Wearable device makes memories and powers up with the flex of a finger
Researchers from the University of Melbourne and RMIT University have invented an experimental wearable device that generates power from a user’s bending finger and can create and store memories, in a promising step towards health monitoring and other technologies.
Multifunctional devices normally require several materials in layers, which involves the time-consuming challenge of stacking nanomaterials with high precision. This innovation features a single nanomaterial incorporated into a stretchable casing fitted to a person’s finger. The nanomaterial enables the device to produce power simply through the user bending their finger. The super-thin material also allows the device to perform memory tasks.
The team, led by RMIT University and the University of Melbourne, in collaboration with other Australian and international institutions, made the proof-of-concept device with the rust of a low-temperature liquid metal called bismuth, which is safe and well suited for wearable applications.
Dr Ali Zavabeti with bismuth metal and PhD scholar Xiangyang Guo holding the wearable device in a petri dish in their lab (left to right) at RMIT University. Credit: Seamus Daniel, RMIT University.
Senior lead researcher Dr Ali Zavabeti, Lecturer in the Department of Chemical Engineering (UoM) and Adjunct Principal Research Fellow at RMIT University, said the invention could be developed to create medical wearables that monitor vital signs – incorporating the researchers’ recent work with a similar material that enabled gas sensing – and memorise personalised data.
“The innovation was used in our experiments to write, erase and re-write images in nanoscale, so it could feasibly be developed to one day encode bank notes, original art or authentication services,” said Dr Zavabeti.
During experiments, the team found that the device exhibited exceptional responsiveness to human movements, making it a promising candidate for wearable technologies.
“We tested natural motion behaviour with the device attached to a finger joint, with an average output peak of about one volt,” said Dr Zavabeti.
The device was able to perform the memory functions of “read”, “write” and “erase”, which included using the RMIT logo and a square-shaped insignia as demonstrations of these capabilities. The device, which was not worn by a user during these memory experiments, wrote and stored the logo and symbol in a space that could fit 20 times within the width of a human hair.
Lead author and PhD student Xiangyang Guo from RMIT said the team can print layers of bismuth rust, otherwise known as oxide, in just a few seconds.
The team’s innovation features a single nanomaterial incorporated into a stretchable casing fitted to a person’s finger. Credit: Seamus Daniel, RMIT University.
“We fundamentally investigated this instant-printing technique for the first time using low-melting point liquid metals,” said Guo, who works under the supervision of Dr Ali Zavabeti and Professor Yongxiang Li.
The team demonstrated that engineering materials at the nanoscale can present enormous opportunities in a range of functions, from sensing and energy harvesting to memory applications.
“Bismuth oxide can be engineered to provide memory functionality, which is critical for many applications,” Guo said.
“The material can act as a semiconductor, meaning it can be used for computation. It is a nanogenerator, meaning it is energy efficient with a green energy supply from environmental vibrations and mechanical movements.”
Guo also said bismuth oxide was likely to cause less irritation to skin, compared with silicon, and it was durable, so it was stretchable and could be integrated into wearable technologies.
Bismuth metal. Credit: Seamus Daniel, RMIT University.
The team is keen to collaborate with industry partners to further develop and prototype this invention as they plan to adapt their approach for other low-temperature liquid and solid metals and alloys that could be developed for personalised wearables.
The Australian Research Council funded the research, which was also supported by the National Computational Infrastructure, as well as the Microscopy and Microanalysis Facility (RMMF) and Micro Nano Research Facility (MNRF) at RMIT and the Department of Chemical Engineering and Physics at the University of Melbourne.
The team included researchers from the University of Toronto, Western Sydney University, University of Sydney, University of New South Wales and Australian National University.
The researchers’ peer-reviewed article, “Multi-Functional Atomically Thin Oxides from Bismuth Liquid Metal”, is published in Advanced Functional Materials (DOI: 10.1002/adfm.202307348).