Holst Centre and imec have developed a small prototype flexible health patch that comfortably and accurately monitors physical activity. The researchers used system-in-package technology from Shinko Electric Industries Co. Ltd. to integrate its sensors’ functionality into a module that measures 17.4 by 17.4 mm, representing a 52% reduction of printed-circuit board (PCB) area compared to previous generations. The module is then integrated into a flexible and stretchable patch designed by Holst Centre that weighs just 10 g, which is half the weight of similar products. 

The patch combines ultra-low-power electronics and flexible electrode technology. It includes a one-lead real-time electrocardiogram (ECG), a tissue-contact impedance sensor, and a 3D accelerometer. Data is processed and analyzed locally. Relevant information is transmitted via Bluetooth Smart (BLS) to mobile devices such as smart phones and tablets. Thanks to its flexibility and small size and weight, users can wear it comfortably during exercise and other activity. Since it is so small, it reduces motion artifacts for more accurate and reliable monitoring.

“Comfortable, lightweight wearable systems for personal health monitoring are emerging, given their promise to better analyze patients’ physiological parameters,” said Chris Van Hoof, program director of wearable healthcare at Holst Centre/imec. “We are excited about working with Shinko to successfully bring the technology closer to consumers’ needs.”

The processor is a custom imec ultra-low-power DSP. It is part of an imec ultra-low-power system-on-chip (SoC) that performs the cardiac signal conditioning (amplification, filtering) and data analysis. Also, it is power-optimized for typical cardiac rhythm analysis algorithm computations (LMS, PCA, CWT) and consumes less than 50 µW in operation. The entire analog front end, including the analog-to-digital converters, consumes less than 40 µW.

A flexible, commercial, 15-mAh battery from Solicore provides the power. The Texas Instruments CC2540 provides Bluetooth Low Energy radio functionality. For most of imec’s wearable devices, the organization creates graphical user interfaces on smartphones and tablets for interfacing and visualization. Also, imec has application programming interfaces for both iOS and Android as well as a basic interface for the patch, which generally are improved together with imec’s customers.

The patch was developed as part of imec’s and Holst Centre’s Human++ program, which addresses the need for better, more efficient healthcare monitoring systems. Holst Centre and imec are now looking for partners that are interested in industrializing the concept.