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Stretchy LEDs may have clothing, packaging, biomedical uses

Swatches | November 1, 2023 | By:

Junyi Zhao demonstrates using a ballpoint pen to write custom LEDs on paper (left). The same pens can be used to draw multicolored designs on aluminum foil (top right) and to create light-up sketches (bottom right). Images: Wang Lab

Building on previous research that created stretchable inkjet LEDs, researchers at Washington University in St. Louis, Mo., have reformulated the ink to come out of a pen for writing by hand as well, much like layering writing with multicolored pens. 

Stretchable optoelectronic devices have potential uses in quickly and easily creating light-up clothing, smart packaging and cheap biomedical sensors in personalized wearables or bandages. Associate professor Chuan Wang, Ph.D., says the sensors and bandages “could have photodetectors and infrared LEDs drawn onto them for measuring pulse oximetry or to speed wound healing.”

The inks are made of conductive polymers, metal nanowires and crystalline perovskites that go on in separate layers. The latter can have different compositions to create a wide spectrum of colors. Each single layer is independently stretchy. To work on porous substrates such as textiles, the ink had to not run or mix but be more wet than the inkjet version in order to come out of the pen. 

The work was published in Nature Photonics in August 2023 and was supported by the Bill & Melinda Gates Foundation.

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