Materials, Methods, and Optimized Designs for Soft Wearable Electronics with Significantly Reduced Motion Artifacts

Wearable electronics are changing healthcare and increasing possibilities for human-machine interfaces. Soft electronics, directly mounted on the skin, can monitor long-term heart rate trends or direct smart prosthetics' motion. However, these capabilities are only as good as the signal quality obtained. These wearable devices are worn in the real world, often suffering from motion artifacts not previously found when measured in a stationary setting such as a clinic or laboratory. Motion artifacts can mimic many biosignals by having a similar amplitude and frequency range, making them hard to filter out. A significant source of motion artifacts is from relative motion between the sensor and the signal source. Given human tissue's elastic nature, most body-mounted sensors undergo more relative motion than on a comparable rigid machine. Here, this work introduces a comprehensive study of materials, methods, and optimized designs that can significantly reduce motion artifacts via strain isolation, increased adhesion, and enhanced breathability for long-term recordings. Skin strain is another source of motion artifacts that can disturb electrodes' contact impedance and temporarily change the biopotential within the skin. We present a prototype electrocardiogram (ECG) device that uses a strain isolating layer to reduce skin strain at the electrode. This strategic integration of soft and hard materials reduces motion artifacts by stabilizing the electrode, while allowing freedom of movement elsewhere to maintain gentle contact with the skin. These solutions are demonstrated for long-term ECG collection but have application for any skin-mounted wearable device.