Significance  Femtosecond laser refers to the pulse duration in the femtosecond scale (10^-15 seconds), with ultra-short pulse, long wavelength, ultra-high peak power and nonlinear absorption effect. During processing, the femtosecond laser with high energy density acts on the surface of the material after focusing, and has a nonlinear absorption effect on the substance, which can realize the molding, modification or removal of the material, so as to achieve fine processing. Femtosecond laser processing technology has micro and nano-scale processing resolution and three-dimensional manufacturing capability, which can manufacture microrobots with specific shapes and sizes. The prepared microrobot can perform various tasks at the microscopic scale, has the advantages of small size, light weight and low energy consumption, and can shuttle in various environments, and achieve the effect of targeted therapy without harming the human body. In the future, with the continuous development and improvement of femtosecond laser technology, microrobots are expected to play an important role in more key areas, providing entirely new solutions to solve complex scientific and engineering problems.

Progress  First of all, the femtosecond laser polymerization processing micro-nano robot technology is based on the two-photon absorption effect, that is, the monomer molecule absorbs the free radical generated by two photons at the same time, and then carries out a complex polymerization reaction to form a polymer solid macromolecule, and finally obtains the three-dimensional micro-nano robot structure through development. According to whether the prepared micro-nano robot can be deformed, it can be divided into hard micro-nano robot and soft micro-nano robot. The rigid micro-nano robot has the advantages of large output force, high speed and high precision. The soft micro-nano robot can change its shape and size according to the needs of the environment and adapt to work in a complex environment.

　　The materials used for femtosecond laser processing of micro-nano robots are mainly responsive hydrogels, photoresist and metals. Hydrogels have the characteristics of good expansibility, strong water absorption, easy water retention, ultra-bionic, etc. The processed micro and nano robots can make regular structure and volume adjustment according to the changes of environmental temperature, pH, light, electric field, magnetic field, etc., and change the gel state and composition, which has high intelligent response characteristics. Due to the excellent strength and hardness of metal materials, it makes microrobots have a strong structure and stable performance, ensuring stable operation in a variety of environments. Photoresist has shown excellent performance in the preparation of microrobots, which can not only achieve fine processing at the micro-nano scale, but also make microrobots highly customizable in structure and function due to their unique photosensitizing properties. The use of photoresist makes the design and manufacturing process of microrobots more flexible, and the structural design of microrobots can be quickly adjusted and optimized according to different application requirements. Metal materials have excellent electrical and thermal conductivity, which is crucial for the energy supply and heat dissipation of microrobots, they can efficiently transmit electrical energy to ensure the power supply of microrobots, while effectively dissipating the heat generated in the movement of microrobots to avoid overheating damage.

　　In addition, with the development of multi-functional 3D microrobots, the application of microrobots has been widely concerned by researchers. Due to their micron-scale size, in the biomedical field, the main applications of microrobots include targeted drug delivery, cell manipulation and minimally invasive surgery. In industry, microrobots are mainly used in the micro-machining of precision devices and the detection of micro-objects.

Conclusions and Prospects  Because of its high precision, high efficiency and controllability, laser micro-nano machining technology provides a powerful tool for the design and manufacture of medical micro-robots. This technology can achieve precise control of micro-scale materials, and provides a key support for miniaturization, multi-function and intelligence of medical microrobots. Laser micro-nano processing technology, with its unparalleled accuracy and flexibility, is quietly changing the manufacturing and application pattern of micro-robots, not only promoting the rapid development of the field of micro-robots, but also laying a solid road for its wide application in many fields such as medicine, biology, materials science and so on.