Single-nanowire-morphed mechanical slingshot for directional shooting delivery of micro-payloads

Abstract

Stretching elastomer bands to accumulate strain energy, for a sudden projectile launching, has been an old hunting skill that will continue to find new applications in miniaturized worlds. In this work, we explore the use of highly resilient and geometry-tailored ultrathin crystalline silicon nanowires (SiNWs) as elastic medium to fabricate the first, and the smallest, mechanical slingshot. These NW-morphed slingshots were first grown on planar surface, with desired layout, and then mounted upon standing pillar frames, with a unique self-hooking structure that allows for a facile and reliable assembly, loading and shooting maneuvers of microsphere payloads. Impressively, the elastic spring design can help to store 10 times more strain energy into the NW springs, compared to the straight ones under the same pulling force, which has been stronger enough to overcome the sticky van de Waals (vdW) force at the touching interfaces that otherwise will hinder a reliable releasing onto soft surface with low-surface energy or adhesion force, and to achieve a directional shooting delivery of precise amount of tiny payload units onto delicate target with the least impact damage. This NW-morphing construction strategy provides also a generic protocol/platform to fast design, prototype and deploy new nanoelectromechanical and biological applications at extremely low costs.

Growth Control of In-Plane Silicon Nanowires via Catalyst Size-Dependent Laser Heating for High-Performance Electronics

“…The as-grown SiNWs have been widely applied in field effect transistors (FETs), 29−31 logic, 32 sensing, 33,34 and NEMS devices,. 35,36 Since the growth temperature in IPSLS mode is only required at the droplet level, we recently developed a self-selected laserdroplet-heating strategy to elevate temperature for the in-plane growth of high-quality SiNWs, 37 where the leading In droplets show much stronger absorption to infrared laser (808 nm) than those of the surrounding a-Si:H and glass or silicon wafer. Thanks to the direct heating of the leading droplets, the quality of the as-grown SiNWs has been proven to be equivalent to those produced with high-temperature (>600 °C) environmental heating.…”

“…To address the self-localization challenge, we have developed an in-plane solid–liquid–solid (IPSLS) growth strategy in our previous study, − where the indium (In) catalyst droplets move along a predesigned guiding edge and absorb a hydrogenated amorphous Si (a-Si:H) layer to produce SiNW arrays, as illustrated in Figure a. The as-grown SiNWs have been widely applied in field effect transistors (FETs), − logic, sensing, , and NEMS devices,. , Since the growth temperature in IPSLS mode is only required at the droplet level, we recently developed a self-selected laser-droplet-heating strategy to elevate temperature for the in-plane growth of high-quality SiNWs, where the leading In droplets show much stronger absorption to infrared laser (808 nm) than those of the surrounding a-Si:H and glass or silicon wafer. Thanks to the direct heating of the leading droplets, the quality of the as-grown SiNWs has been proven to be equivalent to those produced with high-temperature (>600 °C) environmental heating.…”