For over 12 hours, electrodes painted onto skin recorded a test subject's heart rhythm while they exercised, sweated, and moved their arm without falling off. A team at Pennsylvania State University, working with researchers from MIT and the Suzhou Institute of Biomedical Engineering and Technology, developed a conductive polymer ink that can be applied to skin with a regular paintbrush while simultaneously capturing ECG signals, muscle activity, and brain waves. Results appeared on July 13, 2026 in the Proceedings of the National Academy of Sciences.
How electrode tattoos differ from clinical patches
Conventional ECG electrodes stick to skin as gel-based disposable patches. The gel bridges contact resistance between electrode and skin surface. However, it dries out within hours, degrading signal quality. During physical activity, patches frequently detach. For long-term monitoring or for children who refuse patches, this is impractical.
Smartwatches like the Apple Watch offer single-channel ECG but are limited to the wrist and cannot measure brain waves or fine-grained muscle activity. Flexible electrode patches from earlier research generations, such as systems from Epidermal Electronics around Northwestern University researcher John Rogers, required laboratory transfer procedures and could not be applied individually with a brush.
The Penn State team's solution relies on a water-based polymer mixture with acidic additives. According to the PNAS publication, the ink dries unaided on skin in less than 10 minutes, much faster with a hair dryer. A stretchable silver fiber mesh then connects the painted electrode wirelessly or via cable to a recording device. This mesh stretches up to 150 percent of its original length without breaking, keeping the electrical connection stable even during arm and hand movements.
PEDOT:PSS as the conductive core
Conductivity is generated through PEDOT:PSS, short for poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate). The polymer is known in materials research from flexible organic solar cells and displays. It is considered biocompatible and has proven skin-compatible in previous medical material studies.
According to Penn State's press release, standard food dyes can be mixed into the ink without compromising conductivity. Professor Huanyu Cheng, who led the research group, explained: "The ink itself almost behaves like face paint. It starts out almost transparent, but you can use food dye." This opens the technology to an aspect often underestimated in clinical trials: acceptance in children. Children who refuse medical patches might tolerate a colorful design painted on any body location.
Lead author of the study is Wanqing Zhang, a PhD candidate in the Department of Engineering Science and Mechanics at Penn State University. The research group has filed a provisional patent for the ink.
ECG, brain waves and robotic arm control
Within the study, researchers tested three application classes. For ECG monitoring, participants applied the ink to their torso and then performed everyday activities and a sports session. The electrodes adhered for over 12 hours and, according to the university, delivered signal quality comparable to commercial gel electrodes.
For brain wave measurement, electrodes were applied to the scalp, previously cumbersome and expensive with rigid EEG helmets. Flexible paintable electrodes could significantly lower the threshold for ambulatory brain activity measurement, such as for long-term epilepsy monitoring.
Most striking is the demonstration of prosthesis control: researchers painted the ink on a test subject's forearm and had them perform various hand movements. The muscle action potentials generated were analyzed in real time by a computer system and translated into control commands for a robotic prosthesis. Existing EMG-based prosthesis systems use fixed electrodes at the stump, which can only measure at predefined points. Paintable electrodes could be placed in any pattern to capture more muscle groups, enabling finer control.
According to Penn State, one bottle of ink is sufficient for several electrodes over several days to a week. The ink washes off with water and can be reapplied afterward.
Long-term studies still needed before clinical use
Despite promising laboratory results, several steps are needed before the technology can be used in clinical diagnostics. First, long-term studies on skin compatibility with daily use over weeks are lacking. While PEDOT:PSS is considered biocompatible, systematic data for continuous skin contact in this format remain outstanding.
For diagnostic use in humans, the electrode must also be approved as a medical device, in the US by the FDA, in Europe through CE marking under the Medical Device Regulation (MDR). These approval procedures typically take three to seven years for new sensor classes.
For research laboratories, the technology is already usable today. Penn State University has not communicated when it will be available as a commercial product.