The invention of the printing press revolutionized duplication of the written word, giving the hands of tired scribes a break and making written material more accessible. A similar breakthrough has happened in reverse in the McKelvey School of Engineering at Washington University in St. Louis.
Researchers working with Chuan Wang, associate professor of electrical & systems engineering, have developed ink pens that allow individuals to handwrite flexible, stretchable optoelectronic devices on everyday materials including paper, textiles, rubber, plastics and 3D objects. Flexible optoelectronics for emitting and detecting light, which are already found in everyday objects like smartphones and fitness trackers, can bend, fold and flex while maintaining functionality.
In a paper published in Nature Photonics, the team reports their simple and versatile fabrication approach to allow anyone to make a custom light-emitting diode (LED) or photodetector without the need for any specialized training or bulky equipment.
The team’s environmentally friendly, innovative handwriting approach empowers individuals to create multicolor LEDs and photodetectors in mere minutes. The technology harnesses the simplicity of a ballpoint pen, filled with specially designed inks made of conductive polymers, metal nanowires and crystalline materials called perovskites to generate a wide spectrum of emission colors. By writing layer upon layer with these functional inks, much like using multicolored pens, a variety of functional devices including disposable electronics, such as smart packaging, and personalized wearables, such as biomedical sensors, can be created cheaply, easily and quickly.
Though the team had already developed printable ink, translating it for standard ballpoint pens that are feasible for handwriting on everyday materials required a few tweaks to control wettability and improve writability.
The creation of ink pens that work on all substrates from paper to party balloons overcomes critical limitations of traditional LED fabrication – particularly the requirement of flat, smooth substrates and cost-prohibitive clean-room fabrication equipment – and opens the door for next-generation wearable electronics to permeate daily life in an unprecedented way.
Wang envisions future applications for handwritten electronics limited only by the user’s imagination. Immediate uses range from educational purposes and science popularization to electronic packaging and clothing to medical sensors and bandages.
The accessibility and flexibility of this method could democratize electronic manufacturing, allowing the possibility of customized, stretchable electronic devices to become part of the fabric of everyday life.
News Source: Washington University in St. Louis
