing+Using+Porphyrin-Functionalized+TiO2+Nanoparticles.">Low-Potential Photoelectrochemical Biosensing Using Porphyrin-Functionalized TiO2 Nanoparticles.</a> Anal. Chem. 82 (20), 8711-8716 (2010).</li><li>Liu, S., Chen, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coadsorption+of+Horseradish+Peroxidase+with+Thionine+on+TiO2+Nanotubes+for+Biosensing.">Coadsorption of Horseradish Peroxidase with Thionine on TiO2 Nanotubes for Biosensing.</a> Langmuir. 21 (18), 8409-8413 (2005).</li><li>Portan, D. V., Kroustalli, A. A., Deligianni, D. D., Papanicolaou, G. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=On+the+biocompatibility+between+TiO2+nanotubes+layer+and+human+osteoblasts.">On the biocompatibility between TiO2 nanotubes layer and human osteoblasts.</a> J.Biomed.Mater.Res. Part A. 100 (10), 2546-2553 (2012).</li><li>Dettin, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Covalent+surface+modification+of+titanium+oxide+with+different+adhesive+peptides:+Surface+characterization+and+osteoblast-like+cell+adhesion.">Covalent surface modification of titanium oxide with different adhesive peptides: Surface characterization and osteoblast-like cell adhesion.</a> J. Biomed. Mater. Res. Part A. 90 (1), 35-45 (2009).</li><li>Kim, W. -. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+Protein+Immobilization+Efficiency+on+a+TiO2+Surface+Modified+with+a+Hydroxyl+Functional+Group.">Enhanced Protein Immobilization Efficiency on a TiO2 Surface Modified with a Hydroxyl Functional Group.</a> Langmuir. 25 (19), 11692-11697 (2009).</li><li>Son, K. J., Ahn, S. H., Kim, J. H., Koh, W. -. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Graft+Copolymer-Templated+Mesoporous+TiO2+Films+Micropatterned+with+Poly(ethylene+glycol)+Hydrogel:+Novel+Platform+for+Highly+Sensitive+Protein+Microarrays.">Graft Copolymer-Templated Mesoporous TiO2 Films Micropatterned with Poly(ethylene glycol) Hydrogel: Novel Platform for Highly Sensitive Protein Microarrays.</a> ACS Appl. Mater. Interfaces. 3 (2), 573-581 (2011).</li><li>Kar, P., Pandey, A., Greer, J. J., Shankar, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrahigh+sensitivity+assays+for+human+cardiac+troponin+I+using+TiO2+nanotube+arrays.">Ultrahigh sensitivity assays for human cardiac troponin I using TiO2 nanotube arrays.</a> Lab Chip. 12 (4), 821-828 (2012).</li><li>Agarwal, S., Wendorff, J. H., Greiner, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+electrospinning+technique+for+biomedical+applications.">Use of electrospinning technique for biomedical applications.</a> Polymer. 49 (26), 5603-5621 (2008).</li><li>Ding, B., Wang, M., Wang, X., Yu, J., Sun, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospun+nanomaterials+for+ultrasensitive+sensors.">Electrospun nanomaterials for ultrasensitive sensors.</a> Mater. Today. 13 (11), 16-27 (2010).</li><li>Liu, Y., Yang, D., Yu, T., Jiang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Incorporation+of+electrospun+nanofibrous+PVDF+membranes+into+a+microfluidic+chip+assembled+by+PDMS+and+scotch+tape+for+immunoassays.">Incorporation of electrospun nanofibrous PVDF membranes into a microfluidic chip assembled by PDMS and scotch tape for immunoassays.</a> ELECTROPHORESIS. 30 (18), 3269-3275 (2009).</li><li>Lee, W. S., Sunkara, V., Han, J. -. R., Park, Y. -. S., Cho, Y. -. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospun+TiO2+nanofiber+integrated+lab-on-a-disc+for+ultrasensitive+protein+detection+from+whole+blood.">Electrospun TiO2 nanofiber integrated lab-on-a-disc for ultrasensitive protein detection from whole blood.</a> Lab Chip. 15 (2), 478-485 (2015).</li><li>Li, D., Xia, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+of+Titania+Nanofibers+by+Electrospinning.">Fabrication of Titania Nanofibers by Electrospinning.</a> Nano Lett. 3 (4), 555-560 (2003).</li><li>Lombard, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> SolidWorks 2013 BIBLE. , (2013).</li><li>Tickoo, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> EdgeCAM 11.0 for Manufacturers. , (2007).</li><li>Zhu, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+adhesion+of+interconnected+TiO2+nanofiber+network+on+conductive+substrate+and+its+application+in+polymer+photovoltaic+devices.">Improved adhesion of interconnected TiO2 nanofiber network on conductive substrate and its application in polymer photovoltaic devices.</a> Appl. Phys. Lett. 93 (1), 013102 (2008).</li><li>Song, M. Y., Ahn, Y. R., Jo, S. M., Kim, D. Y., Ahn, J. -. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TiO2+single-crystalline+nanorod+electrode+for+quasi-solid-state+dye-sensitized+solar+cells.">TiO2 single-crystalline nanorod electrode for quasi-solid-state dye-sensitized solar cells.</a> Appl. Phys. Lett. 87 (11), 113113 (2005).</li><li>Katsuhiro, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospinning+processed+nanofibrous+TiO2+membranes+for+photovoltaic+applications.">Electrospinning processed nanofibrous TiO2 membranes for photovoltaic applications.</a> Nanotechnology. 17 (4), 1026-1031 (2006).</li></ol>

