Biodegradable and disappearing bandages and sensors advance sustainable monitoring and healing:
Researchers at Northwestern University, Evanston, Ill., and the University of Sussex, Brighton, England, have created prototypes of new environmentally sustainable devices that can monitor blood pressure and heartbeat, or heal persistent afflictions such as diabetic ulcers.
The devices are also far more advanced than proof-of-concept stage; the Northwestern device, a transient bandage that uses electrotherapy to both monitor and heal diabetic wounds, is resorbed into the body. It may be ready for human trials within a year to 18 months, according to Guillermo Ameer, director of Northwestern's Center for Advanced Regenerative Engineering. The bandage consists of two small molybdenum electrodes connected to a battery-free power-harvesting unit and a near-field communications module that communicates with control software in a smartphone or tablet.
In a study conducted on diabetic mice published in Science Advances, Ameer and his collaborators, including resorbable electronics pioneer John Rogers, found the device led to 30 percent faster healing than a control group using ordinary bandages.
The device works by transmitting a small current from the outer ringlike electrode, which sits around the wound site, to the inner flower-shaped electrode, which is about 120 micrometers across and sits atop the wound. (The mouse study used about 1 volt of current [sic], and Ameer said that may change in upcoming studies on larger animals.) The current stimulates healthy skin regeneration, the progress of which is measured by current differential between the electrodes. As the wound heals and dries, the current differential [sic] decreases.
Perhaps the most compelling element of the device is the inner electrode. As the wound heals, the regenerated skin grows over the electrode and completely absorbs it. The outer ring electrode and the accompanying power and communications unit are detachable from the inner electrode. Results of the mouse study showed molybdenum concentrations in the body returned to those similar to the control group's within 22 weeks.
While a portion of the Northwestern device bioresorbs itself into the body, the sensor developed at the University of Sussex is completely biodegradable. It is composed of food-grade algae powder added to a graphene suspension composed of graphite, sodium cholate, and deionized water, then dried to form a nanocomposite sheet. When soaked in a yet another food-grade component —a calcium chloride water bath—the sheet swells and creates a conductive hydrogel.
The device, described in ACS Sustainable Chemistry & Engineering, is also extremely flexible for a nanocomposite (with a Young's modulus just 0.6 pascal), and sensitive enough to measure an object of just 2 milligrams of mass, which the inventors likened to the pressure created by a single raindrop, on its surface. [...]
The study's corresponding author, Sussex material-physics lecturer Conor Boland, differentiated his lab's work, which uses electromechanical sensing, from the Northwestern bandage, which uses electrochemical sensing, but said both approaches can have legitimate uses in human health care. For example, he said, his team is already working on turning the algae mixture into a material that mimics human skin's mechanical properties, but also has the electronic capabilities to monitor blood pressure and breathing rate.
Journal Reference:
Joseph W. Song, Hanjun Ryu, Wubin Bai, et al., Bioresorbable, wireless, and battery-free system for electrotherapy and impedance sensing at wound sites [open], Sci. Adv., 2023. DOI: https://www.science.org/doi/10.1126/sciadv.ade4687
Adel A. K. Aljarid, Kevin L. Doty, Cencen Wei, et al., Food-Inspired, High-Sensitivity Piezoresistive Graphene Hydrogels [open], ACS Sustainable Chem. Eng. 2023, 11, 5, 1820–1827. DOI: https://doi.org/10.1021/acssuschemeng.2c06101
