In order to conduct electrical signals from the skin, the electrodes on heart rate monitors need to be slightly moist. That's why gel is first applied to patients' skin. Unfortunately, that gel dries up within 24 hours. Now, however, scientists from Switzerland's Empa research institute are developing a solution – a self-moistening heart rate-monitoring chest strap, for use in situations where electrocardiograms (ECGs) need to be recorded over a period of several days.
The device features a 30-mL (1-oz) reservoir, that wicks a steady supply of water to a flexible wetting element that sits between the patient's skin and the built-in electrodes. That element is made of polyethylene terephthalate, a textile that is able to contain liquid water, but that also allows water vapor to permeate through to the skin.
That textile is aided by an extremely thin two-layered coating. An inner layer of silver helps conduct signals and prevent the growth of bacteria, while an outer layer of titanium keeps the signal stable, prevents skin irritation, and keeps silver nanoparticles from being released.
This setup is duplicated in two sensor pads, that are wired to a data logger which is attached to the strap with snap fasteners. Once activated, the system can continuously monitor the wearer's heart rate for at least five days before needing a refill. After that, the logger can be removed and the strap itself can be washed.
The technology is currently in prototype form, and has been tested on over 100 male and female volunteers. Clinical trials are planned to take place soon.