Reproducible fabrication of liquid metal droplets via electromigration and FIB sputtering in SEM

Abstract The capability to precisely fabricate and manipulate small-scale liquid metal droplets is important for the development of emerging technologies in the fields of micro-robotics, printable electronics, biomedical engineering, and nanocharacterization. However, the reproducible fabrication of liquid metal droplets with diameters at the micro- and sub-micrometer scale at a precisely defined location remains a key challenge towards realizing these applications. In this study, we demonstrate that sub-micron diameter liquid metal droplets can be fabricated in a reproducible manner via the combination of an electromigration and focused ion beam (FIB)-induced sputtering process. Electromigration is used to generate droplets at specific locations, and FIB sputtering is used to control the final diameter of the droplets. Using Galinstan as a case study, the method is established by analyzing the actual sputtering yield of Galinstan processed with different FIB parameters. The reproducibility of fabricating liquid metal droplets with a radius of 10 $$\upmu$$ m and 5 $$\upmu$$ m is experimentally investigated, resulting in standard deviations of 0.168 $$\upmu$$ m and 0.63 $$\upmu$$ m, respectively. The evaluated fabrication method is therefore expected to be well suited for developing liquid metal-based robotic actuators, drug delivery devices, and contact angle measurement (CAM) techniques carried out inside the scanning electron microscope (SEM).