Novel Integration Approach for In situ Monitoring of Temperature in Micro-direct Methanol Fuel Cell

Abstract

In this work, a porous silicon layer is fabricated as the gas diffusion layer (GDL) of a micro-direct methanol fuel cell (µDMFC) using micro-electro-mechanical-systems (MEMS) technology. Platinum is deposited on surface of the porous silicon layer to improve the electrical conductivity of the µDMFC. Physical vapor deposition (PVD) was utilized to deposit Pt metal and wet etching was adopted to form the conductive layer and micro-thermal sensors. The Pt acted both as a current collector and a micro-thermal sensor. We fabricated a resistance temperature detector (RTD) sensor for integration with the gas diffusion layer on the bipolar plate to measure the temperature inside the µDMFC. GDLs with pores of various sizes (10, 30, and 50 µm) were considered to test the performance of the µDMFC. A silicon wafer (500 µm) was etched using KOH wet etching to yield fuel channels with a depth of 450 µm and a width of 200 µm. Then, a porous silicon layer was formed by deep reactive ion etching (DRIE) to act as the GDL of the µDMFC. The experimental results obtained at various fuel flow rates, pore sizes and other operating conditions demonstrate that the maximum power density of the µDMFC is 1.784 mW/cm2, which was reached at 203 mV with 50-µm-diameter holes. The microsensor temperature was determined to be in the range from 20 to 46 °C and the resistance of the microsensor was in the range from 7.524 to 7.677 kΩ. Experimental results demonstrate that temperature is almost linearly related to resistance and that accuracy and sensitivity are 0.3 °C and 7.82×10-4/°C, respectively.