Polymer Robot Responds, Changes Form Based on Humidity


A soft robot. / Photo by: Hdehqani via Wikimedia Commons


Common robots that can be operating in the air, on land, and under the sea are mostly hard and robust. Although these tough machines are capable of using multiple electronic components, they lack the ability to mimic traits of organisms, like adaptability. Researchers at Wright-Patterson Air Force Base developed soft robots that change form according to stimuli and may be used in biomedical applications.

The researchers observed octopuses and their nervous system distributed in their boneless limbs. They used the animal’s form as an inspiration to build a soft robot made of a folded sheet of polypropylene, a thermoplastic polymer that reacts with humidity. The environmental signal caused by the changes in air humidity is translated by the robot as a mechanical signal, allowing it to assume a different shape. In addition to that, the polymer can absorb water without losing its structure, unlike with paper. The material would make the robot swell as humidity rises and shrink as humidity goes down.

“For approximately the last decade we have been interested in responsive materials such as artificial muscles and actuators. It is the combination of form and design that leads to optimal function,” said Dr. Richard Vaia, the lead author of the study and Technical Director of the Functional Materials Division at the Air Force Research Laboratory at Wright-Patterson.

Since the polymer can change its shape, the researchers also noted that the soft robot has origami-like mechanical logic, while responsiveness of the material is a potential property applicable to many aspects of biomedicine. The thermoplastic polymer may be applied in human rehabilitation or surgical intervention. Also, the flexibility and reactivity of the polymer may lead to the creation of robots that have light, elastic forms.