Lithography-free, low-cost, picowatt-resolution calorimeter for micro and nanoscale thermal characterization

Abstract

Advanced high-resolution thermal characterization tools for micro- and nanoscale materials often rely on costly iterative design and time-consuming microfabrication steps such as lithography and etching. While providing valuable insights, this creates significant technical barriers to the wide adoption of these techniques beyond the specialized research areas of heat transfer and thermal sensing. Furthermore, microfabricated calorimeters with typical suspended thermal bridge designs lack multi-degree-of-freedom manipulation of materials and suffer from low mechanical stiffness for robust long-term operation. This study presents a micro and nanoscale thermal characterization platform that eliminates the need for lithography while achieving ultrahigh thermal resolution. Using a four-thermistor configuration and noise mitigation technique, we demonstrated a peak-to-peak temperature resolution of ± 12 µK and a heat resolution of 250 pW at room temperature. The calorimeter device also features high stiffness in all directions and offers three degrees of freedom for high-precision positioning and manipulation. We validated the sensing capability of this platform by measuring the thermal conductivity of microscale polymer fibers, wherein the background radiative thermal conductance and thermal contact resistance are evaluated concurrently. This work's low-cost, easy-to-manufacture calorimeter paves the way to expand the accessibility of high-sensitivity thermal characterization tools in various applications, such as new material discovery, thermoelectrics, and environmental and biochemical sensing.