Fabrication of force sensitive penetrating electrical neuroprobe arrays

MEMS-based penetrating micro-scale probe electrodes have been used in numerous electrophysiological measurements. However, it is necessary to quantitatively study probe-induced stress on the tissue/neurons and the damage during the probe penetration. Here we propose a vertically-aligned electrical recording neuroprobe array each with the force detection capability during the probe penetration into biological samples (Fig. 1). We fabricated the force sensitive probe array based on piezoresistive p-type silicon probes (∼0.9 Ω·cm) with the length of 60 μm and the diameter of 5 μm. The p-type silicon probe array was vertically assembled over an n-type silicon island by using in-situ doping vapor-liquid-solid (VLS) growth technology. Each probe has two terminal interconnections at the tip and the base formed by three-dimensional metallization process. The probe resistance for the piezoresistance effect in silicon was confirmed by measuring the current-voltage characteristics of vertically assembled individual probes. During the probe penetration, the probe array can also be used for multi-site electrical recordings of neural activities via Pt-black electrodes at probe-tips with a low impedance of 14 KΩ at 1 kHz.