Electronics Weekly
Telemedicine brings a radical transformation, making healthcare effective and more accessible to everyone.
Advances in semiconductor technologies are playing a key role in the digital transformation of healthcare, enabling the design of a variety of wearables, smaller portable equipment and multifunctional medical devices addressing complex healthcare systems and also applicable to smart hospitals with advanced engineering.
In medical and healthcare domains, a wide portfolio of semiconductor technologies and products – from optical and bio sensors to analogue front end-processing and embedded AI capabilities – is a key ingredient to allow the maximum flexibility of system design.
A wearable case study
To develop a wearable electronic skin patch platform that can potentially address multiple use cases, the first critical step is to understand the specific needs of the market. Cardiology and radiology have historically been at the forefront in adopting medical innovations. Exploring what the market wants and expects from these wearables allowed development to focus on the unmet needs of today’s professionals and so improve on the numerous e-skin patches currently in the market.
In this project, features such as signal detection and quality, wearability, longer usage and user convenience, alongside device miniaturisation and integration, placement in the body, battery life, power management and embedded intelligent functions were the key focus in targeting large-scale adoption of wearable cardiac skin patches. The multiple requirements and aspects represented a genuine challenge due to the need to combine all these features at the same time, while not compromising wearability and ease of use of the final device.
Microelectronics in an e-skin patch
Key components in this example include ST’s biosensor that combines on-chip analogue sensing for electrocardiography (ECG) with a highly sensitive accelerometer for simultaneous seismocardiography (SCG) detection. Analogue to digital conversion, embedded digital processing, power management and AI complement this design, which can be adopted in all existing commercial smart patches in the healthcare wearable market.
Figure 1: Electronic skin patch with three electrodes for ECG (blue), over-sternum sensor for SCG (red) and GCG
Why SCG? Among the existing techniques for monitoring cardiac health, the electrocardiography is the gold standard to measure the electrical signal of the heart. SCG is a known method to measure the heart’s mechanical function by monitoring chest vibrations while the heart beats. SCG sensors capture the chest acceleration induced by the motion of the myocardium, using an accelerometer mounted on the lower part of the sternum. SCG has been used separately in clinical research, demonstrating its validity. The combination of ECG and SCG can provide more reliable cardiac health monitoring compared to using either technique on its own.
The dual-measurement of electrical and mechanical cardiac bio-signals, synchronised in a single, compact device, has the additional advantages of providing vital signs such as respiration rate, heart sounds and even blood pressure. The device’s accelerometer makes it possible to retrieve information on the user’s mobility with the same chip that performs ECG, as well as to remove motion artefacts to improve the signal quality.
The design has been conceived as a platform that can host different sensor content, so that optical sensors, ultrasound or body temperature can be used to measure other health indicators, depending on the specific application of interest.
Embedded intelligence in smart skin patches enables functions such as anomaly pattern detections in ECG, anomaly pattern classifications in ECG, and user activity classification through motion MEMS with finite state machine and machine-learning cores.
STMicroelectronics’ board design for skin patches using snap electrodes and dry electrodes from DuPont Healthcare
Remote monitoring requires a wireless transmitter, power management, sensing and control units. When the patch is positioned close to the heart through external wet or dry electrodes, a vertical analogue front-end inside the biosensor is able to detect biopotentials that are processed using a dual-core microcontroller and the data can be transmitted wirelessly or by wires for analysis. A wireless charger allows the battery to be charged.
Engineers have also developed a mobile web app to record and visualise data from the e-skin patch, which shows the two single channels.
The biosensor has been used in prototyping the Liveo Smart Biosensing Patch from DuPont Healthcare.
Introducing gyrocardiography
Gyrocardiography (GCG) is a non-invasive technique for assessing heart motions by using a gyroscope sensor to detect angular motion.
Annotation of underlying fiducial points in GCG is presented and compared to opening and closing points of heart valves measured by a pulse wave Doppler. The GCG signal also provides temporal information on the systolic and early diastolic peak velocities of the myocardium.
A 2017 study at the University of Finland described the technique as “a promising mechanical cardiac monitoring tool that enables quantification of beat-by-beat dynamics of systolic time intervals related to hemodynamic variables and myocardial contractility”.
