Thermal characteristics of temperature-controlled electrochemical microdevices

Abstract

The development of novel, miniaturized sensing systems is driven by the demand for better and faster chemical measurements with lower power consumption and smaller sample sizes. Emerging miniature sensors, or microsensors, also offer rapid thermal and diffusive transport characteristics. For instance, temperature changes, during both heating and cooling, can be achieved on micrometer-scale surfaces much more rapidly than on bulk, macro-scale surfaces. While these rapid thermal characteristics have been most successfully exploited to date in gasphase sensing devices, the prospect of developing analogous microfabricated, temperaturecontrolled microsensors for use in aqueous, or solution-phase, environments has been less explored. In this work, electrodes with underlying microheaters were designed and fabricated, and thermal characterization was performed using temperature imaging, transient temperature measurements, and theoretical modeling to determine temperature distributions and thermal response times in both gas-and solution-phase environments. These results will guide the development of solution-phase electrochemical sensors. Temperature-controlled electrochemical characterization was performed using cyclic voltammetry of a model analyte, hexaamineruthenium(III) chloride, to demonstrate the use of the multilayer, microfabricated devices, which consisted of a gold disk electrode and an underlying microheater. Electrochemical signals were enhanced by up to a factor of three at elevated temperatures (up to 81 °C) compared to the those measured at room temperature (21 °C). This improved signal at elevated temperatures was explained by finite element method calculations that accounted for both temperature-dependent diffusion and thermal convection near the heated electrode surface.

Transport and Durability of Energy Storage Materials Operating at High Temperatures

“…Finally, we foresee new opportunities to expand the applications of energy storage materials and devices, taking advantage of functional operations at high temperatures. Examples include fast charging, thermally chargeable SCs for renewable energy storage, and self-operating thermal sensors …”

Conformational Changes of Immobilized Polythymine due to External Stressors Studied with Temperature-Controlled Electrochemical Microdevices

“…fused-silica wafer. Each has an embedded Pt serpentine structure which functions as a platinum resistance thermometer (PRT) and has also been used as an integrated resistive microheater in other studies . A SiO 2 insulation layer of thickness 1 μm and electrodes of Pt and Au were located over the PRT, as reported previously .…”

“…Each has an embedded Pt serpentine structure which functions as a platinum resistance thermometer (PRT) and has also been used as an integrated resistive microheater in other studies. 41 A SiO 2 insulation layer of thickness 1 μm and electrodes of Pt and Au were located over the PRT, as reported previously. 19 The electrodes included an Au working electrode (WE), where the polyT is immobilized ( Figure 1 b), a Pt quasi-reference electrode (RE), which establishes an electrical potential against which all other potentials are measured, and a Pt counter electrode (CE), which is used in conjunction with the WE to achieve current flow.…”

Ligand-Based Stability Changes in Duplex DNA Measured with a Microscale Electrochemical Platform

“…Previous studies by our group demonstrate the utility of microheater systems integrated with a three-electrode electrochemical cell to detect single or multiple base mismatches in immobilized duplex DNA [35] and to study temperature-induced enhancement of signals due to temperature-dependent diffusion and thermal convection in model redox systems [36]. Our platform is unique in having an individual embedded platinum heater integrated with each planar three-electrode set, thus positioning our methodology for easy scale-up to addressable arrays such as those for studying immobilized DNA under a variety of conditions.…”