Touch-Enabled Reversible Microfluidic Ultradense Chips for Convenient, High-Throughput Electrochemical Assays

Abstract

Here, we present a new approach to reversibly bond microfluidic polydimethylsiloxane (PDMS) channels on low-cost, reproducible, scalable, compact, and ultradense multisensor SU-8-coated chips toward high-throughput electrochemical assays. Based on putting the outlets at the bottom of PDMS, the method only needs manually attaching this substrate on a flat surface, thus offering simplicity, throughput, and reversibility. While a plasma-mediated approach failed to provide leakage-free bonding, the reversibly bonded devices presented a high adhesion strength, withstanding a pressure of at least 5.1 MPa. Because the approach is high-pressure tolerant and reversible, it can deliver both long-term analyses and ease of sampling in-channel material for posterior manipulation/characterization and even sensor regeneration. Importantly, the bonding also delivers long-term shelf life and reusability. Three proof-of-concept applications are presented: (i) the electrodeposition of different nanostructured microelectrodes, followed by their downstream characterization and electrochemical tests, (ii) the long-term proliferation and monitoring of colorectal and breast cancer cells through electrochemical cell adhesion assays, along with the following regeneration of sensors and drug susceptibility testing, and (iii) the electrode fouling-amenable determination of phosphate in synthetic body fluids (urine and saliva) for health assessment purposes. High-throughput assays were provided by the chips from fast analyses in series utilizing a hand-held one-channel potentiostat. For instance, 45 analyses could be completed within ∼135 s. One should also note that the approach is compatible with different materials. Hence, future studies can explore this generalizable dry bonding to produce other microfluidic systems for diverse applications.