3D soft microbump electrodes for elastic interaction with brain tissue

Flexible implantable electrodes provide unprecedented opportunities for gentle mechanical interaction with soft neural tissues to acquire stable electrophysiological signals and reduce risk of tissue inflammatory response. Most electrocorticography (ECoG) electrodes adopt polymer film or silicone as substrate, with thickness sacrifice or poor micromachining precision, respectively. Besides, the distance of recessed electrode site to cortical surface leads to signal degradation. Here, we report a 3D polyimide-based electrode array on soft microbumps (height, 327 µm), with buffering contact capability and reliable mechanical strength that alleviates the mismatch from dental cement or cranial window. We demonstrate the reshaping processes of conventional 2D sites (diameter, 200 µm) into 3D protruding structure by stress-free preforming and silicone casting. The 3D soft microbump electrodes (SMBE) remain well undergoing whether cyclic voltammetry scanning or cyclic compression. The acute implanted SMBE array has shown sensitive response to whisker pulling and insusceptible stability by external force of anesthetic rats.