Accurate DMA method for determining glass transition temperature of filled polymers at the microscale via micropillar compression

A micropillar compression–nanoDMA method is developed for microscale T g measurement. • Flat-ended indenter averages local stiffness variations in filled polymers. • Smooth modulus and tan delta curves enable unambiguous T g identification. • T g is reliably determined from storage modulus onset, loss modulus peak, and tan delta peak. • The method applies to heterogeneous polymers in microelectronics and composites. The glass transition temperature (T g ) is a critical parameter for evaluating the thermal and mechanical stability of amorphous polymers, but accurate measurement for heterogeneous filled polymers at the microscale remains challenging. In this work, we present an accurate DMA method for determining the T g of filled polymers at the microscale via micropillar compression. Micropillars of a home-made silica-filled epoxy resin were fabricated by focused ion beam (FIB) and tested using a flat-ended diamond indenter on a nanoDMA instrument equipped with a high-temperature stage. The new method yields markedly smoother storage modulus, loss modulus, and tan delta curves, with greatly reduced point-to-point scatter, enabling clear identification of T g from the onset of storage modulus drop, the loss modulus peak, and the tan delta peak. In contrast, the conventional nanoDMA method exhibits substantial data scatter that obscures the glass transition.