Non-Contact Transfer Printing Enabled by an Ultrasonic Droplet Stamp

Transfer printing is an important material heterogeneous technique with unique capability for developing existing and envisioned electronic or optoelectronic systems. Here, a simple design of ultrasonic droplet stamp is reported featuring a water droplet on an acoustic resonator attached to a glass sheet, for developing an efficient non-contact transfer printing. The water droplet offers the benefits of a gentle and conformal contact, yielding an enough adhesion for a reliable pickup in the absence of ultrasound, and ejects a sub-droplet rapidly due to the Raleigh instability with the ultrasound for an easy non-contact printing. Experimental studies are carried out to investigate the transient response of ultrasonic droplet stamp under the action of ultrasound and showed that the proposed stamp exhibited extraordinary capabilities of damage-free pickup and receiver-independent printing. Demonstrations of the ultrasonic droplet stamp in transfer printing of thin inks with different materials and shapes onto various flat, curved and rough surfaces illustrate its great potential for heterogeneous integration and deterministic assembly.