An EWOD Droplet Microfluidic Chip with Integrated Local Temperature Control for Multiplex Proteomics

We present a microfluidic chip for multiplex thermal processing of discrete micro- and nano-liter sample droplets driven by electrowetting-on-dielectric (EWOD). The system features local temperature control integrated on chip in addition to the basic fluidic functionalities previously reported for EWOD devices [1]. Multifunctioning indium-tin-oxide (ITO) electrodes serve as optically transparent resistive heaters, temperature sensors, and EWOD actuation pads. With a 1 μL sample, heaters reach programmed set points in a few seconds and stabilize to ±1 °C. We demonstrate automated on-chip proteomics sample processing and direct characterization by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The results, showing increased insulin disulfide reduction efficiency with heater temperatures from 22 to 130 °C, highlight the efficacy of the chip.