MicroElectroThermoForming (μETF): One-step Versatile 3D Shaping of Flexible Microelectronics for Enhanced Neural Interfaces

Abstract Increasing the proximity of microelectrode arrays (MEA) to targeted neural tissues is crucial for establishing efficient neural interfaces for both recording and stimulation applications. This has been achieved by constructing protruding three-dimensional (3D) structures on top of conventional planar microelectrodes via additional micromachining steps. However, this approach adds fabrication complexities and limits the 3D structures to certain shapes. We propose a one-step fabrication of versatile microscopic 3D structures for thin-film MEAs via “microelectrothermoforming (µETF)” of thermoplastics, by utilizing 3D-printed molds to locally deform planar MEAs into desired protruding and recessing shapes. Electromechanical optimization of the µETF process enabled a 3D MEA with 80 µm protrusions and/or recession for 100 µm diameter. Its versatile shaping capabilities are demonstrated by simple and simultaneous forming of diverse 3D structures on a single MEA. The benefits of 3D MEA are evaluated in retinal stimulation through numerical simulations and ex vivo experiments, confirming a threshold lowered by 1.7 times and spatial resolution enhanced by 2.2 times.