Fabrication of photothermally actuated microheater with SU-8/Cu composite

The photothermally actuated microheaters have been studied for various applications. In particular, microheaters using composites mixed with polymer and particles were developed for a microrobot and thermally responsive structures. However, the structures have been fabricated by soft lithography process, which needs multiple steps. Here, we propose a microheater fabricated using a photosensitive composite, which is a mixture of the photosensitive resin SU-8 and Cu microparticles. The composite structures fabricated by one step photolithography exhibited a rise of temperature due to the photothermal effect, which was induced by the observation system of an inverted fluorescent microscope. In evaluating the patterning accuracy of the composite, although the line-and-space pattern formed was a minimum of 30 µm, the fabricated patterns involved a dimensional error of 5%–25%. The composite with 50 wt% Cu particles of 1 µm showed a maximum temperature of 55.7 °C in our experiments. The micropatterns of the microheater were fabricated and showed a rise of temperature of 16 °C–46 °C. In addition, the time response of the rising temperature was approximately 1 s. Thus, the proposed microheater could be useful for applications in which a change of temperature in the range of 10 °C–40 °C.