Sensors and other electronics are usually made of rigid and stiff material such as metals and plastics. They cannot be stretched, twisted or thrown, and should be handled with care. But that is about to change. Researchers from the Institute of Textiles and Clothing at PolyU have developed a new technology that allows electronics to drape comfortably around the human body. The researchers have engineered a new fabric that can conduct electricity, paving the way for stretchable electronics. The pressure sensitive fabric is made of flexible polymers and nano-carbon materials. Through advanced fabrication process, conductive nano-carbon materials were laced onto polymer to create a thin layer that can transfer electricity. When stretched or pressed, the thickness of this layer changes, which leads to a change in the electric current and the resistance. The fabric will react to a pull or compression with an increase in resistance so that strain and pressure can be measured.

To transform this novel idea into reality, Prof. Xiaoming Tao and her team have to overcome a challenge: a loss of conductivity under a high degree of deformation. Employing novel textile engineering techniques, they have developed a highly conductive polymer that can withstand significant stretching. This material is also highly sensitive and reliable for touch sensing. Principal investigator Prof. Tao explained, "Our new fabric can be stretched like a rubber band and has high sensitivity to strain. We've also made another one that can withstand and respond to very high pressure up to 2000kPa. They are water-proof, washable and excellent in resistance to fatigue." In the future, pressure sensors can be bent and stretched. More importantly, the flexible material is soft, light and breathable, and therefore is well tolerated by human skins. As it will work better and longer on human body, it opens up new possibilities for health care and medical applications such as wearable health monitoring devices. For example, a stretchy fabric sensor can measure intensive body movements and then send information wirelessly to a computer. Such electronics can adapt to any bent and moving body parts for health monitoring or remote control. This novel technology has been applied and presented as a pair of smart shoes for round-the-clock health watch without a single wire or electrode on a person. Fellow researcher Dr Aaron Wang illustrated, "The pressure-sensitive fabric is made into a touch sensor in the shape of a sole. When fitted into the shoes, the sensor can detect when an elderly person falls over and then send alerts or track down a missing person with dementia when he is out and about." The research team is anticipating a future where medical devices can integrate seamlessly into the human body to track a patient's vital signs and transmit the signals to his/her doctor. Dr Wang suggested more innovative possibilities in entertainment business, "Our stretchable sensors will be useful in fabric push buttons, game controllers and dance pads. Computer games will be more fun and edgy than ever." "Our ultimate goal is to develop a deformable system integrated with computer power, wireless technologies and environmental power sources, which I believe will have a profound impact on telemedicine, health care delivery and sports training," said Prof. Tao. This breakthrough was licensed to a start-up called AdvanPro Limited for further development and production.

In another development, MC10, a startup in Cambridge, Massachusetts, is getting ready to commercialize high performance electronics that can stretch. The technology could lead to such products as skin patches that monitor whether the wearer is sufficiently hydrated, or inflatable balloon catheters equipped with sensors that measure electrical misfiring caused by cardiac arrhythmias. icroelectronics have long "depended on a rigid, brittle wafer," says David Icke, the CEO. MC10 uses a few tricks to change that. To make both the hydration-sensing patch and the catheter, gold electrodes and wires just a few hundred nanometers thick are deposited on silicon wafers by conventional means, then peeled off and applied to stretchable polymers. The serpentine wires elongate when the polymers stretch, either when the balloon inflates in the heart or as the patch moves around on the skin. The electrodes measure electrical impedance to detect the electrical signals in cardiac tissue or moisture levels in the skin. The company is building on lab prototypes made by University of Illinois materials scientist John Rogers, a company co founder. Rogers's technologies have advantages over other approaches to flexible electronics. For example, organic polymer electronics can only bend, not stretch, and they are slower than devices made of inorganic semiconductor materials or precious metals such as gold, so they can't provide precise real-time biological readings. MC10's first product, expected to launch in late fall, will be a wearable device developed in a partnership with Reebok. The company has not disclosed any details. But in addition to the hydration patch, it is working on patches that use sensors to detect heartbeat, respiration, motion, temperature, blood oxygenation and combinations of these indicators. MC10's skin patches can wirelessly transmit information to a nearby smartphone. A phone with a near-field communication chip can be waved over the patch, or the patch can be paired with a thin-film battery made by a commercial supplier, allowing continuous data transmission. Next up will be balloon catheters that a cardiologist could snake through the heart to detect areas of misfiring cardiac tissue. Some of the prototypes in preclinical testing have dense arrays of electrodes that allow high-resolution mapping and ablation of that tissue. Further off are other medical devices, including implantable materials that conform to brain tissue, sensing seizures and stopping them.