Scientists develop "smart plastic" that changes its form from soft to hard in sunlight

They were inspired by living things, from trees to shellfish. Researchers at the University of Texas at Austin set their collective advanced minds on creating a plastic that would mimic real life. It would be like many life forms that are soft and stretchy in some places and hard and rigid in others.

Their success, a first ever, using only light and a catalyst to change the properties such as hardness and elasticity in molecules of the same type. The resulting material is ten times stronger than natural rubber and could very well change flexibility of electronics and robotics.

The findings were published recently in the journal Science.

"This is the first material of its type," said Zachariah Page, assistant professor of chemistry and corresponding author on the paper. "The ability to control crystallization, and therefore the physical properties of the material, with the application of light is potentially transformative for wearable electronics or actuators in soft robotics."

Background

In science, researchers have long studied the properties of living structures and wished to mimic them. Such living structures as skin and muscle, would then be made of synthetic materials. In living organisms. structures often mix attributes such as strength and flexibility with ease. When using a mix of synthetic materials to mimic these attributes, the materials often fail, coming apart and ripping at the meeting joint of different attributes.

"Oftentimes, when bringing materials together, particularly if they have very different mechanical properties, they want to come apart," Page said.

Page and the team at University of Texas at Austin were able to control and change the structure of a plastic-like material. They used light to alter how firm or stretchy the material would become.

The Process

Chemist used a monomer, which is a small molecule that binds with other like it to form building blocks for larger structures, called polymers. In this instance the polymers were similar to those found in most commonly used plastic.

It took about a dozen trials until a catalyst was found that when added to the monomer and then shown visible light, resulted in a semicrystalline polymer that is similar to that found in existing synthetic rubber. A harder more rigid material was formed in the areas that light touched, while the unlit areas properties stayed soft and stretchy.

In the resulting substance the attributes were exaggerated, because the substance is made of one material with different properties. It was stronger and could be stretched farther than most mixed materials.

The reaction takes place at room temperature, the monomer and catalyst are readily available on the market and the light source was simple blue LEDs, everything commercially available and inexpensive. In addition the reaction takes place in less then an hour, minimizing the use of hazardous waste, which makes the process rapid, inexpensive, energy efficient and environmentally benign.

The future of the study

The researchers are next focused on seeking more and different objects to develop with this material, to test its usability.

The team is envisioning a flexible material that can be used to anchor electronic components in such things as medical devices or other wearable tech. In robotic strong and flexible materials are desirable to improve movement and durability.