The authors have nothing to disclose.

The assay on TiO2 NF integrated disc is a rapid, inexpensive and convenient technique for the ultrasensitive detection of low abundant proteins present in very low volume of blood. This technique has the advantage of using small sample volumes (10 &#956;l) and is amenable for analysis of multiple samples simultaneously. This provides a great potential as a multiplexing immunoassay device. The device has the added advantage that it does not require sample pretreatment steps like plasma separation, which are req...

Several platforms for disease diagnosis have been developed based on nanoscale materials1,2 such as nanowires,3 nanoparticles,4 nanotubes,5 and nanofibers (NFs)6-8. These nanomaterials offer excellent prospects in the design of new technologies for highly sensitive bioassays owing to their unique physicochemical properties. For example, mesoporous zinc oxide nanofibers have been used for the femto-molar sensitive detection of breast cancer biomarkers.9 Recently, nanomaterials based on titanium dioxide (TiO2) have been explored for bioanalytical applications10 considering their chemical stability,11 negligible protein denaturation,12 and biocompatibility.13 In addition, the hydroxyl groups on the surface of TiO2 facilitate chemical modification and the covalent attachment of biomolecules.14,15 Patterned TiO2 thin films16 or TiO2 nanotubes17 have been utilized to enhance the detection sensitivity of a target protein by increasing the surface area; however, the fabrication process is rather complex and requires expensive equipment. On the other hand, electrospun NFs are receiving attention because of their high surface area as well as straightforward and low-cost fabrication process;18,19 yet, the fragile or loose characteristic of the electrospun TiO2 NF mat makes it difficult to handle and integrate with microfluidic devices.6,20 Therefore, the TiO2 NF mats were rarely utilized in bioanalytical applications, particularly those requiring harsh washing conditions.
In this study, to overcome these limitations, we have developed a new technology for transferring the electrospun NF mats onto the surface of any target substrate by utilizing a thin polydimethylsiloxane (PDMS) adhesive layer. Furthermore, we have successfully showed the integration of electrospun TiO2 NF mats onto a centrifugal microfluidic device made of polycarbonate (PC). Using this device, a high-sensitive, fully automated, and integrated detection of C-reactive protein (CRP) as well as cardiac troponin I (cTnI) was achieved within 30 min from only 10 &#956;L of whole blood.21 Due to the combined advantages of the properties of the NFs and the centrifugal platform, the assay exhibited a wide dynamic range of six orders of magnitude from 1 pg/ml (~8 fM) to 100 ng/ml (~0.8 pM) with a lower limit of detection of 0.8 pg/ml (~6 fM) for CRP and a dynamic range from 10 pg/ml (~0.4 pM) to 100 ng/ml (~4 nM) with a detection limit of 37 pg/ml (~1.5 pM) for cTnI. These detection limits are ~300 and ~20-fold lower compared to their corresponding conventional ELISA results. This technique could be applied for the detection of any target proteins, with appropriate antibodies. Overall, this device could contribute greatly to in-vitro diagnostics and biochemical assays since it can detect rare amounts of target proteins with great sensitivity even from very small quantities of biological samples; e.g., 10 &#956;l&#160;of whole blood. Though we only demonstrated the serum protein detection using ELISA in this study, the transfer and integration technology of electrospun NFs with microfluidic devices could be more broadly applied in other biochemical reactions which require a large surface area for high detection sensitivity.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Si wafer</td>
			<td>LG SILTRON</td>
			<td>Polished Wafer, test grade</td>
			<td>Dia. (mm) = 150, orientation = &#60;100&#62;, dopant = boron, RES(Ohm-cm) = 1 - 30, thickness (&#956;m) = 650 - 700</td>
		</tr>
		<tr>
			<td>Polycarbonate (PC)&#160;</td>
			<td>Daedong Plastic</td>
			<td>PCS#6900</td>
			<td>Thickness (mm) = 1 and 5&#160;</td>
