4D Direct Laser Writing for Intelligent Micromachines

Intelligent micromachines are devices with sizes ranging from submillimeters to nanometers, capable of performing complex tasks adaptively at small scales. Smart micromachines have recently been developed that exhibit shape-morphing capability in response to various stimuli to adapt to their environment. However, for such micromachines to be effective in harsh environments, micromachines should be more than adaptive. Essentially, they must exhibit a high degree of intelligence, characterized by enhanced locomotion capability, self-adaptability, programmability, reconfigurability, and multifunctionality. 4D direct laser writing has enabled the rapid prototyping of stimulus-responsive adaptive micromechanisms and diverse functional microcomponents, including microscale sensors, actuators, data processors, memory structures, and power-supply structures. This review provides a comprehensive overview of the current state of the art in 4D microprinting technology based on two-photon polymerization for the intelligentization of micromachines. Further, it offers insights into the fabrication of intelligent micromachines via the integration of diverse functional components through the 4D direct laser writing technology.