University of Pennsylvania researchers have developed an electrode and an electrode array, both made of layers of silicon and molybdenum that can measure physiological characteristics (like neuron signals) and dissolve at a known rate (determined by the material’s thickness).
The researchers showed the dissolvable electronics could be used in a complex, multiplexed ECoG (intracranial electroencephalography) array over a 30-day period.
As the researchers note online in Nature Materials, this new technology offers equal or greater resolution for measuring the brain’s electrical activity, compared to conventional electrodes, while eliminating “the risks, cost, and discomfort associated with surgery to extract current devices used for post-operative monitoring,” according to senior co-author Brian Litt, MD, a professor of Neurology, Neurosurgery, and Bioengineering at the Perelman School of Medicine.
Other potential uses of the dissolvable electronics include:
Disorders such as epilepsy, Parkinson’s disease, depression, chronic pain, and conditions of the peripheral nervous system. “These measurements are critically important for mapping and monitoring brain function during and in preparation for neurosurgery, for assisting in device placement, such as for Parkinson’s disease, and for guiding surgical procedures on complex, interconnected nerve structures,” Litt said.
Post-operative monitoring and recording of physiological characteristic after minimally invasive placement of vascular, cardiac, orthopaedic, neural or other devices. At present, post-operative monitoring is based on clinical examination or interventional radiology, which is invasive, expensive, and impractical for continuous monitoring over days to months.
Heart and brain surgery for applications such as aneurysm coiling, stent placement, embolization, and endoscopic operations. These new devices could also monitor structures that are exposed during surgery, but are too delicate to disturb later by removing devices.
More complex devices that also include flow, pressure, and other measurement capabilities. The research was funded by the Defense Advanced Research Projects Agency, the Penn Medicine Neuroscience Center, a T32- Brain Injury Research Training Grant, the Mirowski Family Foundation, and by Neil and Barbara Smit.
In related research, Chinese researchers have developed a memristor (memory resistor) with biodissolvable components, using a 30 nm film of egg albumin protein on a silicon film substrate and electrodes made out of magnesium and tungsten.*
Testing showed that the device’s bipolar switching performance was comparable to oxide-based memristors, with a high-to-low resistance ratio in the range of 100 to 10,000. The device can store information for more than 10,000 seconds without any deterioration, showing its high stability and reliability.
Under dry conditions in the lab, the components worked reliably for more than three months. In water, the electrodes and albumin dissolved in two to 10 hours in the lab. The rest of the chip took about three days to break down, leaving minimal residues behind, the researchers report in the journal ACS Applied Materials & Interfaces.
The research was funded by the National Natural Science Foundation of China and the Research Fund for the Doctoral Program of Higher Education of China.