# Optofluidic three-dimensional microfabrication and nanofabrication

## TL;DR

A new method for 3D microfabrication uses light and fluid interactions to create complex structures from various materials, enabling advanced microdevices.

## Contribution

A universal 3D fabrication strategy using optofluidic interactions for assembling diverse nanoparticles into complex structures.

## Key findings

- The method enables fabrication of 3D microfluidic valves with size-selective sieving functionality.
- Microrobots with multimodal locomotion using four different functional materials were successfully created.
- The approach works with a wide range of materials including metals, metal oxides, and quantum dots.

## Abstract

Three-dimensional (3D) microfabrication/nanofabrication technologies have revolutionized various fields by enabling the precise construction of complex microstructures/nanostructures1–6. However, existing methods face challenges in fabricating intricate 3D architectures from a diverse range of materials beyond conventional polymers. Here we introduce a universal 3D microfabrication/nanofabrication strategy compatible with a broad range of materials by precisely manipulating optofluidic interactions within a confined 3D space, enabling the creation of volumetric, free-form 3D microstructures/nanostructures. A femtosecond-laser-induced heating spot generates a localized thermal gradient, providing precise spatiotemporal control over optofluidic interactions of the nanoparticle-laden dispersions. This enables the rapid and highly localized assembly of nanoparticles with diverse shapes and compositions—including metals, metal oxides, carbon nanomaterials and quantum dots—into complex 3D microstructures. To demonstrate its versatility, we fabricate multifunctional microdevices, such as 3D microfluidic valves with size-selective sieving functionality, achieving fast separation of microparticles/nanoparticles with distinct dimensions, as well as microrobots integrated with four distinct functional materials, achieving multimodal locomotion powered by different external stimuli. This optofluidic 3D microfabrication/nanofabrication method unlocks new opportunities for advanced material innovation and miniaturized device development, paving the way for broad applications in colloidal robotics7, microphotonics/nanophotonics, catalysis and microfluidics.

A strategy compatible with a broad range of materials by precisely manipulating optofluidic interactions within a confined 3D space to control the assembly of colloidal microparticles/nanoparticles is demonstrated, enabling the precise manufacture of complex microstructures/nanostructures.