Stop-Flow Lithography for the Continuous Production of Degradable Hydrogel Achiral Crescent Microswimmers

Abstract

The small size of robotic microswimmers makes them suitable for performing biomedical tasks in tiny, enclosed spaces. Considering the effects of potentially long-term retention of microswimmers in biological tissues and the environment, the degradability of microswimmers has become one of the pressing issues in this field. While degradable hydrogel was successfully used to prepare microswimmers in previous reports, most hydrogel microswimmers could only be fabricated using two-photon polymerization (TPP) due to their 3D structures, resulting in costly robotic microswimmers solution. This limits the potential of hydrogel microswimmers to be used in applications where a large number of microswimmers are needed. Here, we proposed a new type of preparation method for degradable hydrogel achiral crescent microswimmers using a custom-built stop-flow lithography (SFL) setup. The degradability of the hydrogel crescent microswimmers was quantitatively analyzed, and the degradation rate in sodium hydroxide solution (NaOH) of different concentrations was investigated. Cytotoxicity assays showed the hydrogel crescent microswimmers had good biocompatibility. The hydrogel crescent microswimmers were magnetically actuated using a 3D Helmholtz coil system and were able to obtain a swimming efficiency on par with previously reported microswimmers. The results herein demonstrated the potential for the degradable hydrogel achiral microswimmers to become a candidate for microscale applications.

Magnetically-actuated hydrogel-based achiral planar microswimmers for SERS detection: In situ coprecipitation for continuous loading of iron oxide nanoparticles

“…With the development of micro- and nanofabrication technologies, many viable techniques can be used to fabricate microswimmers, such as biotemplating synthesis ( Zhang et al, 2009 ; Schuerle et al, 2012 ; Gao et al, 2014 ; Ali et al, 2017 ), chemical synthesis ( Cheang et al, 2017 ), lithography ( Chen et al, 2021 ; Mu et al, 2021 ; Xiong et al, 2022 ), and 3D printing ( Wang et al, 2018 ; Dong et al, 2020 ; Lee et al, 2021 ; Park et al, 2021 ). Among these techniques, ultraviolet lithography (UVL) and thin-film deposition technologies demonstrated the advantages of using parallel batch fabrication to achieve high efficiency, high consistency, and low-cost manufacturing of microswimmers ( Zhang et al, 2009 ; Huang et al, 2016 ; Go et al, 2018 ; Tottori and Nelson, 2018 ; Xu et al, 2019 ; Mu et al, 2021 ).…”