Implantable probe with split anchors via residual stress and induced cell growth with gelatin nanofibres

A bipolar electrode probe used for implantable nerve stimulation treatments in minimally invasive surgeries is presented. The probe is composed of a flexible printed circuit substrate and a patterned SU-8 film. This probe features a three-dimensional (3D) tweezer-like mechanism opened by residual stress from the SU-8 film, designed to fix the probe in the tissue surrounding a target nerve. Stripes on the SU-8 film direct the net residual stress in a single direction to form a curve. The holding strengths of the probes with different deformations are defined and measured by a tensile test. Results show that the fixing ability of a 3D probe is better than a plane probe. The probes with curvature heights between 13 and 14 mm have a maximum average breaking force of 0.258 N, which is 16.3 and 13.1% higher than the probes with curvature heights between 9 and 10 mm and between 10 and 11 mm, respectively. In addition, a film of gelatin fibrous membrane, produced by electrospinning, covers the fixed ends of the probe´s anchors and acts as cell scaffolds to induce cell growth, which help to ensure long-term fixation in the body. 3T3 fibroblast cells are grown to verify the scaffold effect of the fibrous membrane.