High-Aspect Ratio Si Neural Shafts: Fabrication and Brain Implantation

This paper presents a simple micromachining process to fabricate 2-D devices consisting of up to 20-mm-long shafts for neural applications. The manufacturing technology was mainly based on traditional blade dicing, normally used for wafers individualization into chips/devices in semiconductor and micro-electro-mechanical systems technologies. Here, it is demonstrated how a fully mechanical cutting technology is applied to the successful manufacture of challenging components with high-aspect ratio devices up to 41:1. Several other aspect ratio shafts (lengths varying between 5 and 20 mm) were produced and tested, for both the single-shaft and array devices. Mechanical characterization tests evaluated the devices robustness. Compressive strength tests for single-shaft 20-mm long shafts showed good longitudinal resistance to fracture, withstanding 28 N before breaking. Longitudinal forces play the key role while implanting the shaft inside the brain. Moreover, it was measured the load required to implant and extract 20-mm five-shaft array devices in two different mediums: 0.6% agar gel and calf cadaver brain. Maximum average insertion forces were 23 and 59 mN per shaft at 180 mm.min
^-1
for agar and cadaver brain mediums, respectively. Overall, by enhancing the performance of a purely mechanical machining tool, the micro manufacture of high-aspect ratio silicon shafts for neuroscience applications was demonstrated.