A fabric that may shrink to suit round inner organs with out crushing them might be used to watch electrical exercise within the physique. It contracts to lower than half of its preliminary size when moist, and may conform across the organs’ irregular shapes.

Junqi Yi at Nanyang Technological College in Singapore and her colleagues made this materials, known as WRAP, from a petroleum-derived polymer much like plastic. They tuned its molecular construction to imitate that of spider silk, which shortens when moist. The shrinkage occurs in each these supplies as a result of water disrupts bonds between chains of stretched molecules that then recoil.

Throughout a number of experiments, when the researchers added water to WRAP, it change into softer and stretchier, contracting as much as 65 per cent in size. For instance, a dry loop of the fabric with a diameter of 17 centimetres shrank to eight millimetres in diameter.

Yi says that WRAP achieves as a lot of a discount in dimension as plastic packaging movies that shrink when heated. However to be used contained in the physique, including water is a extra handy method to trigger shrinking.

She and her colleagues constructed mushy electrodes right into a loop of WRAP, then positioned it across the coronary heart of a rat. The moisture within the animal’s chest cavity made WRAP shrink and conform across the organ. They then used it to document {the electrical} alerts throughout the coronary heart, much like the these recorded by a standard epicardial electrogram. For a monitoring technique that requires implanting a tool within the physique, the method was minimally invasive, however the electrode had to get replaced after about two weeks as a result of it began to degrade, says Yi.

The truth that WRAP shrinks a lot and inside a couple of seconds is a notable development over present supplies, says Ximin He on the College of California, Los Angeles. She says that not having to pre-shape units produced from WRAP can be a bonus as a result of it might result in extra personalised units.

Christopher Bettinger at Carnegie Mellon College in Pennsylvania says that shrinking is mostly a useful gizmo in biomedicine, and a cloth that does so on demand may be used to clamp blood vessels or might be added to different supplies to make them aware of water of their setting.