Manufacturing "living" 3D structures Christoph A. Spiegel 1,2 , H.B. Duc Tran 1,2 , Y. Jia 3 , W. Wenzel 4 , M. Tsotsalas 3 , Eva Blasco 1,2 1 Institute for Molecular Systems Engineering and Advanced Materials, Heidelberg University, Germany 2 Institute of Organic Chemistry, Heidelberg University, Germany
3 Institute of Functional Interfaces, Karlsruhe Institute of Technology, Germany 4 Institute of Nanotechnology, Karlsruhe Institute of Technology, Germany
Manufacturing of 3D complex structures featuring the ability to adapt on-demand similarly to living systems in Nature is highly desired for many applications such as microrobotics or -fluidics. Such features can be obtained by the introduction of dynamic chemistry in printable materials. Dynamic bonds can be broken and reformed under certain conditions and can provide unprecedented “livingness” to the printed structures. Here, we present a novel ink system permitting the fabrication of mechanical adaptable microstructures by combining two-photon laser printing with dynamic and living characteristics of the alkoxyamine bond. We designed a PEG-DA based ink formulation including a methacrylate-functionalized nitroxide radical source, allowing the formation of alkoxyamine bonds during microstructure fabrication. 1 Afterwards, alkoxyamine reactivity was exploited, rendering structures softer by crosslinking reduction via nitroxide exchange reaction (NER) or stiffer by nitroxide mediated polymerization (NMP) incorporating polystyrene. Herein, by post-printing modification via NER and NMP, the mechanical properties such as Young’s modulus or hardness as well as the size of the micro objects were fine-tuned on demand. For example, chain extension via NMP resulted not only in a remarkable increase of the Young's Modulus about two orders of magnitude (from 14 MPa to 3 GPa), but also in an impressive growth in structural size (8-fold), while preserving the overall initial 3D shape and even finest structural details (see figure). Thus, our approach providing access to microstructures being tunable in size and mechanical properties offers tremendous applicability in areas where customized structures are necessary.
References 1. Jia, Y.;Spiegel, C. A.;Welle, A.;Heißler, S.;Sedghamiz, E.;Liu, M.;Wenzel, W.;Hackner, M.;Spatz, J. P.;Tsotsalas, M.;Blasco, E.; Adv. Funct. Mater. 2022 , 2207826.
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