		</tr>
		<tr>
			<td>Titanium tetraisopropoxide, 98%,</td>
			<td>Sigma-Aldrich</td>
			<td>205273</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyvinylpyrrolidone, Mw = 1,300,000</td>
			<td>Sigma-Aldrich</td>
			<td>437190</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetic acid</td>
			<td>Sigma-Aldrich</td>
			<td>320099</td>
			<td></td>
		</tr>
		<tr>
			<td>Anhydrous ethanol</td>
			<td>Sigma-Aldrich</td>
			<td>459836</td>
			<td></td>
		</tr>
		<tr>
			<td>Tridecafluoro-1,1,2,2-tetrahydrooctyl)-1-trichlorosilane</td>
			<td>Sigma-Aldrich</td>
			<td>448931</td>
			<td></td>
		</tr>
		<tr>
			<td>PDMS and curing agent</td>
			<td>Dow Corning</td>
			<td>SYLGARD 184</td>
			<td></td>
		</tr>
		<tr>
			<td>GPDES</td>
			<td>Gelest Inc</td>
			<td>SIG5832.0&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>J T Baker</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>FE-SEM</td>
			<td>FEI</td>
			<td>Nova NanoSEM</td>
			<td></td>
		</tr>
		<tr>
			<td>X-ray photoelectron spectroscopy</td>
			<td>ThermoFisher</td>
			<td>K-alpha</td>
			<td></td>
		</tr>
		<tr>
			<td>3D modeling machine</td>
			<td>M&#38;I CNC Lab, Korea</td>
			<td></td>
			<td>CNC milling machine</td>
		</tr>
		<tr>
			<td>Wax-dispensing machine</td>
			<td>Hanra Precision Eng. Co. Ltd., Korea</td>
			<td></td>
			<td>Customized</td>
		</tr>
		<tr>
			<td>Double-sided adhesive tape</td>
			<td>FLEXcon, USA</td>
			<td>DFM 200 clear 150 POLY H-9 V-95</td>
			<td></td>
		</tr>
		<tr>
			<td>Cutting plotter</td>
			<td>Graphtec Corporation, Japan</td>
			<td>Graphtec CE3000-60 MK2</td>
			<td></td>
		</tr>
		<tr>
			<td>Spin coater</td>
			<td>MIDAS</td>
			<td>SPIN-3000D</td>
			<td></td>
		</tr>
		<tr>
			<td>Furnace (calcination)</td>
			<td>R. D. WEBB COMPANY</td>
			<td>WEBB 99</td>
			<td></td>
		</tr>
		<tr>
			<td>Rheometer (Tack test)</td>
			<td>Thermo Scientific</td>
			<td>Haake MARS&#160;III - ORM Package</td>
			<td></td>
		</tr>
		<tr>
			<td>Oxygen plasma system</td>
			<td>FEMTO</td>
			<td>CUTE</td>
			<td></td>
		</tr>
		<tr>
			<td>Monoclonal mouse antihuman hsCRP</td>
			<td>Hytest Ltd., Finland</td>
			<td>4C28</td>
			<td>(clone # C5)</td>
		</tr>
		<tr>
			<td>Monoclonal mouse anti-cTnI</td>
			<td>Hytest Ltd., Finland</td>
			<td>4T21</td>
			<td>(clone # 19C7)</td>
		</tr>
		<tr>
			<td>HRP conjugated goat polyclonal anti-hsCRP</td>
			<td>Abcam plc., MA</td>
			<td>ab19175</td>
			<td></td>
		</tr>
		<tr>
			<td>HRP conjugated mouse monoclonal anti-cTnI</td>
			<td>Abcam plc., MA</td>
			<td>ab24460</td>
			<td>(clone # 16A11)</td>
		</tr>
		<tr>
			<td>hsCRP</td>
			<td>Abcam plc., MA</td>
			<td>ab111647</td>
			<td></td>
		</tr>
		<tr>
			<td>cTnI</td>
			<td>Fitzgerald, MA</td>
			<td>30-AT43</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Albumin</td>
			<td>Sigma-Aldrich</td>
			<td>A7906</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Amresco Inc</td>
			<td>E404</td>
			<td></td>
		</tr>
		<tr>
			<td>Blood collection tubes</td>
			<td>BD vacutainer</td>
			<td>367844</td>
			<td>K2 EDTA 7.2 mg plus blood 
			collection tubes</td>
		</tr>
		<tr>
			<td>SuperSignal ELISA femto</td>
			<td>Invitrogen</td>
			<td>37074</td>
			<td></td>
		</tr>
		<tr>
			<td>Modular multilabel plate reader</td>
			<td>Perkin Elmer</td>
			<td>Envision 2104</td>
			<td></td>
		</tr>
		<tr>
			<td>Disc operating machine</td>
			<td>Hanra Precision Eng. Co. Ltd., Korea</td>
			<td></td>
			<td>Customized</td>
		</tr>
		<tr>
			<td>Photomultiplier tube (PMT)</td>
			<td>Hamamatsu Photonics</td>
			<td>H1189-210</td>
			<td></td>
		</tr>
		<tr>
			<td>AutoCAD</td>
			<td>AutoDesk</td>
			<td>Version 2012</td>
			<td>Design software</td>
		</tr>
		<tr>
			<td>SolidWorks 3D CAD software&#160;</td>
			<td>SOLIDWORKS Corp.</td>
			<td>Version 2013</td>
			<td>3D Design software,</td>
		</tr>
		<tr>
			<td>Edgecam</td>
			<td>Vero software</td>
			<td>version 2009.01.06928</td>
			<td>Code generating software</td>
		</tr>
		<tr>
			<td>DeskCNC</td>
			<td>Carken Co.</td>
			<td>version 2.0.2.18</td>
			<td>CNC milling machine software</td>
		</tr>
	</tbody>
</table>

