Temporary tattoos provide signals to medical devices
If you are in hospital for monitoring, sensors measure electrical signals in your body. If they slip, they become inaccurate. Temporary tattoos are designed to remedy this.
Engineers at Pennsylvania State University are researching a special alternative for medical sensors: paintable tattoos with electrodes. They are connected to medical measuring devices for EKGs, EEGs, and EMGs, which record brain, heart, and muscle activities. This way, they can help detect heart attacks, measure brain waves, and control robotic prostheses.
The tattoos solve a problem with prefabricated metal or hydrogel electrodes: these can slip. For example, due to movement over longer periods, or if the skin sweats or is hairy.
Engineers at Penn State University have developed a solution based on paintable tattoos. These consist of conductive ink, through which the sensors for wearable devices (EEGs, EKGs, EMGs) are powered.
The team has filed a provisional patent for this ink. It consists of an aqueous solution mixed with polymers and acidic additives. It is transparent and sticky but can be colored with food coloring. On the skin, it dries in under ten minutes.
For example, a doctor can use the ink to paint a cute fox or a shark on the skin. Due to this playful character, the electrodes are particularly suitable for children. A medical device is much more fun if it is applied using a temporary tattoo of a favorite animal. That's why the engineers plan to distribute the ink to pediatric practices in the future.
Reliable for twelve hours
A porous silver mesh with connecting electrodes connects the ink to the sensors. It is placed on the painted tattoo before it dries – so it adheres directly to the skin.
Afterward, the engineers connect the mesh to a port on the monitoring device. They then attach this device to the skin under clothing with adhesive tape. The electrical signals are finally transmitted via Bluetooth to a computer.
An air gap can form between current sensors and the skin, leading to inaccurate measurements. The ink lies directly on the skin, and the electrodes of the silver mesh can expand to over 150 percent of their original size. This allows sweat to pass through the mesh without affecting adhesion, accuracy, or comfort.
The electrodes painted with the ink can record EKG signals for up to 12 hours and hold up during physical activity. The electrodes also record muscle signals so well that a robotic hand can be remotely controlled. After 12 hours, the electrodes must be washed off and repainted.
The next step is a safety check for MRI compatibility. The initial tests were positive, but it must be ensured that the conductive components of the painted ink do not heat up in the strong magnetic field. This would lead to burns on the skin. The engineers also want to further research how the ink behaves with heavy sweating and different skin types, and how to extend the wearing time.
For commercial use, the product must undergo clinical trials and be certified by the relevant authorities. A first step is already underway with the patent application. However, it will still take several years before you can actually get such a tattoo.
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