Lightweight sensor measures heart rate and body movement

In use, the patch employs tissue-contact impedance, a real-time electrocardiogram (ECG), and an accelerometer to monitor physical activity.

The electronics module measures less than two by two centimetres, thanks to advanced system in package (SiP) technology from Japan’s Shinko Electric Industries. It is further claimed that high accuracy algorithms, low power consumption, and small size and weight make the patch suited to consumer applications.

A number of activity monitors exist that can count the number of steps a person takes, or calories they’ve burned. Heart rate is a key input in determining activity levels, so monitors that can be worn comfortably on the chest offer the greatest accuracy. This, in turn, increases the demand for small, lightweight monitors that can flex and move with a person’s body.

Imec and Holst Centre claim their patch makes such applications possible because it combines ultra-low power electronics and flexible electrode technology to provide the end user with a 1-lead ECG, a tissue-contact impedance sensor and a 3D accelerometer.

Data is processed and analysed locally, and relevant information is transmitted via Bluetooth Smart (BLS). According to Imec, the patch acquires, processes and communicates data with minimal energy, allowing extended use with smaller batteries. Moreover, the Bluetooth Smart link provides a standardised communication channel to mobile devices, including smart phones and tablets.

Researchers from Imec used Shinko’s SiP technology to integrate this functionality into a module measuring 17.4mm x 17.4mm, which represents a PCB area reduction of 52 per cent compared to previous generations of the module.

The module was then integrated into a flexible and stretchable patch designed by Eindhoven-based Holst Centre. The design is said to combine system in foil technology with stretchable, integrated electrodes to create a lightweight patch that can be worn comfortably on the chest for extended periods. The module’s small size and the flexibility of the patch reduce motion artefacts, thereby providing accurate and reliable monitoring.

The patch was developed in the framework of Imec’s and Holst Centre’s Human++ program, which aims to address the need for better, more efficient healthcare monitoring systems. Imec and Holst Centre say they are now looking for partners interested in industrialising the concept.