LAUSR

Significance One of the key aspects of materials discovery is understanding the way heat moves through a material, with applications across the scientific spectrum from superconducting phase transitions to binding mechanisms in amino acids. However, the smaller the sample under study (e.g., small crystals of quantum materials), the more difficult it becomes to measure heat flow with standard macroscopic calorimeters. Here, we show that we can use optical wireless integrated circuits (OWiCs) as microscopic calorimeters for noninvasive, in situ, measurements of the thermal conductivity, diffusivity, and heat capacity of almost any material, from aerogel to silicon, on samples down to 100 ng, including across phase transitions. The OWiCs are an all-purpose thermal measurement tool that can transform the way scientists explore and discover new materials.