Imagine drawing a simple circuit on a plastic sheet, heating it up, and watching it shrink into a tiny, perfectly shaped electronic device that can stick to a finger, wrap around a wrist, or fit onto a curved chair.
That is exactly what a team of researchers at Penn State has achieved—using a surprisingly familiar material: the same shrinkable plastic used in children’s craft projects like Shrinky Dinks.
The researchers have developed a new way to create wireless, internet-connected electronics that can shrink and conform to complex 3D surfaces, including the human body and everyday household objects.
This breakthrough could lead to more comfortable wearable devices, better health monitoring systems, and smarter furniture and home accessories.
Led by engineering professor Huanyu “Larry” Cheng, the team was looking for a simple, low-cost, and widely accessible material to use as the base for shape-changing electronics.
Their goal was not just to create technology that works in high-tech labs, but something that could eventually be made cheaply and at large scale.
When they discovered the potential of shrinkable craft plastic, they realized it could offer the perfect solution.
These thin plastic sheets are inexpensive, easy to buy, and shrink evenly when heated.
But shrinking plastic alone is not enough to make smart electronics. The next challenge was figuring out how to print a working electronic circuit onto the plastic that would survive the shrinking process.
Traditional circuit materials like gold and silver are not only costly, but too stiff. When the plastic shrinks, these metals crack and lose their function.
Instead, the team turned to liquid metal, a special alloy of gallium and indium that stays liquid around room temperature.
This metal is flexible and highly conductive, making it a promising candidate for stretchable and shrinkable electronics. However, liquid metal has its own problems. It can be hard to control, and it does not naturally stick well to plastic surfaces.
To solve this, the researchers modified the liquid metal using a process called ultrasonication, which uses high-frequency sound waves to break the metal into tiny droplets. They mixed it with a chemical similar to detergent, changing the metal’s surface properties so it could more easily cling to the plastic.
At the same time, they treated the plastic with plasma, a process that helps the surface form stronger bonds with the metal. Together, these steps significantly increased the metal’s ability to stay attached while the plastic was shrinking.
When heat was applied, the plastic shrank down and the liquid metal droplets tightened into a more compact, dome-like structure. Surprisingly, this made the circuit even stronger and more conductive.
The metal also filled small holes in the plastic surface before hardening, creating a tightly interlocked structure. Adhesion was improved by around 20%, and the circuit remained fully functional.
Using this technique, the team was able to design tiny antennas that could be shrunk into precise 3D shapes.
These antennas can be attached to irregular objects without losing signal quality. This means everyday items, from chairs to cups to door handles, could potentially be converted into smart, connected devices without expensive redesigns.
As a first demonstration, the researchers created a wearable ring embedded with a tiny motion sensor. The ring could detect hand and finger movements and send that data wirelessly over a network. In the future, a device like this could help translate sign language into digital commands, track rehabilitation exercises, or monitor subtle changes in a patient’s movement.
The researchers believe this “shrink-to-fit” approach could be especially useful in healthcare. Custom-fitted, low-cost devices could be made for patients of all shapes and sizes to monitor heart rate, breathing patterns, posture, or rehabilitation progress.
Because the materials are affordable and the process is scalable, the technology has the potential to reach far beyond hospitals and into everyday life.
By turning a simple craft material into the foundation for advanced, internet-connected electronics, this research opens the door to a future where smart devices are not just powerful, but also flexible, personal, and accessible to everyone.
Source: Penn State.
