Diffusiophoretic Trapping and Assembly of Nanoparticles Enhanced by Multilayer MXene Nanosheet

Efficient manipulation of nanoscale multiple colloids poses great challenges on laser power, flexibility, and photodamage. MXene, as an emergent 2D material, exhibits excellent optothermal and mechanical properties when coated on various substrates. Herein, a novel optothermal manipulation platform based on multilayered MXene nanosheets is proposed, with great cell compatibility. The experimental and theoretical results demonstrate that individual multilayered MXene nanosheets exhibit superb photothermal conversion efficiency at visible wavelengths. The 500 nm-diameter colloidal particle can be stably trapped and transported under a power of 0.6 mW, which is over two orders of magnitude smaller than traditional optical tweezers. Specifically, a reversible self-assembly of colloidal particles with diverse patterns, including hexagonal crystallization, chain pattern, and ring-shaped assembly. This is realized by control over the laser-induced temperature gradient and thermophoretic response. Furthermore, a single-flake level MXene can also closely adhere to the cell membrane, in addition to glass substrates. This enables directed migration and assembly of a large number of particles on a cellular substrate. Compared with a typical noble metal substrate, MXene has better biocompatibility, flexibility, and without the need for complex micro-nano fabrication processes. It is expected to promote applications in biomolecular interactions, cellular drug delivery, and colloidal crystals.