Capacitive biosensors are an emerging technology revolutionizing wearable sensing systems and personal healthcare devices. They are capable of continuously measuring bioelectrical signals from the human body while utilizing textiles as an insulator. Different textile types have their own unique properties that alter skin-electrode capacitance and the performance of capacitive biosensors. This paper aims to identify the best textile insulator to be used with capacitive biosensors by analysing the characteristics of 6 types of common textile materials (cotton, linen, rayon, nylon, polyester, and PVC-textile) while evaluating their impact on the performance of a capacitive biosensor. A textile-insulated capacitive (TEX-C) biosensor was developed and validated on 3 subjects. Experimental results revealed that higher skin-electrode capacitance of a TEX-C biosensor yields a lower noise floor and better signal quality. Natural fabric such as cotton and linen were the two best insulating materials to integrate with a capacitive biosensor. They yielded the lowest noise floor of 2 mV and achieved consistent electromyography (EMG) signals measurements throughout the performance test.

Remote healthcare monitoring (RHM) is an emerging trend in the biomedical field that leverages on the advancement of Internet of Things (IoT) to enhance the coverage of healthcare services around the world. An RHM system with the electromyography (EMG) measurement capability has great potential in improving the efficiency of medical treatment and physical therapy for chronic inflammatory myopathies. Conventional EMG measurement is often invasive, complex and require an ever-present medical officer. This paper proposes a capacitive electromyography (CEMG) monitoring system to overcome the limitations of the contact EMG monitoring system by using the capacitive sensing methodology. The system architecture and circuit design are detailed in this paper and the hardware implementation with experimental results are presented. This CEMG monitoring system achieved extremely low noise floor of less than 2 mV. Its performance also highly correlates with the conventional wet contact electrode without requiring any post signal processing. Therefore, this CEMG monitoring system is ideal for remote healthcare monitoring applications.

Musculoskeletal diseases and disorders (MSDs) have a significant negative impact on personal health and the worldwide economy. Leveraging the advancement of wearable sensing technology to provide electromyography (EMG) measurement capability can improve the efficiency of the public healthcare strategy to combat MSDs. Integrating conventional EMG contact electrodes into a wearable device is proven to be a challenge because it requires direct electrical contact with the body and has a dependency on the conductive gel. Existing prototypes of capacitive electromyography (cEMG) sensors are typically large and designed with a hybrid printed circuit board. This research paper presents a fully flexible cEMG biomedical sensor with integrated front-end analog circuitry in only a medical plaster size. An efficient moving average squared (MASq) technique is presented to effectively suppress the noise floor and improve the signal quality. The experimental results of measuring EMG signals from flexor carpi radialis, extensor carpi radialis, and biceps brachii using the flexible cEMG biomedical sensor are presented. The post-process data recorded signal-to-noise ratios ranging from 1.8 – 5.7 while achieving practically 100% sensitivity in measuring muscle contractions. Its miniature, rugged, and flexible characteristics allow it to operate as a standalone adhesive plaster sensor or integrate into wearable applications.

A capacitive electromyography (cEMG) biomedical sensor measures the EMG signal from human body through capacitive coupling methodology. It has the flexibility to be insulated by different types of materials. Each type of insulator will yield a unique skin–electrode capacitance which determine the performance of a cEMG biomedical sensor. Most of the insulator being explored are solid and non-breathable which cause perspiration in a long-term EMG measurement process. This research aims to explore the porous medical bandages such as micropore, gauze, and crepe bandage to be used as an insulator of a cEMG biomedical sensor. These materials are breathable and hypoallergenic. Their unique properties and characteristics have been reviewed respectively. A 50 Hz digital notch filter was developed and implemented in the EMG measurement system design to further enhance the performance of these porous medical bandage insulated cEMG biomedical sensors. A series of experimental verifications such as noise floor characterization, EMG signals measurement, and performance correlation were done on all these sensors. The micropore insulated cEMG biomedical sensor yielded the lowest noise floor amplitude of 2.44 mV and achieved the highest correlation coefficient result in comparison with the EMG signals captured by the conventional wet contact electrode.

This letter presents the optimum value of skin-electrode capacitance for a capacitive electromyography (CEMG) biosensor design. Skin-electrode capacitance is proved to be an important variable when defining the input characteristic of a capacitive biosensor by an electrical model of skin-electrode interface. The experimental results show that a CEMG biosensor with the skin-electrode capacitance range of between 255 and 340 pF yields the best performance, low noise, and is small in size.

Transforming existing electromyography (EMG) measurement system into portable and wearable devices is key to fuel the revolution of digital healthcare and rehabilitation. Conventional EMG measurement systems that rely on invasive needle electrodes and noninvasive wet and dry contact electrodes are impractical to telehealth applications. Existing capacitive EMG (cEMG) measurement systems presented by various research groups are typically designed with multistage analog front-end circuitry and complex data acquisition (DAQ) systems. This article proposed a simple and versatile multichannel wireless cEMG measurement system. It consists of flexible cEMG biomedical sensors, a low-noise wireless DAQ module, and a moving average of the squared (MASq) data signal processing techniques. The proposed flexible capacitive biomedical sensor can be insulated by porous and nonporous materials. Only two electrodes are needed to acquire raw EMG signals while achieving low-common-mode noise. Overall, the system achieves a high-mean pulse signal-to-noise ratio (PSNR) of 13.6 (polyimide film) and 8.3 (micropore). It recorded a linear correlation between the mean root-mean-square (RMS) of the MASq data and muscle strength with a step size of 1 kg. The total power consumption of this system is 41 mW with five EMG input channels, averaging 8 mW each. This low-noise and low-power consumption characteristic is ideal for battery-based wearable devices.