Electrochemically Tunable 3 <i>ω</i> Platform for Thermal Characterization and Composition Sensing in Liquids

This work presents a four‐channel suspended‐microwire platform that couples the three‐omega (3 ω ) method with a three‐electrode electrochemical cell for in situ, postfabrication signal control and the characterization of liquids based on their thermal conductivity. The sensing gold microwires serve simultaneously as heaters, thermometers, and working electrodes, enabling anodic etching via cyclic voltammetry to adjust the wire resistance and the 3 ω ‐voltage amplitude across 1–100 Hz. Nine CV cycles are identified as a practical operating point. Measurements in water, ethanol, and isopropyl alcohol (IPA) set practical current limits, 0.6 A for water and 0.4 A for ethanol and IPA, using the microwires under study. Frequency sweeps in the mid‐band (4–30 Hz) are analyzed with a cylindrical Bessel‐function model. Finally, a calibration curve of water‐ethanol mixtures is measured with commercial beverages (beer, wine, and vodka), aligning with the same 3 ω trend, demonstrating composition readout from the thermal channel in under 30 s.