Out-of-plane assembly of 3D neural probe arrays using a platform with SU-8-based thermal actuators

This paper describes an optimized out-of-plane assembly method based on a platform with integrated thermal actuators. The platform comprises cavities with overhanging gold clips embedded into a flexible polyimide (PI) cable. Planar micro components are inserted perpendicularly into the platform cavities and electrically connected to the PI cable by bending the gold clips into the cavities. In contrast to previous approaches using platforms of fixed cavity sizes [1-3], the new approach applies SU-8-based thermal actuators capable of widening the cavities during the assembly process by up to 9 μm for a temperature increase of 155 K. The directionally effective thermal expansion of nine actuator designs is evaluated experimentally and compared with finite element (FE) simulations. The optimized system design is successfully demonstrated with a three-dimensional (3D) neural probe array comprising 40 individually addressable electrodes.