Technology: Get smart

Developments in industry and academia bring exciting new functionalities to conventional rubber materials

The capability of elastomeric materials to act as electronic sensors and to self-heal is driving innovate research and partnerships in the rubber industry.

Toyoda Gosei, for instance, this month exhibited its next-generation ‘e-rubber’ materials for dielectric actuators and sensors at a sports business expo in Japan.

Displays included soft e-rubber actuators that offer a next-generation power source in place of electromagnetic motors and soft, tactile/pressure sensors.

The company also showed ideas to attach lightweight sensors to sports shoes and other sporting goods.

The e-rubber parts were said to be resistant to impact, lightweight, and soft and could, for example, be attached to shoe insoles.

In another interesting display, Toyoda Gosei showed how vibrations in a balloon filled with water could be remotely transferred on to the surface of another balloon without water – a technology being jointly developed with Keio University.

Toyoda Gosei also recently showed off e-rubber at the RoboDEX robotics show in Tokyo: uses including a new power source instead of electromagnetic motors in artificial muscles as well as tactile and motion sensors for robots.

The company’s displays included a supermarket stocking robot that arranged soft food items on shelves, and one able to sort boiled eggs with and without shells by touch.

French rubber and plastics parts maker Hutchinson has, meanwhile, announced a partnership with the WIMS2 (Wireless Integrated MicroSensing and Systems) centre, affiliated with the University of Michigan.

WIMS2 is advancing industrial applications for sensor-activated microsystems through fundamental research, training and industry collaborations.

The link-up, said Hutchinson, will help it “to seek out future talents while pursuing projects that lie within the [company’s] “future mobility” innovation strategy.”

Also in the US, researchers at the University of Southern California (USC) Viterbi School of Engineering have developed a rubber material that can be 3D-printed into self-repairing products, USC reported 5 Feb.

The manufacturing process involves photopolymerisation reactions with thiol groups, which are also oxidised into disulfides groups that reform – or self-heal – when broken.

The research team was led by assistant professor Qiming Wang, working with Viterbi students Kunhao Yu, An Xin, and Haixu Du, and University of Connecticut assistant professor Ying Li.

Finding the right ratio between the two chemical groups was the key to unlocking the materials’ unique properties, according to the researchers.

“When we gradually increase the oxidant, the self-healing behaviour becomes stronger, but the photopolymerisation behaviour becomes weaker,” explained Wang.

“Eventually we found the ratio that can enable both high self-healing and relatively rapid photopolymerisation,” the team leader added.

In five seconds, the materials can be printed into a 17.5-millimetre square, according to the USC report.

Whole objects, it added, can be completed in around 20 minutes, with parts able to repair themselves in just a few hours.

In a study, published in NPG Asia Materials, the new material was shown to self-heal on a shoe pad, a soft robot, a composite material and an electronic sensor.

After being cut in half, the rubber healed completely in just two hours at 60°C – retaining strength and function.

“Under different temperatures – from 40°C to 60°C – the material can heal to almost 100%,” said Yu.

“By changing the temperature, we can manipulate the healing speed, even under room temperature the material can still self-heal,” the researcher said.