Electroadhesive stamp assembles tiny electronic components

Small electronic parts like circuit boards and display components are often assembled using robotic grippers that can place multiple elements into precise configurations. But advances in electronics are demanding ever-smaller components, and there’s a limit to how far traditional mechanical grippers can be miniaturized. At very small scales, surface forces tend to dominate, presenting a challenge to picking up and placing objects by traditional means. So scientists are looking for alternatives to help assemble objects at tiny scales. Researchers at the Massachusetts Institute of Technology, the Korea Advanced Institute of Technology, and the University of Pennsylvania have developed a nanotube-based, voltage-activated surface that lets them manipulate objects as small as 20 nm wide without requiring heat or chemical reactions (Sci. Adv. 2019, DOI: 10.1126/sciadv.aax4790). The stamp is made of vertically aligned carbon nanotubes coated in aluminum oxide, a dielectric material. When a small voltage is applied, the stamp electrostatically attracts the target object. Once the object is moved into place, researchers can release it by turning off the voltage. The researchers varied the density of tubes and thickness of coating to achieve a high on-off ratio of stickiness. They used the stamp to pick up and arrange silver nanowires, polymer and metal nanoparticles, and light-emitting diode chiplets.