MICROFLUIDIC PAPER-BASED ANALYTICAL DEVICES USING PLASMA PROCESSES
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Using pentafluoroethane (PFE) and O2 as precursor gases, plasma (glow discharge) processes were developed to fabricate fully enclosed and semi-enclosed microfluidic paper-based analytical devices (μ-PADs) as a platform to conduct colorimetric detection of biomarkers for low-cost disease diagnostics. Results indicate that fully enclosed devices can be easily packaged using non-porous adhesive tape to inhibit sample contamination and evaporation thus making the proposed μ-PADs more suitable for field use. A glucose sensor was developed to demonstrate the functionality of the μ-PAD. Furthermore, flow control functionality was incorporated in fully enclosed devices to automate multistep protocol assays such as enzyme-linked immunosorbent assays. It was shown that by varying the O2 plasma etching time, the amount of residual hydrophobic fluorocarbon and thus the fluid flow speed can be varied inside the fully enclosed channels. As a proof-of-concept, a device that can sequentially deliver and react three reagents each with different pH to a detection zone deposited with a pH indicator was designed and fabricated. Additionally, a plasma process to fabricate semi-enclosed μ-PADs directly on commercially available RBC separation (from whole blood) membrane (Whatman LF1 membrane) was developed. Using cellulose nanocrystal modification of LF1 membrane and by bonding the μ-PAD with adhesive tape, a device that can detect disease biomarkers such as glucose and albumin in a whole blood sample without the need for external equipment was developed. Moreover, the compatibility of semi-enclosed μ-PADs with a cell-free expression system for zinc diagnostic in whole blood was tested.