Thermal diffusivity microscope: Zooming in on anisotropic heat transport.

Anisotropic heat-conducting materials play crucial roles in designing electronic, optoelectronic, and thermoelectric devices, where temperature and thermal stress are important. Despite substantial research efforts, a major obstacle to determining the anisotropic thermal diffusivity tensor in polycrystalline systems is the need for a robust, direct, and nondestructive technique to distinguish between distinct thermal diffusivities. Here, we demonstrate a conceptually unique thermal diffusivity microscope capable of performing high-resolution local measurements of anisotropic thermal diffusivity.

Cell Structure in LPBF 316L-Microstructural Heterogeneity, Thermal Stability, and Mechanical Properties.

The microstructure of additively manufactured 316L stainless steel is hierarchical, and on a fine scale, it contains cell structures and dislocations. These microstructures define the mechanical properties, and it is thus of importance to quantify them and understand their thermal stability. This study investigates the heterogeneity of the microstructure in laser powder bed-fused 316L with a focus on variations in the cell and dislocation structures through the sample thickness along the build direction.

MEMS micro-coils for magnetic neurostimulation.

Micro-coil magnetic stimulation of brain tissue presents new challenges for MEMS micro-coil probe fabrication. The main challenges are threefold; (i) low coil resistance for high power efficiency, (ii) low leak current from the probe into the in vitro experimental set-up, (iii) adaptive MEMS process technology because of the dynamic research area, which requires agile design changes. Taking on these challenges, we present a MEMS fabrication process that has three main features; (i) multilayer resist lift-off process to pattern up to 1800-nm-thick metal films, and special care is taken to obtain high conductivity thin-films by physical vapor deposition, and (ii) all micro-coil Al wires are encapsulated in at least 200 nm of ALD alumina and 6-μm-thick parylene C such the leak resistance is high (>210 GΩ), (iii) combining a multi-step DRIE process and maskless photolithography for adaptive design and device fabrication.