Temperature-Controlled Electrochemical Microsensors and Microsensor Arrays
In this work we present the design concepts, fabrication methods, and temperature characterization approaches for microfabricated, temperature-controlled electrodes. The use of modern microfabrication techniques provides several advantages by facilitating the construction of sensors with highly reproducible heating/electrochemical characteristics, the production of high spatial-density sensor arrays, and the compatibility of sensors with complementary microfluidic/MEMS components for sensing in ultra-small sample volumes. The sequential deposition of patterned metallic structures and insulating layers (e.g. SiO2) was used to fabricate Au disk electrodes (r ≤ 75 μm) with underlying platinum resistive heating elements as shown in Figure 1A. The small vertical electrode-heater separation (≲ 500 nm) allows for rapid and efficient heating of the electrode surface. Infrared and fluorescent temperature imaging techniques are used to evaluate temperature gradients and thermal response times, which impact sensor performance. We demonstrate temperature-dependent electrochemical measurements performed on model systems (e.g. Fe(CN)63-/4- and Ru(NH3)63+/2+) in which coupled heat and mass transport impart signal enhancement as shown in the cyclic voltammograms in Figure 1B. We also discuss the impact of various temperature control routines, such as temperature steps, pulses and oscillations, on electrochemical signal content.
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