Abstract
Soft materials, liquids, and biological tissues are of increasing interest as thermal materials for applications in energy storage, electrical/electrochemical systems, and cryopreservation, but thermal characterization of these materials can be challenging experimentally. Here, we extend the robust 3-omega method, which is traditionally based on a planar form factor with external sample contact, to a microfabricated needle-form sensor that can be plunged directly into a sample. We further demonstrate the reusability of this sensor, the ability to easily make thermal contact by plunging the sensor into the center of a sample, and the ability to sample systems undergoing phase transformations. We do so via application to solid ice as well as 4 representative materials at room temperature: water, glycerol, paraffin, and chicken liver, thereby demonstrating the sensor's utility for liquids, soft solid materials, and phase change materials. Data analysis is conducted by fitting to a three dimensional numerical model of the sensor and sample. These experiments show very good agreement of within 3% of literature values for thermal conductivity for the explored materials, which range in thermal conductivity from approximately 0.3 W/mK to 2.3 W/mK.