Amphibious Hybrid\nLaser Tweezers for Fluid and Solid\nDomains

Optical trapping is a potent tool\nfor achieving precise\nand noninvasive\nmanipulation of small objects in a vacuum and liquids. However, due\nto the substantial disparity between optical forces and interfacial\nadhesion, target objects should be suspended in fluid environments,\nrendering solid contact surfaces a restricted area for conventional\noptical tweezers. In this work, by relying on a single continuous\nwave (CW) laser, we demonstrate an optical manipulation system applicable\nfor both fluid and solid domains, namely, amphibious hybrid laser\ntweezers. The key to our system lies in modulating the intensity of\nthe CW laser with duration shorter than the dynamic thermal equilibrium\ntime within objects, wherein strong thermal gradient forces with ∼6\norders of magnitude higher than the forces in optical tweezers are\nproduced, enabling moving and trapping micro/nano-objects on solid\ninterfaces. Thereby, CW laser-based optical tweezers and pulsed laser-based\nphotothermal shock tweezers are seamlessly fused with the advantages\nof cost-effectiveness and simplicity. Our concept breaks the stereotype\nthat CW lasers are limited to generating tiny forces and instead achieve\nultrawide force generation spanning from femto-newtons (10<sup>–15</sup> N) to (10<sup>–6</sup> N). Our work expands the horizon\nof optical manipulation by seamlessly bridging its applications in\nfluid and solid environments and holds promise for inspiring optical\nmanipulation techniques to perform more challenging tasks, which may\nunearth application scenarios in diverse fields such as fundamental\nphysical research, nanofabrication, micro/nanorobotics, biomedicine,\nand cytology.