Thermocouple-integrated resonant microcantilever for on-chip thermogravimetric (TG) and differential thermal analysis (DTA) dual characterization applications.

Abstract

This work presents an integrated microsensor that combines the dual characterization capabilities of thermogravimetric analysis (TGA) and differential thermal analysis (DTA). We integrated two pairs of thermocouples, heating resistors, and resonant drive/detection resistors into a single microcantilever, where the cantilever resonant frequency shifts respond to the mass change and the output voltage of the integrated thermocouples respond to the sample temperature. This integration enables programmable temperature control, temperature variation, and mass detection on a single chip. Our chip can achieve heating and cooling rates above 600 °C/min, which is significantly faster than commercial instruments with satisfactory measurement accuracy. The integrated polysilicon thermocouples bring high power responsivity of 6 V/W, making them suitable for highly sensitive DTA measurements on a chip. Moreover, the cantilever offers picogram (10^-12g) level mass resolution, reducing sample consumption from milligrams to nanogram levels. Additionally, the on-chip sample heating allows for easy observation of sample morphological evolution during heating under an optical microscope. We validated the dual functionality by conducting TGA measurements on a standard sample of calcium oxalate monohydrate (CaC₂O₄ ∙ H₂O) and DTA measurements on high-purity indium (In) and tin (Sn). The results indicate consistent measurements with the true values of the standard sample and high measurement efficiency. Our integrated cantilever chip is anticipated to have broad applications in high-performance and efficient TGA and DTA characterization.