Microheater isolation characterisation to aid the optimisation of a MEMS Leidenfrost engine

This paper reports on the implementation of test structures to characterize the design of a microheater that facilitates localized heating to power a Leidenfrost micro-engines. The test structures are designed to characterize the effect on heat transfer of trenches etched into the silicon substrate. With no trench, the temperature difference is $\triangle \mathrm{T}=11.9$ oC. The temperature measured across the 412 $\mu \mathrm{m}$ deep “long” trench was 43.6 °C while it was 40.4 °C for the “short” trench. The results show that increasing the depth of the trench increases the temperature difference across the trench $(19.9{}^{\circ}\mathrm{C}$ increase for going from 73 $\mu \mathrm{m}$ to 412 $\mu \mathrm{m}$, for the “short” channel) while the length of the trench has a much less significant effect $(3.2{}^{\circ}\mathrm{C}$ increase from “short” to “long” trench, for a depth of 412 $\mu \mathrm{m})$. The test structure measurements agreed well with simulation results confirming the validity of using computer aided design as an integral part in the development of microheater designs.