Engineers from the University of Pennsylvania’s School of Engineering and Applied Science (SEAS) have created bioinspired 3D printed structures that move and react to its environment.
Such objects do not require electronically-integrated systems, but, much like the venus fly trap, uses atmospheric stimuli to operate; the University of Pennsylvania team have dubbed this as “embodied logic”. The researchers published their study in the journal Nature Communications.
“Inspired by nature, we embody logic in autonomous systems to enable them to respond to multiple stimuli,” the study states.
“Using 3D printable fibrous composites, we fabricate structures with geometries near bifurcation points [where an object splits]. When suitable stimuli are present, the materials swell. This forces a key geometric parameter to pass through a bifurcation, triggering rapid and large-amplitude self-actuation.”
The following clip from the University of Pennsylvania displays a 3D printed venus flytrap which only closes when weight is inside and the actuator is exposed to a solvent.
3D printed bistable lattices
According to Jordan Raney, an assistant professor in Penn Engineering’s Department of Mechanical Engineering and Applied Mechanics, and leader of this research, “Bistability is determined by geometry, whereas responsiveness comes out of the material’s chemical properties.”
“Our approach uses multi-material 3D printing to bridge across these separate fields so that we can harness material responsiveness to change our structures’ geometric parameters in just the right ways.”
The team created active structures with “gates” that can be controlled by simple changes in the environment. These gates contained non-electric actuators. With a lattice formation, the polydimethylsiloxane (PDMS)-based and hydrogel-based structures, maintain elastic energy for kinetic movement. PDMS is a silicon-based organic polymer. Furthermore, the team used water and oil-based solvents, to activate the 3D printed structures.
“[This] could be useful for applications in microfluidics,” added Raney.
“Rather than using a solid-state sensor and microprocessor that are constantly reading what’s flowing into a microfluidic chip, we could, for example, design a gate that shuts automatically if it detects a certain contaminant.”
4D printing with shape-changing materials
Shaping-changing have been used in additive manufacturing to create 3D printed moving objects, i,e, 4D printing. Recently, Nicole Hone, an industrial design Master’s student at the Victoria University of Wellington, New Zealand, designed several 4D printed interactive plants using multi-material 3D printing and elastopolymer composites.
Prior to this, researchers from the University of Bristol and University of Bath, created a 4D printed smart material from 3D printed ink that harnesses cellulose fibers to transform in response to water.
The study, “Bifurcation-based embodied logic and autonomous actuation,” was co-authored by Yijie Jiang, Lucia M. Korpas, and Jordan R. Raney.
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Featured image shows an embodied logic actuator releasing its elastic energy. Clip via the University of Pennsylvania.