Georgia Tech, USA
Dr. H. Jerry Qi is Professor and the Woodruff Faculty Fellow in the School of Mechanical Engineering at Georgia Institute of Technology. He received his doctoral degree from MIT in 2003. He joined University of Colorado Boulder as an assistant professor in 2004 and moved to Georgia Tech in 2014. Prof. Qi's research is in the broad field of nonlinear mechanics of active polymers. He and his collaborators have been working on a range of active polymers, including shape memory polymers, light activated polymers, covalent adaptable network polymers, for their interesting behaviors such as shape memory, light actuation, surface patterning, surface welding, healing, and reprocessing. In recent years, he has been working on investigating integrating active materials with 3D printing. He and his collaborators pioneered the 4D printing concept. Prof. Qi is a recipient of NSF CAREER award (2007) and was elected to an ASME Fellow.
Multimaterial Additive Manufacturing for Printed Active Composites
3D printing (additive manufacturing) where materials are deposited in a layer-by-layer manner to form a 3D solid has seen significant advances in recent decades. 3D printing has the advantage of creating a part with complex geometry from a digit file, making them an ideal candidate for making architected materials. Multimaterial 3D printing is an emerging field in recent years in additive manufacturing. It offers the advantage of the placement of materials with different properties in the 3D space with high resolution, or controllable heterogeneity. It also provides new opportunities to create a new class of composites, active composites, where active materials are used together with non-active materials to fabricate a composite that can intelligently respond to environmental stimuli, such as temperature, pH, etc. In this talk, we present our work in using additive manufacturing, in particular, multimaterial additive manufacturing, to fabricate active composites. We start by using a commercial polyjet 3D printer, in which one of the materials is a shape memory polymer. Through careful design of spatial distribution of active and non-active materials, we are able to create active composites that can change their shape upon environmental stimuli, such as temperature (Fig. 1). We then present a new development of a novel multi-material multi-method (m4) 3D printing where we integrate four types of additive manufacturing methods and two complementary methods into one platform. This highly integrated multi-material hybrid printing system allows us to integrate materials of dramatically different properties, such as polymers, liquid crystal elastomers, and conductive materials into one composite, and thus enables unprecedented functionalities. Finally, the future challenge of additive manufacturing for active composites will be discussed.
Figure 1: Printed active composites: an expanding lattice. a) Both active and non-active materials are used. b) The as-printed lattice. c) It expands upon heating. d) The fully expanded lattice.
 Q. Ge, H.J. Qi, and M.L. Dunn, Active materials by four-dimension printing. Applied Physics Letters, 2013. 103: p. 131901.
 Z. Ding, C. Yuan, X. Peng, T. Wang, H.J. Qi, and M.L. Dunn, Direct 4D printing via active composite materials. Science Advances, 2017. 3(4).
 D.J. Roach, C.M. Hamel, C.K. Dunn, M.V. Johnson, X. Kuang, and H.J. Qi, The m4 3D printer: A multi-material multi-method additive manufacturing platform for future 3D printed structures. Additive Manufacturing, 2019. 29: p. 100819.