New Research Realizes Femtosecond Laser Processing Of Multi-joint Micromachines

Wu Dong's team, a professor at the Micro and Nano Engineering Laboratory of the University of Science and Technology of China (USTC), proposed a processing strategy of femtosecond laser 2-in-1 writing of multi-materials to fabricate micro-mechanical joints consisting of temperature-sensitive hydrogels and metal nanoparticles, and subsequently developed multi-jointed humanoid micro-machines with multiple deformation modes (＞10). The relevant research results have been published in Nature Communications.
In recent years, femtosecond laser two-photon polymerization technology has been widely used to fabricate microstructures with various functions as a true three-dimensional processing method with nanometer precision. These microstructures show promising applications in the fields of micro- and nano-optics, microsensors, and micro-machine systems. However, it is still challenging to realize composite multi-material processing with femtosecond lasers and further construct micro-nano-machines with multi-modalities.
Femtosecond laser two-in-one processing strategies include the construction of hydrogel joints using asymmetric two-photon polymerization and the laser reduction deposition of silver nanoparticles in localized regions of the joints. In particular, asymmetric photopolymerization creates anisotropy in the crosslink density in the local region of the hydrogel microjoint, which ultimately allows for directionally and angularly controllable bending deformations. In situ laser reductive deposition allows precise processing of silver nanoparticles on hydrogel joints. These silver nanoparticles have a strong photothermal conversion effect, enabling the mode switching of the multi-joint micromachines to exhibit an ultra-short response time (30 ms) and ultra-low driving power (<10 mW).
As a typical example, eight micro-joints were integrated on a humanoid micromachine. The researchers then utilized spatial light modulation to achieve a multifocal beam in 3D space, which in turn precisely stimulated each microjoint. The synergistic deformation between multiple joints prompted the humanoid micromachine to perform multiple reconfigurable deformation modes. Ultimately, the humanoid micromachine "dances" at the micrometer scale.
In the proof-of-concept, by designing the distribution and deformation direction of the micro-joints, the two-jointed micromanipulator can collect multiple micro-particles in the same and different directions. In summary, the femtosecond laser two-in-one processing strategy can construct deformable micro-joints in the local region of various 3D micro-structures, realizing multiple reconfigurable deformation modes.
According to the researchers, micromanipulators with multiple deformation modes will show promising applications in microgoods collection, microfluidic manipulation and cell manipulation.