A 3D printed intracortical microprobe with automatic effective stiffness control

Objective

A mechanical mismatch between a microprobe implanted in the brain and its surrounding soft tissue facilitates tissue damage and microprobe failure due to brain micromotion. Utilising soft intracortical microprobes with elastic moduli close to that of the brain may reduce tissue damage and enhance the longevity of the microprobes. Providing temporary stiffness for soft microprobes is a dominant method to prevent buckling during insertion. Nevertheless, the inability of these methods to efficiently control the stiffness results in inaccurate positioning or tissue damage.

Approach

This paper presents an engineered interface between the microprobe and an inserter/neural tissue to provide an instant switch between the stiff and soft modes of the microprobe.

Main results

The microprobe's equivalent elastic modulus increases to ≈4.2 GPa during insertion and positioning due to an applied compressive force by an inserter and instantly returns to ≈98 kPa after positioning. The 3D printed microprobe is experimentally tested and inserted into a lamb brain without buckling, confirming the feasibility of the design proposed in this study.

Significance

The cross-sectional area of the proposed microprobe is approximately 70 % smaller than that of the existing counterpart, resulting in less tissue damage during insertion and operation.