Chemical engineers at Stanford University, Stanford, CA, have discovered that they could combine layers of flexible electronics and pressure sensors to create a wearable heart monitor thinner than a dollar bill and no wider than a postage stamp. The flexible skin-like monitor, worn under an adhesive bandage on the wrist, is sensitive enough to help doctors detect stiff arteries and cardiovascular problems.

To make the heart monitor both sensitive and small, the research team used a thin layer of rubber covered with tiny pyramid bumps. Each mold-made pyramid is only a few microns across, smaller than a human red blood cell. When pressure is put on the device, the pyramids deform slightly, changing the size of the gap between the two halves of the device. This change in separation causes a measurable change in the electromagnetic field and the current flow in the device.

The more pressure placed on the monitor, the more the pyramids deform and the larger the change in the electromagnetic field. Using many of these sensors on a prosthetic limb could act like an electronic skin, creating an artificial sense of touch. When the sensor is placed on someone's wrist using an adhesive bandage, the sensor can measure that person's pulse wave as it reverberates through the body.

They say that the devices could one day be used to continuously track heart health and provide doctors with a safer method of measuring a key vital sign for newborn and other high-risk surgery patients.