Capillary flow of blood in a microchannel with differential wetting for blood plasma separation and on-chip glucose detection

Abstract

We report capillary flow of blood in a microchannel with differential wetting for the separation of a plasma from sample blood and subsequent on-chip detection of glucose present in a plasma. A rectangular polydimethylsiloxane microchannel with hydrophilic walls (on three sides) achieved by using oxygen plasma exposure enables capillary flow of blood introduced at the device inlet through the microchannel. A hydrophobic region (on all four sides) in the microchannel impedes the flow of sample blood, and the accumulated blood cells at the region form a filter to facilitate the separation of a plasma. The modified wetting property of the walls and hence the device performance could be retained for a few weeks by covering the channels with deionised water. The effects of the channel cross-section, exposure time, waiting time, and location and length of the hydrophobic region on the volume of the collected plasma are studied. Using a channel cross-section of 1000 × 400 m, an exposure time of 2 min, a waiting time of 10 min, and a hydrophobic region of width 1.0 cm located at 10 mm from the device inlet, 450 nl of plasma was obtained within 15 min. The performance of the device was found to be unaffected (provides 450 nl of plasma in 15 min) even after 15 days. The purification efficiency and plasma recovery of the device were measured and found to be comparable with that obtained using the conventional centrifugation process. Detection of glucose at different concentrations in whole blood of normal and diabetic patients was performed (using 5l of sample blood within 15 min) to demonstrate the compatibility of the device with integrated detection modules.

Capillary flow-driven microfluidic device with wettability gradient and sedimentation effects for blood plasma separation

“…To retain hydrophilicity, PDMS blocks (as shown in Fig. 2b) with h c  = 4 mm and d c  = 1 mm were stored in DI water under vacuum32. Contact angles were measured at three different locations ( y/h c  = 0, 0.25, 0.5) along the side wall on different days (0–20 days) after the exposure.…”

Surface tension driven flow of blood in a rectangular microfluidic channel: Effect of erythrocyte aggregation

“…26 Surface wetting properties induced by plasma can be maintained for a few weeks. 27 Combining TiO 2 films with O 2 plasma etching treatment, and/or UV activation 28 has been found to further enhance wetting properties of glass surfaces.…”

“…STD flows for diagnostic purposes have also been reported in the literature. Sneha Maria et al 27 devised a rectangular polydimethylsiloxane (PDMS) microchannel, with differential wetting properties, in order to separate the plasma and detect the glucose levels therein. In another study 35 an on-chip whole blood/plasma separator was developed using a combination of asymmetric nanoporous super-hydrophilic surfaces and patterned hydrophobic patches.…”

Potential Point-of-Care Microfluidic Devices to Diagnose Iron Deficiency Anemia

“…The commercialized technology discussed thus far remains limited in POC applications because they still require a sample transfer, concomitant expert handling, and separate readout system. Recently, Maria et al [ 53 ] demonstrated a self-built blood filter in a microchannel that comes with mixed hydrophilic-hydrophobic regions in a PDMS-based device. The device performs blood plasma separation for glucose detection.…”

“…( C ) Plasma collector by Liu et al group, from [ 49 , 50 ]. and ( D ) In-lab self-built Red Blood Cells (RBC) filter adapted from Reference [ 53 ].…”