IMEC, a Belgium/Netherlands research center in nanoelectronics and nanotechnologies, has developed what it describes as a “wireless, flexible and stretchable” ECG patch for comfortable continuous cardiac monitoring:
The ECG patch is a hybrid system combining electronic assembly on a flexible Polyimide substrate and textile integration. This allows achieving flexibility and stretchability. Standard ECG electrodes are used for attachment to the body. The ECG patch can fit body curves and allows optimal, personalized, placement of the electrodes. It can therefore be used to monitor cardiac activity ‘on-the-move’ in daily-life conditions, thus opening new perspectives for cardiovascular disease management. Placed on the arm or on the leg, the same system can also be used to monitor muscle activity (EMG).
The core of the wireless ECG patch consists of a miniaturized wireless sensor node integrated on a flexible, Polyimide, substrate. It integrates IMEC’s proprietary single-channel ultra-low-power biopotential ASIC for the monitoring of the ECG signal. It also includes a commercial microprocessor enabling local digital signal processing, a 2.4GHz radio link and a miniaturized rechargeable Lithium-ion battery. The battery is placed under the electronic components to ensure the local rigidity required for long-term functioning of the electronic components. In addition, the sensor node features a fork-antenna and a snap-on connector (for connection to the electrode). The total size of the flexible core part is 60x20mm2. Two additional snap-on connectors are coupled to the central part with short conductive wires. The complete system is then integrated into textile to form the ECG patch. The use of very short wires and their integration into textile allows the minimization of an important source of artifacts due to wire movement.
The wireless ECG patch can work in continuous monitoring mode, in which the ECG – or EMG – data is continuously transmitted to the receiver (sample frequency between 250 and 1000Hz). For cases in which only heart rate information is required, the heart rate can be computed locally on the node and then sent over-air to the receiver. This allows drastic reduction of the use of the radio and hence increases the autonomy of the system. The embedded miniaturized rechargeable battery offers a capacity of 175mAh, which allows for an optimal autonomy of the system varying from one day in continuous monitoring to several days for simple heart rate monitoring. The signal is sent to a receiver connected to a PC or to a data-logger for later download on a computer.