fully automated centrifugal microfluidic device for ultrasensitive protein detection from whole blood

Enzyme-linked immunosorbent assay (ELISA) is a promising method to detect small amount of proteins in biological samples. The devices providing a platform for reduced sample volume and assay time as well as full automation are required for potential use in point-of-care-diagnostics. Recently, we have demonstrated ultrasensitive detection of serum proteins, C-reactive protein (CRP) and cardiac troponin I (cTnI), utilizing a lab-on-a-disc composed of TiO2 nanofibrous (NF) mats. It showed a large dynamic range with femto molar (fM) detection sensitivity, from a small volume of whole blood in 30 min. The device consists of several components for blood separation, metering, mixing, and washing that are automated for improved sensitivity from low sample volumes. Here, in the video demonstration, we show the experimental protocols and know-how for the fabrication of NFs as well as the disc, their integration and the operation in the following order: processes for preparing TiO2 NF mat; transfer-printing of TiO2 NF mat onto the disc; surface modification for immune-reactions, disc assembly and operation; on-disc detection and representative results for immunoassay. Use of this device enables multiplexed analysis with minimal consumption of samples and reagents. Given the advantages, the device should find use in a wide variety of applications, and prove beneficial in facilitating the analysis of low abundant proteins.

Using this protocol, a fully automated centrifugal microfluidic device for protein detection from whole blood with high sensitivity was prepared. The TiO2 NF mats were prepared by processes of electrospinning and calcination. In order to fabricate the NFs of desired diameter, morphology, and thickness, electrospinning conditions such as flow rate, voltage, and spinning time were optimized. When the conditions were not optimized, the quality of the NFs formed was poor. In partic...

Watch this Scientific Journal Video about Fully Automated Centrifugal Microfluidic Device for Ultrasensitive Protein Detection from Whole Blood at JoVE.com

Fully Automated Centrifugal Microfluidic Device for Ultrasensitive Protein Detection from Whole Blood

This protocol demonstrates how to achieve femto molar detection sensitivity of proteins in 10 &#181;L of whole blood within 30 min. This can be achieved by using electrospun nanofibrous mats integrated in a lab-on-a-disc, which offers high surface area as well as effective mixing and washing for enhanced signal-to-noise ratio.

Enzyme-linked immunosorbent assay (ELISA) is a promising method to detect small amount of proteins in biological samples. The devices providing a platform ...

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10.4K Views.  School of Life Sciences, Ulsan National Institute of Science and Technology (UNIST), UNIST-gil 50, Ulsan, Republic of Korea. This protocol demonstrates how to achieve femto molar detection sensitivity of proteins in 10 µL of whole blood within 30 min. This can be achieved by using electrospun nanofibrous mats integrated in a lab-on-a-disc, which offers high surface area as well as effective mixing and washing for enhanced signal-to-noise ratio.

