Micro-nano 3D printing, more accurate and macroscopic

Schematic diagram of the light field distribution of the femtosecond laser directly writing inorganic nanostructures. (Courtesy of Zheng Meiling)

Femtosecond lasers are already well known for their use in ophthalmic surgery to treat myopia.

But it can do much more than that. As an effective three-dimensional micro-nano fine processing technology, femtosecond laser direct writing can realize the preparation of micro-small photonic devices in a variety of transparent optical materials.

Zheng Meiling’s team at the Bionic Intelligent Interface Science Center of the Institute of Physics and Chemistry of the Chinese Academy of Sciences recently published two related achievements in different journals in the early stage of work accumulation, promoting femtosecond laser direct writing technology to take another step forward.

Advanced Materials Technology: Biomimetic-responsive hydrogel micro-actuator

Published in the results of Advanced Materials Technology under the title of “Femtosecond Laser Micromachining pH Driven Three-dimensional Flycatcher Hydrogel Driver”, the team synthesized the stimulus-responsive photoresist precursor, and combined with the structural design, prepared a 4D stimulus-responsive hydrogel microstructure using femtosecond laser direct writing technology.

The application of hydrogel micro actuators in micromanipulation, microrobots, microfluidics, smart sensors and other fields is very important. However, there are still huge challenges to achieve precise preparation and controllable manipulation of hydrogel micro-actuators at the micro-nano scale.

By optimizing the femtosecond laser direct writing parameters and laser processing path, the authors obtained a 4D hydrogel microstructure with controllable response behavior by optimizing the femtosecond laser direct writing parameters and laser processing path. The crosslinking density of the local region of the hydrogel microstructure is adjusted by changing the laser processing parameters, resulting in a controllable pH response behavior with a deformation time as short as 1.2 seconds and a recovery time of 0.3 seconds.

On this basis, inspired by the flycatcher’s trapping behavior, the researchers designed and machined a biomimetic asymmetric hydrogel micro-actuator that, through pH triggering, achieved and adjusted its shape change, successfully captured single or multiple microparticles, and controlled simultaneous or sequential release of microparticles.

This result enables the preparation of smart hydrogel micro-actuators.

Nature-Communications: Lithography micromachining of 3D inorganic materials using near-infrared light

Another article published in Nature Communications, “Multiphoton 3D Lithography to Achieve λ/30 Inorganic Feature Sizes,” describes the progress made by the team and partners in the preparation of 3D inorganic nanostructures by femtosecond laser superdimination nanolithography.

Laser 3D printing technology is one of the important means to prepare three-dimensional inorganic microstructures, but when preparing inorganic microstructures, its characteristic size and processing resolution are limited by the material and optical diffraction limits, and it is difficult to achieve nanoscale preparation.

In this work, the research team used the nonlinear interaction of femtosecond laser and matter to achieve the femtosecond laser superdiffract nanolithography of inorganic photoresist hydrogen sesquisiloxane (HSQ) through the “avalanche ionization” effect caused by multiphoton absorption, breaking through the limitation of HSQ’s inability to use visible and near-infrared light for lithography micromachining proposed by previous people.

The author systematically studied the influence of processing parameters such as laser energy, scanning speed and scanning mode on feature size, and successfully obtained self-supporting 33nm and 26nm HSQ nanostructures by finely adjusting the processing parameters of the laser, realized the characteristic size of λ/30 (laser wavelength 1/30), and prepared 3D inorganic microstructures with excellent high temperature and solvent resistance properties, and constructed a variety of photonic microdevices and biomimetic microstructures based on inorganic nanostructures.

This work has laid a solid foundation for the study of novel inorganic nanodevices based on HSQ microstructures.

NanoFlash: A new way to realize the complex structure of micro-nano at different scales

3D printing on the micro-nano scale can achieve any three-dimensional and high accuracy, but speaking of the biggest regret of this technology so far, Zheng Meiling told China Science News, “There is almost no product made in the industry, because the efficiency of this technology to prepare large structure devices is very low.” This is also a current research direction of the team.

In an earlier work published by NanoFlection, “Maskless Optical Projection Nanolithography achieves λ/12 super-resolution and efficient cross-scale structural patterning”, they partially solved this pain point problem.

Zheng Meiling’s team and partners use ultrafast laser with a wavelength of 400 nanometers as the light source, use digital micromirror chips (DMD) to generate patterned light fields, develop maskless optical projection superdiffractive nanolithography technology, break through the limitation of optical diffraction limit, obtain only 1/12 (λ/12) of the laser wavelength of 32 nanometer lithography linewidth, and efficiently prepare a cross-scale micro-nano structure with hundreds of micron scales and nanoscales coexisting.

In addition, the patterned light field is generated by the DMD required for computer control changes, which conveniently realizes the preparation of a variety of cross-scale micro-nano structure patterns, and after simple repetition of the process, the batch preparation of diversified patterns can also be realized.

Maskless optical projection superdiflating nanolithography technology provides an efficient and convenient new technology path for the patterning of cross-scale micro-nano complex structures, and is expected to be widely used in the research and development of micro and nano devices involving electronics, optics and biology, and to realize the low-cost, high-efficiency and mass manufacturing of customized micro-nano structures and devices. Journal reviewers described the technology as “truly groundbreaking.” (Source: China Science Daily Zhang Nan)

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