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Femtosecond laser micromachining technique spawns "dancing" robots

Final robot

Made up of eight micro-joints stimulated by multi-focal beams in 3D space, these machines were able to achieve a number of deformation modes – leading to “dancing” microrobots at the micrometre scale. (Image: The University of Science and Technology of China)

A method of using femtosecond lasers to create micromachined joints has been introduced by researchers – demonstrated by “dancing” humanoid micro-robots.

Researchers from the University of Science and Technology of China (USTC) of the Chinese Academy of Science proposed a femtosecond laser 2-in-1 writing multi-material processing strategy to create micromachined joints made of temperature-sensitive hydrogels and metal nanoparticles. 

In future, USTC says, micromachinery with various deformation modes could hold promise for applications such as micro-goods collection, microfluidic manipulation, and cellular operations.

To demonstrate their method, the team built multi-jointed humanoid micromachines with multiple deformation modes. Made up of eight micro-joints stimulated by multi-focal beams in 3D space, these machines were able to achieve a number of deformation modes – leading to “dancing” microrobots at the micrometre scale, USTC says. 

All the robots

The design and fabrication of light-triggered multi-joint microactuators by two-in-one laser printing. (Image: The University of Science and Technology of China)

The femtosecond laser dual-function fabrication strategy, detailed in Nature Communications, involves using asymmetric two-photon polymerisation to create hydrogel joints and locally depositing silver nanoparticles via laser reduction within the joints. This asymmetric light-polymerisation technique induces anisotropy in cross-linking density within specific areas of the hydrogel micro-joints, enabling directional and angular-controllable bending deformations. 

The in-situ laser reduction deposition allows for the precise fabrication of silver nanoparticles on the hydrogel joints. These nanoparticles exhibit strong photothermal conversion effects, enabling the multi-joint micromachinery to showcase ultra-fast response times (30 ms) and extremely low driving power (<10 mW) characteristics.

Femtosecond laser two-photon polymerisation, as a true 3D fabrication technique with nanoscale precision, can produce various functional microstructures, which hold promise for micro-nano optics, microsensors, and microelectromechanical systems, USTC says.

However, it adds, the challenge remains in using femtosecond lasers for multi-material processing and constructing micro-nano mechanics with multi-modalities.

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