A team of scientists from Empa, the Swiss Federal Laboratories for Materials Science and Technology, developed a chest strap device for the long-term monitoring of patients with heart and circulatory problems. The new system records an electrocardiogram (ECG) of the wearer.
Gel electrodes have been necessary for reliable long-term ECG measurements, but the components dry out within 24 hours, after which they no longer produce usable signals. The EMPA device self-moistens and continuously allows minimal quantities of water to permeate through it.
The flexible wetting elements are filled with 30 mL of water. The "reservoir" is a hollow space between a watertight membrane and a textile layer which is permeable to water vapor. The reservoir continually supplies minute quantities of water vapor to keep electrodes moist, lasting for at least five days before needing a refill.
The electrodes are capable not only of acquiring the wearer’s heart signals, but also all the other bodily signals necessary for cardiological analysis. The interleaved fiber is made of polyethylene terephthalate (PET) and is given a special plasma coating by scientists from Empa’s Advanced Fibers laboratory.
The 100-nm fiber coating consists of two layers. An inner layer of silver conducts the electrical signals and prevents the growth of microorganisms, while the outer layer of titanium ensures signal stability and prevents skin irritation and the release of silver particles.
Each chest strap contains two sensor pads, which are connected directly to a data logger. The recorded signals are transmitted on to a central data collection unit or a standard monitoring device. The data logger is attached with snap fasteners so it can be removed in order for the belt to be washed.