Video: Fully Automated Centrifugal Microfluidic Device for Ultrasensitive Protein Detection from Whole Blood

Microfluidic Device for Recreating a Tumor Microenvironment in Vitro

We have developed a microfluidic device that mimics the delivery and systemic clearance of drugs to heterogeneous three-dimensional tumor tissues in vitro. Nutrients delivered by vasculature fail to reach all parts of tumors, giving rise to heterogeneous microenvironments consisting of viable, quiescent and necrotic cell types. Many cancer drugs fail to effectively penetrate and treat all types of cells because of this heterogeneity. Monolayers of cancer cells do not mimic this heterogeneity, making it difficult to test cancer drugs with a suitable in vitro model. Our microfluidic devices were fabricated out of PDMS using soft lithography. Multicellular tumor spheroids, formed by the hanging drop method, were inserted and constrained into rectangular chambers on the device and maintained with continuous medium perfusion on one side. The rectangular shape of chambers on the device created linear gradients within tissue. Fluorescent stains were used to quantify the variability in apoptosis within tissue. Tumors on the device were treated with the fluorescent chemotherapeutic drug doxorubicin, time-lapse microscopy was used to monitor its diffusion into tissue, and the effective diffusion coefficient was estimated. The hanging drop method allowed quick formation of uniform spheroids from several cancer cell lines. The device enabled growth of spheroids for up to 3 days. Cells in proximity of flowing medium were minimally apoptotic and those far from the channel were more apoptotic, thereby accurately mimicking regions in tumors adjacent to blood vessels. The estimated value of the doxorubicin diffusion coefficient agreed with a previously reported value in human breast cancer. Because the penetration and retention of drugs in solid tumors affects their efficacy, we believe that this device is an important tool in understanding the behavior of drugs, and developing new cancer therapeutics.

Microfluidic Device for Recreating a Tumor Microenvironment in Vitro

We present the procedure for fabrication and operation of a microfluidic device that recreates heterogeneous tumor microenvironments in vitro. The variability in apoptosis within tumor tissue was quantified using fluorescent stains and the effective diffusion coefficient of the chemotherapeutic drug doxorubicin into tumor tissue was evaluated.

We have developed a microfluidic device that mimics the delivery and systemic clearance of drugs to heterogeneous three-dimensional tumor tissues in ...

Fluorescence detection methods for microfluidic droplet platforms

The development of microfluidic platforms for performing chemistry and biology has in large part been driven by a range of potential benefits that accompany system miniaturisation. Advantages include the ability to efficiently process nano- to femoto- liter volumes of sample, facile integration of functional components, an intrinsic predisposition towards large-scale multiplexing, enhanced analytical throughput, improved control and reduced instrumental footprints.1
In recent years much interest has focussed on the development of droplet-based (or segmented flow) microfluidic systems and their potential as platforms in high-throughput experimentation.2-4 Here water-in-oil emulsions are made to spontaneously form in microfluidic channels as a result of capillary instabilities between the two immiscible phases. Importantly, microdroplets of precisely defined volumes and compositions can be generated at frequencies of several kHz. Furthermore, by encapsulating reagents of interest within isolated compartments separated by a continuous immiscible phase, both sample cross-talk and dispersion (diffusion- and Taylor-based) can be eliminated, which leads to minimal cross-contamination and the ability to time analytical processes with great accuracy. Additionally, since there is no contact between the contents of the droplets and the channel walls (which are wetted by the continuous phase) absorption and loss of reagents on the channel walls is prevented.
Once droplets of this kind have been generated and processed, it is necessary to extract the required analytical information. In this respect the detection method of choice should be rapid, provide high-sensitivity and low limits of detection, be applicable to a range of molecular species, be non-destructive and be able to be integrated with microfluidic devices in a facile manner. To address this need we have developed a suite of experimental tools and protocols that enable the extraction of large amounts of photophysical information from small-volume environments, and are applicable to the analysis of a wide range of physical, chemical and biological parameters. Herein two examples of these methods are presented and applied to the detection of single cells and the mapping of mixing processes inside picoliter-volume droplets. We report the entire experimental process including microfluidic chip fabrication, the optical setup and the process of droplet generation and detection.

Droplet-based microfluidic platforms are promising candidates for high throughput experimentation since they are able to generate picoliter, self-compartmentalized vessels inexpensively at kHz rates. Through integration with fast, sensitive and high resolution fluorescence spectroscopic methods, the large amounts of information generated within these systems can be efficiently extracted, harnessed and utilized.

