As a micro-nano additive manufacturing (AM) technology, micro-nano 3D printing based on photopolymerization has significant advantages in the manufacture of high-precision and complex micro-nanostructures. Traditional AM technology is essential in printing macroscale structures. However, its printing accuracy is limited, and the difficulty of meeting the demanding requirements for printing accuracy in many micro-nano manufacturing fields has grown tremendously. For example, the printing accuracy of microfluidic chips in the biological field is on a microscale. In micro-nano optics, the period of photonic crystals requires printing accuracy to reach hundreds of nanometers. Additionally, 3D printing technology can manufacture high-precision and complex three-dimensional structures and has huge industrial application needs in micro-nano electromechanical systems, micro-nano photonic devices, micro-fluidic devices, biomedicine and tissue engineering, and new materials. Thus, research on micro-nano 3D printing technology has received widespread attention.

Recently, researchers have developed various types of micro-nano 3D printing technologies suitable for several materials (organic polymers, metals, glass, ceramics, biological materials, composite materials, etc.). Micro-stereolithography (single-photon absorption) and two-photon polymerization using photopolymerization are the most representative micro-nano-scale 3D printing technologies. Micro-nano 3D printing technology based on photopolymerization uses the continuous, pulsed laser or LED light as its energy source. The photopolymerization reaction process is controlled at the micro-nano scale to print and manufacture the micro-nano 3D structure. First, the optical micro-nano resolution of 3D printing mainly depends on the diffraction limit of the optical system, such as the Rayleigh criterion 0.61 λ/NA, where λ and NA are the wavelength of the light source and numerical aperture of the imaging system, respectively. Sub-micron resolution can be obtained using a light source with a shorter wavelength, such as the UV beam, and an objective lens with a higher NA. Additionally, the lithography resolution, which is far beyond the optical diffraction limit (below 100 nm) can be achieved using ultra-fast femtosecond pulse lasers to excite the nonlinear response of the material, such as two-photon or multiphoton absorption effect. Finally, most of the micro-nano 3D printing optical systems are sets of micro-imaging systems, and the lithography resolution is improved using the latest and frontier super-resolution micro-imaging technology. For example, by introducing super-resolution microscopy, stimulated emission depletion (STED), two-color non-degenerate two-photon absorption (ND-TPA), and other technologies, the lithography resolution can be increased to less than 10 nm.

Currently, micro-nano 3D printing is one of the most frontier advanced manufacturing fields in the world. In 2014, micro-nano 3D printing was listed in the top 10 disruptive innovations of the year by the Massachusetts Institute of Technology MIT Technology Review. With the rapid improvement of prototyping technology for printing accuracy, efficiency, and other performance requirements, plane projection 3D printing has developed rapidly recently. Compared with traditional micro stereolithography, plane projection 3D printing has advantages including accuracy, efficiency, and equipment cost-efficiency. In 2015, researchers from Carbon 3D and the University of North Carolina proposed a layer scanning-based manufacturing method, known as the continuous liquid interface production (CLIP), which increased the printing rate by about 100 times. Recently, the most disruptive and transformative ultra-high-precision surface projection stereolithography (PμSL) and femtosecond projection two-photon lithography (FP-TPL) technologies have been undergoing rapid development. These technologies can break through the inherent contradiction between the printing precision and size and can achieve high-precision, high-efficiency, large-size, and low-cost manufacturing.

This paper present an up-to-date review of the development history, trends, and latest research progress in high-resolution, large-scale micro-nano 3D printing technology, achieved by different photochemical principles and optical methods. The rapid development of micro-nano 3D printing technology has completely changed the manufacturing of arbitrarily designable 3D structures from macro- to microscale. Projecting 3D printing has become the most important and rapidly developing micro-nano 3D printing method due to its performance and cost-effectiveness. We systematically reviewed different principles of optical 3D printing technology, from one-photon absorption, two-photon absorption, super-resolution imaging-assisted one/two-photon absorption principle. Furthermore, we reviewed the performance of different optical 3D printing systems, from single-focus serial scanning, multi-focus parallel scanning, surface projection, layer scanning, and volume manufacturing. We focused on the contradiction between print throughput and print resolution. Additionally, we discussed specific challenges in manufacturing structures with sub-diffraction limit feature size and large-scale area. The projection of 3D printing technology has been continuously developed and improved through the combination of advanced microscope imaging methods, such as STED, light-sheet imaging, random access scanning, and computed tomography. These methods have been successfully applied to various 3D printing systems, effectively improving the demand for high-resolution printing of macroscale 3D structures. Finally, some new and innovative methods in the field of optics are the main driving force for developing of micro-nano 3D printing. The photopolymerization micro-nano 3D printing technology will become an essential technique in laser precision micromachining in the future, and promote the development of intelligent manufacturing by leaps and bounds.