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Issue 2, 2020
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Soft temperature-responsive microgels of complex shape in stop-flow lithography

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Stop-flow lithography (SFL) has emerged as a facile high-throughput fabrication method for μm-sized anisometric particles; yet, the fabrication of soft, anisometric microgels has not frequently been addressed in the literature. Furthermore, and to the best of the authors' knowledge, no soft, complex-shaped microgels with temperature-responsive behavior have been fabricated with this technology before. However, such microgels have tremendous potential as building blocks and actuating elements in rapidly developing fields, such as tissue engineering and additive manufacturing of soft polymeric building blocks, bio-hybrid materials, or soft micro-robotics. Given their great potential, we prove in this work that SFL is a viable method for the fabrication of soft, temperature-responsive, and complex-shaped microgels. The microgels, fabricated in this work, consist of poly(N-isopropylacrylamide) (pNIPAm), which is crosslinked with N,N′-methylenebis(acrylamide). The results confirm that the shape of the pNIPAm microgels is determined by the transparency mask, used in SFL. Furthermore, it is shown that, in order to realize stable microgels, a minimum threshold of crosslinker concentration of 2 wt% is required. Above this threshold, the stiffness of pNIPAm microgels can be deliberately altered by adjusting the concentration of the crosslinker. The fabricated pNIPAm microgels show the targeted temperature-responsive behavior. Within this context, temperature-dependent reversible swelling is confirmed, even for fractal-like geometries, such as micro snowflakes. Thus, these microgels provide the targeted unique combination of softness, shape complexity, and temperature responsiveness and increase the freedom of design for actuated building blocks.

Graphical abstract: Soft temperature-responsive microgels of complex shape in stop-flow lithography

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Article information

30 Jul 2019
22 Nov 2019
First published
26 Nov 2019

Lab Chip, 2020,20, 285-295
Article type

Soft temperature-responsive microgels of complex shape in stop-flow lithography

H. J. M. Wolff, J. Linkhorst, T. Göttlich, J. Savinsky, A. J. D. Krüger, L. de Laporte and M. Wessling, Lab Chip, 2020, 20, 285
DOI: 10.1039/C9LC00749K

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