Microwatt 3D printing of metal nanostructures via photothermally activated Coulombic potential

<title>Abstract</title> <p>Laser-based three-dimensional (3D) metal printing emerges as a transformative technology that enables fabrication of functional components for applications ranging from aerospace and automobile industries1 to micro-electronics2 and photonics3. Conventional approaches typically rely on high-power lasers to join metallic composites into complex geometries4,5. In addition to the unbearable cost of high-power lasers, however, intensive laser heating of the absorptive metallic composites parasitically causes thermal diffusions6-9, which limits printing resolution and surface roughness to sub-micron levels10-20 and thus impair their electrical and optical performances. Here, we develop thermoplasmonic laser printing (TPLP), a technique that transduces diffusive heat into a confining Coulombic potential to directly assemble metallic composites into 3D nanostructures. Unlike existing nanoprinting strategies10-15 where pulsed lasers with peak power up to 0.1 MW scale are required, our method can be operated using continuous-wave lasers at powers of 100 μW scale, which is 9 order-of-magnitude lower. We demonstrate 3D metal nanoprinting with finest feature size down to 86 nm, surface roughness as low as 1.6 nm and electrical conductivity up to 0.1×107 S/m, which are inaccessible by conventional methods. Our method opens a cost-efficient pathway to fabricate miniaturized 3D metallic devices for multifarious optoelectronic applications.</p>