Assessing reusability of microfluidic devices: Urinary protein uptake by PDMS-based channels after long-term cyclic use

In the search for transformative technologies for person-centered health monitoring, reusability of microfluidic chips would be a critical design consideration in many biomedical applications. With this unmet need in mind, in this study, we develop and validate a novel microfluidic platform for automated sample pumping with an integrated channel-cleaning procedure. The proposed system leverages micropumps and on-chip solenoid valves to dynamically control fluid flow. We provide a thorough characterization of the custom-designed chip, including quantitative measures of the protein uptake by the chip, as well as cross-contamination using both simulated samples and human urine samples. The effectiveness of the cleaning procedure is assessed by testing the samples collected from the cleaning chip with commercially available urine dipstick protein tests. The results of the longitudinal protein level measurement of the urine samples after the cleaning cycles show high accuracy of protein measurement and negligible protein cross-contamination. Additionally, the cleaning procedure after pumping each sample results in a very low protein uptake (150 ng/cm(2)). We have also demonstrated that the efficiency of the automated cleaning microfluidic device can be further improved by an anti-fouling coating via PLL-g-PEG pretreatment and a posttreatment via Trypsin. The developed platform could potentially be further miniaturized and integrated into point-of-care devices to provide an effective cleaning process and to enable the reusability of microfluidic devices.