The development of microfluidic platforms for performing chemistry and biology has in large part been driven by a range of potential benefits that ...

Microfluidic Mixers for Studying Protein Folding

The process by which a protein folds into its native conformation is highly relevant to biology and human health yet still poorly understood. One reason for this is that folding takes place over a wide range of timescales, from nanoseconds to seconds or longer, depending on the protein1. Conventional stopped-flow mixers have allowed measurement of folding kinetics starting at about 1 ms. We have recently developed a microfluidic mixer that dilutes denaturant ~100-fold in ~8 &mu;s2. Unlike a stopped-flow mixer, this mixer operates in the laminar flow regime in which turbulence does not occur. The absence of turbulence allows precise numeric simulation of all flows within the mixer with excellent agreement to experiment3-4.
Laminar flow is achieved for Reynolds numbers Re &le;100. For aqueous solutions, this requires micron scale geometries. We use a hard substrate, such as silicon or fused silica, to make channels 5-10 &mu;m wide and 10 &mu;m deep (See Figure 1). The smallest dimensions, at the entrance to the mixing region, are on the order of 1 &mu;m in size. The chip is sealed with a thin glass or fused silica coverslip for optical access. Typical total linear flow rates are ~1 m/s, yielding Re~10, but the protein consumption is only ~0.5 nL/s or 1.8 &mu;L/hr. Protein concentration depends on the detection method: For tryptophan fluorescence the typical concentration is 100 &mu;M (for 1 Trp/protein) and for FRET the typical concentration is ~100 nM.
The folding process is initiated by rapid dilution of denaturant from 6 M to 0.06 M guanidine hydrochloride. The protein in high denaturant flows down a central channel and is met on either side at the mixing region by buffer without denaturant moving ~100 times faster (see Figure 2). This geometry causes rapid constriction of the protein flow into a narrow jet ~100 nm wide. Diffusion of the light denaturant molecules is very rapid, while diffusion of the heavy protein molecules is much slower, diffusing less than 1 &mu;m in 1 ms. The difference in diffusion constant of the denaturant and the protein results in rapid dilution of the denaturant from the protein stream, reducing the effective concentration of the denaturant around the protein. The protein jet flows at a constant rate down the observation channel and fluorescence of the protein during folding can be observed using a scanning confocal microscope5.

In this work we explain the fabrication and use of a microfluidic mixer capable of mixing two solutions in ~8 &mu;s. We also demonstrate the use of these mixers with spectroscopic detection using UV fluorescence and fluorescence resonance energy transfer (FRET).

The process by which a protein folds into its native conformation is highly relevant to biology and human health yet still poorly understood. One reason ...

A Microfluidic Device for Studying Multiple Distinct Strains

The study of cell responses to environmental changes poses many experimental challenges: cells need to be imaged under changing conditions, often in a comparative manner. Multiwell plates are routinely used to compare many different strains or cell lines, but allow limited control over the environment dynamics. Microfluidic devices, on the other hand, allow exquisite dynamic control over the surrounding conditions, but it is challenging to image and distinguish more than a few strains in them. Here we describe a method to easily and rapidly manufacture a microfluidic device capable of applying dynamically changing conditions to multiple distinct yeast strains in one channel. The device is designed and manufactured by simple means without the need for soft lithography. It is composed of a Y-shaped flow channel attached to a second layer harboring microwells. The strains are placed in separate microwells, and imaged under the exact same dynamic conditions. We demonstrate the use of the device for measuring protein localization responses to pulses of nutrient changes in different yeast strains.

We present a simple method to produce microfluidic devices capable of applying similar dynamic conditions to multiple distinct strains, without the need for a clean room or soft lithography.

The study of cell responses to environmental changes poses many experimental challenges: cells need to be imaged under changing conditions, often in a ...

Microfluidic Platform for Measuring Neutrophil Chemotaxis from Unprocessed Whole Blood

