A new paper in Nature describes the US-Army-funded research of U Penn materials scientists to create a new generation of 3D printed "smart objects" whose geometry and materials enable them to interact with their environments without having to use embedded computers, sensors or actuators.
The researchers are combining two techniques here: the first is the geometric technique of creating bistable structures that can hold either of two configurations indefinitely and can freely shift from one to the other.
The second is the precise use of materials in these bistable structures that expand or contract in the presence of different substances or pressures — water, oil, light, heat, etc.
By combining these techniques, the researchers created "embodied logic": objects that physically alter their shapes based on environmental conditions. These objects can be made at very small scales, giving them lots of applications in microfluidics.
Changing the beams' starting length/width ratio, as well as the concentration of the stiff internal fibers, allows the researchers to produce actuators with different levels of sensitivity. And because the researchers' 3D-printing technique allows for the use of different materials in the same print, a structure can have multiple shape-changing responses in different areas, or even arranged in a sequence.
"For example," Jiang says, "we demonstrated sequential logic by designing a box that, after exposure to a suitable solvent, can autonomously open and then close after a predefined time. We also designed an artificial Venus flytrap that can close only if a mechanical load is applied within a designated time interval, and a box that only opens if both oil and water are present."
Bifurcation-based embodied logic and autonomous actuation [Yijie Jiang, Lucia M. Korpas & Jordan R. Raney/Nature]
Engineers 3D print smart objects with 'embodied logic [Science Daily]