China University of Science and Technology realizes femtosecond laser processing of multi-joint micromachines

The team of Wu Dong, a professor at the Micro-Nano Engineering Laboratory of the University of Science and Technology of China, proposed a processing strategy for femtosecond laser two-in-one writing multi-materials, fabricated micromechanical joints composed of temperature-sensitive hydrogels and metal nanoparticles, and then developed a multi-joint humanoid micromachine with multiple deformation modes (>10). The results of the study were recently published in Nature Communications.

Inspired by human multi-joint deformation, the femtosecond laser two-in-one multi-material processing strategy was used to construct a multi-joint humanoid micromachine. Photo courtesy of China University of Science and Technology

In recent years, femtosecond laser two-photon polymerization technology, as a true three-dimensional processing method with nanometer precision, has been widely used to manufacture various functional microstructures, which have shown broad application prospects in the fields of micro-nano optics, microsensors and micro-machine systems. However, how to use femtosecond laser to realize composite multi-material processing and further construct micro-nano machinery with multi-modality is still extremely challenging.   

Femtosecond laser 2-in-1 processing strategies include the construction of hydrogel joints using asymmetric two-photon polymerization and laser reduction of deposited silver nanoparticles in local areas of the joint. Among them, the asymmetric photopolymerization technology makes the cross-linking density in the local area of the hydrogel micro-joint anisotropic, and finally enables it to achieve controllable bending deformation in direction and angle. In situ laser reduction deposition can precisely process silver nanoparticles on hydrogel joints, which have strong photothermal conversion effects, so that the modal switching of multi-joint micromachines exhibits excellent characteristics of ultra-short response time (30 ms) and ultra-low drive power (< 10 mW).                            

As a typical example, eight microjoints are integrated on a humanoid micromachine. Spatial light modulation is then used to achieve a multifocal beam in 3D space to precisely stimulate each microjoint. The co-deformation between multiple joints prompts the humanoid micromanipulator to complete multiple reconfigurable deformation modes. Finally, “dancing microrobots” were realized at the micron scale.

Finally, as a proof of concept, by designing the distribution and deformation direction of microjoints, the bi-joint micro-robotic arm can collect multiple microparticles in the same and opposite directions. In short, the femtosecond laser two-in-one processing strategy can construct deformable microjoints in various local areas of three-dimensional microstructures, and realize a variety of reconfigurable deformation modes.

According to the researchers, in the future, micromanipulators with a variety of deformation modes will show broad application prospects in micro-cargo collection, microfluidic manipulation and cell manipulation. (Source: Wang Min, China Science News)                          

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