Laser-Induced Forward Transfer of SU-8 Microdisks as Carriers of Metallic Microdevices

Laser-induced forward transfer (LIFT) is a digital additive manufacturing technique that uses a pulsed laser to transfer various materials from a donor film to a receiver substrate placed in close proximity. In this work, we investigate the transfer of SU-8 microdisks on which metallic microdevices have been patterned. These components are directly fabricated on the donor substrate and their performance was evaluated after the transfer by LIFT. The influence of laser fluence, SU-8 thickness and donor-to-receiver gap on the SU-8 microdisk transfer was investigated. Successful and damage-free transfer of SU-8 microdisks can be achieved with optimized parameter combinations. The adhesion between the transferred SU-8 microdisks and different receivers was also assessed. These tests indicate that the adhesion without additional glue between SU-8 and the receiver is adequate for standard applications. The assembly of SU-8 microdisks to form multi-layer structures was also demonstrated. Large-scale transfer of a $40\times 40$ SU-8 microdisk array within 20 minutes was achieved to assess the transfer scalability of the LIFT process. As an application example, we transferred a temperature sensor onto a receiver with pre-patterned contact electrodes and characterized its performance. Our work opens a route to directly manufacturing wafer-scale microdevices on the donor substrate and enables the heterogeneous integration of such devices onto numerous functional surfaces with deterministic distribution and scale.[2024-0134]