Neutrophils play an essential role in protection against infections and their numbers in the blood are frequently measured in the clinic. Higher neutrophil counts in the blood are usually an indicator of ongoing infections, while low neutrophil counts are a warning sign for higher risks for infections. To accomplish their functions, neutrophils also have to be able to move effectively from the blood where they spend most of their life, into tissues, where infections occur. Consequently, any defects in the ability of neutrophils to migrate can increase the risks for infections, even when neutrophils are present in appropriate numbers in the blood. However, measuring neutrophil migration ability in the clinic is a challenging task, which is time consuming, requires large volume of blood, and expert knowledge. To address these limitations, we designed a robust microfluidic assays for neutrophil migration, which requires a single droplet of unprocessed blood, circumvents the need for neutrophil separation, and is easy to quantify on a simple microscope. In this assay, neutrophils migrate directly from the blood droplet, through small channels, towards the source of chemoattractant. To prevent the granular flow of red blood cells through the same channels, we implemented mechanical filters with right angle turns that selectively block the advance of red blood cells. We validated the assay by comparing neutrophil migration from blood droplets collected from finger prick and venous blood. We also compared these whole blood (WB) sources with neutrophil migration from samples of purified neutrophils and found consistent speed and directionality between the three sources. This microfluidic platform will enable the study of human neutrophil migration in the clinic and the research setting to help advance our understanding of neutrophil functions in health and disease.

This protocol details an assay designed to measure human neutrophil chemotaxis from one droplet of whole blood with robust reproducibility. This approach circumvents the need for neutrophil separation and requires only a few minutes of assay preparation time. The microfluidic chip enables the repeated measure of neutrophil chemotaxis over time in infants or small mammals, where sample volume is limited.

Neutrophils play an essential role in protection against infections and their numbers in the blood are frequently measured in the clinic. Higher ...

Protocol for Biofilm Streamer Formation in a Microfluidic Device with Micro-pillars

Several bacterial species possess the ability to attach to surfaces and colonize them in the form of thin films called biofilms. Biofilms that grow in porous media are relevant to several industrial and environmental processes such as wastewater treatment and CO2 sequestration. We used Pseudomonas fluorescens, a Gram-negative aerobic bacterium, to investigate biofilm formation in a microfluidic device that mimics porous media. The microfluidic device consists of an array of micro-posts, which were fabricated using soft-lithography. Subsequently, biofilm formation in these devices with flow was investigated and we demonstrate the formation of filamentous biofilms known as streamers in our device. The detailed protocols for fabrication and assembly of microfluidic device are provided here along with the bacterial culture protocols. Detailed procedures for experimentation with the microfluidic device are also presented along with representative results.

Protocols for the study of biofilm formation in a microfluidic device that mimics porous media are discussed. The microfluidic device consists of an array of micro-pillars and biofilm formation by Pseudomonas fluorescens in this device is investigated.

Several bacterial species possess the ability to attach to surfaces and colonize them in the form of thin films called biofilms. Biofilms that grow in ...

Controlled Microfluidic Environment for Dynamic Investigation of Red Blood Cell Aggregation

Blood, as a non-Newtonian biofluid, represents the focus of numerous studies in the hemorheology field. Blood constituents include red blood cells, white blood cells and platelets that are suspended in blood plasma. Due to the abundance of the RBCs (40% to 45% of the blood volume), their behavior dictates the rheological behavior of blood especially in the microcirculation. At very low shear rates, RBCs are seen to assemble and form entities called aggregates, which causes the non-Newtonian behavior of blood. It is important to understand the conditions of the aggregates formation to comprehend the blood rheology in microcirculation. The protocol described here details the experimental procedure to determine quantitatively the RBC aggregates in microcirculation under constant shear rate, based on image processing. For this purpose, RBC-suspensions are tested and analyzed in 120 x 60 &#181;m poly-dimethyl-siloxane (PDMS) microchannels. The RBC-suspensions are entrained using a second fluid in order to obtain a linear velocity profile within the blood layer and thus achieve a wide range of constant shear rates. The shear rate is determined using a micro Particle Image Velocimetry (&#181;PIV) system, while RBC aggregates are visualized using a high speed camera. The videos captured of the RBC aggregates are analyzed using image processing techniques in order to determine the aggregate sizes based on the images intensities.

The protocol described details an experimental procedure to quantify Red Blood Cell (RBC) aggregates under a controlled and constant shear rate, based on image processing techniques. The goal of this protocol is to relate RBC aggregate sizes to the corresponding shear rate in a controlled microfluidic environment.

Blood, as a non-Newtonian biofluid, represents the focus of numerous studies in the hemorheology field. Blood constituents include red blood cells, white ...

