A flexible neural implant was designed and fabricated using an novel integration approach that offers the advantages of both silicon and polymer based implants: high density electrodes and precise insertion on one side and mechanical flexibility suitable for reduced tissue strain due to micro-motion during chronic implantation on the other side. This was achieved by separating the device into silicon or polymer areas, depending on their desired functionality. The tip, where the recording and stimulation electrodes would be placed, was kept of silicon: a choice that doesn't call for any compromise to be made regarding the high density electrode and possible local circuit integration later on. The bevel shaped sharp silicon tip also proved to facilitate the probe insertion, offering a behavior very much similar to the classical rigid silicon probes. On the other side, most of the 1 cm long shank of the probe was made out of polyimide. This led to more than one order of magnitude reduction of the forces necessary to bend the shank. The flexible shank proved also to be more robust than silicon probes, sustaining significant deformation in any direction without fracture. The 9mm deep in-vivo implantation were successfully achieved without buckling for 10 µm/s and 100 µm/s insertion speeds.
Among the technological developments pushed by the emergence of 3D Stacked IC technologies, temporary wafer bonding and thinning have become key elements in device processing over the past years. While these elements are now mature enough for high-volume manufacturing, thin wafer debonding and handling still remain challenging. Hence this work focuses on a novel ZoneBOND approach to face these challenges.
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