High-tech thread can produce electricity

Nanotechnology researchers at the University of Texas (UT) at Dallas have created a new thread from carbon nanotubes that can efficiently convert mechanical motion into electricity.

A team member wears twistron stitching gloves. Photo: UT

In a study published January 26 in the journal Nature Energy , the UT Dallas team and colleagues describe improvements to a high-tech thread they invented called a "twistron," which produces electricity when it is damaged. stretch or twist. The new improved version has the same texture as traditional wool or cotton yarn. The twistron thread sewn into the fabric can sense and collect human movement. When placed in seawater, the twistron can collect energy from the motion of ocean waves, even charging supercapacitors.

First described by the team in a paper published in the journal Science in 2017, twistron is composed of carbon nanotubes (CNTs). Those are carbon pillars 10,000 times smaller in diameter than a human hair. To create the twistron, the nanotube is twisted into an ultra-lightweight, high-strength fiber that can integrate electrolytes. Previous versions of twistron were highly resilient. Electricity is generated from the thread through repeated pulling and dropping or twisting and stretching.

In the new study, Dr. Ray Baughman, director of the Alan G. MacDiarmid Institute of Nanotechnology at UT Dallas, and colleagues did not twist the thread to the point of winding. Instead, they wound three twisted strands of carbon nanotubes to create a thread. In experiments with the new thread, the team demonstrated an energy conversion efficiency of 17.4% for the stretch energy harvesting and 22.4% for the torsion energy harvesting. The previous version only achieved a maximum energy conversion efficiency of 7.6% for both types of energy harvesting.

Baughman says the improved performance of twistrons results from the lateral compression of the thread when stretched or twisted. The process of bringing grafted fibers into contact with each other in a way that affects the electrical properties of the fiber. The researchers found that the triple fiber fusion provides optimal performance. They conducted a number of experiments with grafted twistron fibers. In one experiment, they simulated electricity generation from ocean waves by attaching a twistron filament between a balloon and the bottom of a tank filled with salt water. The team also arranged multiple twistron filaments in clusters weighing just 3.2 g and repeated the stretching operation to charge the supercapacitor. The result is a supercapacitor with enough power to power 5 small diode bulbs, a digital clock and a temperature/humidity sensor.

In addition, the researchers sewed twistron yarn into a piece of cotton fabric, then wrapped it around a person's elbow. The electrical signal generated when the person bends the elbow repeatedly demonstrates the potential of using this fiber to sense and harvest human movement.