Analyzing Mixing Inhomogeneity in a Microfluidic Device by Microscale Schlieren Technique

In this paper, we introduce the use of microscale schlieren technique to measure mixing inhomogeneity in a microfluidic device. The microscale schlieren system is constructed from a Hoffman modulation contrast microscope, which provides easy access to the rear focal plane of the objective lens, by removing the slit plate and replacing the modulator with a knife-edge. The working principle of microscale schlieren technique relies on detecting light deflection caused by variation of refractive index1-3. The deflected light either escapes or is obstructed by the knife-edge to produce a bright or a dark band, respectively. If the refractive index of the mixture varies linearly with its composition, the local change in light intensity in the image plane is proportional to the concentration gradient normal to the optical axis. The micro-schlieren image gives a two-dimensional projection of the disturbed light produced by three-dimensional inhomogeneity.
To accomplish quantitative analysis, we describe a calibration procedure that mixes two fluids in a T-microchannel. We carry out a numerical simulation to obtain the concentration gradient in the T-microchannel that correlates closely with the corresponding micro-schlieren image. By comparison, a relationship between the grayscale readouts of the micro-schlieren image and the concentration gradients presented in a microfluidic device is established. Using this relationship, we are able to analyze the mixing inhomogeneity from associate micro-schlieren image and demonstrate the capability of microscale schlieren technique with measurements in a microfluidic oscillator4. For optically transparent fluids, microscale schlieren technique is an attractive diagnostic tool to provide instantaneous full-field information that retains the three-dimensional features of the mixing process.

Herein, we describe a procedure that employs microscale schlieren technique to measure mixing inhomogeneity in a microfluidic device. Through calibration, distribution of concentration gradient can be derived from the micro-schlieren image.

In this paper, we introduce the use of microscale schlieren technique to measure mixing inhomogeneity in a microfluidic device. The microscale schlieren ...

Multi-step Variable Height Photolithography for Valved Multilayer Microfluidic Devices

Microfluidic systems have enabled powerful new approaches to high-throughput biochemical and biological analysis. However, there remains a barrier to entry for non-specialists who would benefit greatly from the ability to develop their own microfluidic devices to address research questions. Particularly lacking has been the open dissemination of protocols related to photolithography, a key step in the development of a replica mold for the manufacture of polydimethylsiloxane (PDMS) devices. While the fabrication of single height silicon masters has been explored extensively in literature, fabrication steps for more complicated photolithography features necessary for many interesting device functionalities (such as feature rounding to make valve structures, multi-height single-mold patterning, or high aspect ratio definition) are often not explicitly outlined. 
Here, we provide a complete protocol for making multilayer microfluidic devices with valves and complex multi-height geometries, tunable for any application. These fabrication procedures are presented in the context of a microfluidic hydrogel bead synthesizer and demonstrate the production of droplets containing polyethylene glycol (PEG diacrylate) and a photoinitiator that can be polymerized into solid beads. This protocol and accompanying discussion provide a foundation of design principles and fabrication methods that enables development of a wide variety of microfluidic devices. The details included here should allow non-specialists to design and fabricate novel devices, thereby bringing a host of recently developed technologies to their most exciting applications in biological laboratories.

Multilayer microfluidic devices often involve the fabrication of master molds with complex geometries for functionality. This article presents a complete protocol for multi-step photolithography with valves and variable height features tunable to any application. As a demonstration, we fabricate a microfluidic droplet generator capable of producing hydrogel beads.

Microfluidic systems have enabled powerful new approaches to high-throughput biochemical and biological analysis. However, there remains a barrier to ...

Microfluidic Platform with Multiplexed Electronic Detection for Spatial Tracking of Particles

Microfluidic processing of biological samples typically involves differential manipulations of suspended particles under various force fields in order to spatially fractionate the sample based on a biological property of interest. For the resultant spatial distribution to be used as the assay readout, microfluidic devices are often subjected to microscopic analysis requiring complex instrumentation with higher cost and reduced portability. To address this limitation, we have developed an integrated electronic sensing technology for multiplexed detection of particles at different locations on a microfluidic chip. Our technology, called Microfluidic CODES, combines Resistive Pulse Sensing with Code Division Multiple Access to compress 2D spatial information into a 1D electrical signal. In this paper, we present a practical demonstration of the Microfluidic CODES technology to detect and size cultured cancer cells distributed over multiple microfluidic channels. As validated by the high-speed microscopy, our technology can accurately analyze dense cell populations all electronically without the need for an external instrument. As such, the Microfluidic CODES can potentially enable low-cost integrated lab-on-a-chip devices that are well suited for the point-of-care testing of biological samples.

We demonstrate a microfluidic platform with an integrated surface electrode network that combines resistive pulse sensing (RPS) with code division multiple access (CDMA), to multiplex detection and sizing of particles in multiple microfluidic channels.

Microfluidic processing of biological samples typically involves differential manipulations of suspended particles under various force fields in order to ...