Wearable devices have become a big part of modern health care, helping track a patient’s heart rate, stress levels and brain activity. These devices rely on electrodes, sensors that touch the skin to pick up electrical signals from the body.
Creating these electrodes isn’t as easy as it might seem. Human skin is complex. Its properties, such as how well it conducts electricity, can change depending on how hydrated it is, how old you are or even the weather. These changes can make it hard to test how well a wearable device works.
Additionally, testing electrodes often involves human volunteers, which can be tricky and unpredictable. Everyone’s skin is different, meaning results aren’t always consistent. Testing also takes time and money. Plus, there are ethical concerns about asking people to participate in these experiments, including making sure they are informed about the risks and benefits and can voluntarily participate.
Scientists have tried to create artificial skin models to avoid some of these problems, but existing ones haven’t been able to fully mimic the way skin behaves when interacting with wearable sensors. To address these limitations, my colleagues and I have developed a tool called a biomimetic skin phantom – a model that mimics the electrical behavior of human skin, making testing wearable sensors easier, cheaper and more reliable.
What is a skin phantom?
Our biomimetic skin phantom is made of two layers that capture the nuances of both the skin’s surface and deeper tissues. “Biomimetic” means it imitates something from nature – in this case, human skin. “Phantom” refers to a physical model or device made to mimic the properties of something real, like human tissues, so it can be used for research instead of relying on actual people.
Your skin is made up of multiple layers of cells.
OpenStax, CC BY-SA
The bottom layer mimics the deeper tissues under the skin. It is made from a gel-like substance called polyvinyl alcohol cryogel, which can be adjusted to have similar softness and electrical conductivity to real biological tissues. We chose this material because these qualities, along with its durability and wide use in biomedical research, make it a good stand-in for the deeper layers of skin.
The top layer mimics the outermost part of the skin, known as the stratum corneum. It is made from a silicone-like material called PDMS, which is mixed with special additives to match the skin’s electrical properties. Also widely used in biomedical research, PDMS is flexible and easy to shape to closely replicate the skin’s outer layer.
One unique feature of our skin phantom is its ability to mimic different levels of skin hydration. Hydration affects how well skin conducts electricity. Dry skin has higher resistance, meaning it opposes the flow of electricity. This makes it harder for wearable devices to pick up signals. Hydrated skin conducts electricity…
