image: (a) The rapid fabricating method of pH-responsive helical structure. The helix is polymerized by the rotary holographic ring beam (RHRB) combined with the sample’s translation. The circular arrows denote the rotation direction of RCGH and RHRB, and the straight arrow represents the moving direction of the sample. (b) The generation of RCGH is composed of a CGH and a RLPM. (c) The schematic diagram of the holographic femtosecond laser processing system to fabricate microhelix. (d) Diagrammatic sketch of the expansion and contraction of the pH-triggered hydrogel-based helix. (e) The shrinking/swelling mechanism of pH-responsive hydrogel. The upper row is the schematic mechanism of the expansion and contraction of pH-responsive hydrogels. The bottom row denotes the SEM images of the hydrogel porosities in contracted (left) and expanded (right) states. Scale bar: 500 nm. (f) Schematic diagrams of various microorganisms in nature and optical images of corresponding biomimetic microhelices fabricated by the RHRB in one step. Scale bar: 25 μm.
Credit: by Rui Li, Yuan Tao, Jiawen Li, Dongdong Jin, Chen Xin, Shengyun Ji, Chaowei Wang, Yachao Zhang, Yanlei Hu, Dong Wu, Li Zhang and Jiaru Chu.
Microorganisms, such as bacteria and sperm, can undergo adaptive shape morphing to optimize their locomotion mechanisms in the environment, which enables them to navigate complex barriers and improve survival. Inspired by this autonomous behavior, artificial reconfigurable microrobots have been proposed to realize similar adaptation capabilities.
Helical microswimmers are particularly promising for biomedical applications because of their unique propulsion mechanism. Under a rotating magnetic field, helical microswimmers can transition dynamically between tumbling and corkscrewing motions, allowing them to navigate complex terrain and achieve targeted drug delivery.
In a new paper published in Light: Applied Manufacturing, a team led by Professor Jiawen Li from the University of Science and Technology of China has developed new ways to make helical microswimmers that are very small, with dimensions in the micrometer range. This is important because many biological structures, such as cells, capillaries, and wrinkles on cell surfaces, are also very small.
Microscale helical microswimmers are promising tools for biomedical applications, such as drug delivery and targeted therapy. However, some challenges still need to be addressed before these microswimmers can be widely used in clinical practice.
One challenge is the fabrication of microscale helical microswimmers. Femtosecond direct laser writing (fs-DLW) is a powerful tool for fabricating complex 3D structures with high resolution, but it is a slow and inefficient process. This makes it difficult to produce large quantities of microswimmers quickly.
Another challenge is the adaptive locomotion of microswimmers in complex environments. Inside the body, pH values vary among different tissues, and numerous microchannels and obstacles exist. Microswimmers need to be able to sense their environment and adapt their locomotion accordingly to reach their target destination.
Researchers are addressing these challenges. One approach is to develop new fabrication methods that are more efficient and scalable than fs-DLW. Another approach is to design microswimmers that are more responsive to environmental stimuli and can adapt their locomotion accordingly.
In this study, researchers developed a new method for fabricating pH-responsive helical hydrogel microswimmers. This method is called rotary holographic processing and is much faster than traditional methods. It can produce microswimmers in less than a second, approximately one hundred times faster than the point-by-point scanning strategy.
The microswimmers are made of hydrogel, which is a type of material that can absorb water. This makes the microswimmers responsive to pH changes. When the pH of the surrounding environment changes, the microswimmers change shape. This shape change allows the microswimmers to move in different ways.
Under a constant rotating magnetic field, the microswimmers can tumble or corkscrew. The type of motion depends on the pH of the environment. In a low pH environment, the microswimmers contract and tumble. In a high pH environment, the microswimmers expand and corkscrew.
The researchers assessed the microswimmers in various conditions and found that they could traverse complex terrains and deliver drugs to targeted cells. This suggests that rotary holographic processing is a promising method for fabricating microswimmers for biomedical applications.
This research suggests that rotary holographic processing is a promising new method for fabricating microswimmers for biomedical applications. The microswimmers are fast, reconfigurable, and able to navigate complex environments. This makes them ideal for targeted drug delivery and cell therapy tasks.
Journal
Light: Advanced Manufacturing