Complex functional materials with three-dimensional micro- or nano-scale dynamic compositional features are prevalent in nature. However, the generation of three-dimensional functional materials composed of both soft and rigid microstructures, each programmed by shape and composition, is still an unsolved challenge. Here we describe a method to code complex materials in three-dimensions with tunable structural, morphological and chemical features using an untethered magnetic micro-robot remotely controlled by magnetic fields. This strategy allows the micro-robot to be introduced to arbitrary microfluidic environments for remote two- and three-dimensional manipulation. We demonstrate the coding of soft hydrogels, rigid copper bars, polystyrene beads and silicon chiplets into three-dimensional heterogeneous structures. We also use coded microstructures for bottom-up tissue engineering by generating cell-encapsulating constructs.
We thank H.I. Gungordu for her help in MTT assays and S. Chung, X. Dong and J. Giltinan for their help in preparing magnetic micro-robot experiments. U.D. acknowledges that this material is based in part on work supported by the National Science Foundation under NSF CAREER Award Number 1150733, NIH R21HL112114 and NIH R01EB015776-01A1. M.S. and E.D. were partially supported by the National Science Foundation under NSF-NRI Award Number 1317477. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. U.D. is a founder of, and has an equity interest in, DxNow Inc., a company that is developing microfluidic and imaging technologies for point-of-care diagnostic solutions. U.D.’s interests were reviewed and are managed by the Brigham and Women’s Hospital and Partners HealthCare in accordance with their conflict of interest policies.
Two-dimensional micro-robotic coding and reconfiguration of PEG hydrogels with various shapes into complex planar constructs. Scale bar is 1 mm.
Two-dimensional micro-robotic coding of material composition. Square hydrogels were surrounded by bracket-shape hydrogels. Scale bar is 1 mm.
Orientation and position control in untethered micro-robotic coding of material composition. “Tetris”-shaped PEG hydrogels were assembled in a rectangular reservoir. Scale bar is 1 mm.
Three-dimensional micro-robotic coding of a heterogeneous structure consisting of PEG microgels which totally encase 100 μm diameter copper cylinders and 200 μm diameter polystyrene spheres. The experiment was performed in a 20 mm x 20 mm x 4 mm chamber in PBS. Scale bar is 1 mm.