Soft robots utilize humidity gradient levels to generate signals

Autonomously reconfiguring origami units can be connected to form dynamic Boolean logic gates. For example, the state of the gate reconfiguration of an input (right) can change the shape of the output (bottom). Credit: PNAS

A team of researchers at the U.S. Air Force Research Laboratory, Wright-Patterson Air Force Base, has developed a type of soft robot that can generate signals without using electricity.

In their paper published in Proceedings of the National Academy of Sciences, the researchers describe their study of origami objects and their possible use as signaling devices and possibly as logic gates.

Origami is, of course, the art of folding paper into interesting objects. In this new effort, the researchers looked to the ancient art form as a possible building block for a soft robot. Instead of using paper, the team used sheets of polypropylene—it can absorb water from atmospheric humidity without losing its main form.

It does lose some of its stiffness, however, when put into a humid environment. The researchers exploited that phenomenon to use such sheets as mechanical actuators.

They found that if they bent the sheets in certain places, the sheet would flatten when exposed to humid conditions. Conversely, the sheets would rise once again when exposed to drier air.

This ability to move between states, the researchers noted, allowed the sheets to serve as a trigger for actions by other types of devices or machines.

It also allowed for the generation of signals using only environmental conditions—based on the way the polypropylene behaved over a humidity gradient.

And under the right conditions, the sheets could exist in two states, flat or upright, suggesting their use as logic gates.

Soft robots utilize humidity gradient levels to generate signals
Autonomous reconfiguration of origami powered by the environment leads to crawling locomotion. Credit: PNAS

In testing their ideas, the researchers found that when joining several sheets together, they could share information, carry out Boolean logic and even move around.

This, they claim, suggests their use in wide variety of soft-robot applications, some of which might include carrying out functions normally done by digitally based machines.

Soft robotics is a promising field due to some of the expected benefits. Such robots would be better, it is believed, at handling delicate objects.

Soft robots that could carry out tasks automatically are expected to offer services such as signaling air conditioning systems or manipulating objects based on nothing but humidity levels.

Crawling locomotion of an environmentally responsive waterbomb. Energy stored mechanically in the waterbomb is released during snap-through causing the structure to jump forward. Credit: Proceedings of the National Academy of Sciences (2018). DOI: 10.1073/pnas.1805122115

More information: Benjamin Treml et al. Origami mechanologic, Proceedings of the National Academy of Sciences (2018). DOI: 10.1073/pnas.1805122115


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