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Hardware Engineer
We implemented a prototype demo integrated magnetic sensor array, microchips, shielded layer and battery etc. into a wearable device for continuous monitoring MMG of the human muscle to work complementary with existing EMG sensors. We pursued the non-invasive on-skin clinical testing with healthy human subjects (5-10) who volunteered for the study and signed informed consent and ethical approval.
We demonstrated an experimentally proof of concept and small scale prototype built in a laboratory environment. Our prototype offers a small footprint, excellent sensitivity, ultralow noise, and high spatial resolution for recording muscle activities. This new miniaturised magnetic sensing system will replace the bulky, invasive and expensive laboratory instruments with easy-to-use wearable platforms.
We showed, for the first time, identification, characterization and quantification of the MMG signals at room temperature by utilising highly miniaturised and sensitive magnetic sensors. The sensor array was precisely placed on the hand skin of the abductor pollicis brevis muscle to record the lateral component of the magnetic signal. The signal-to-noise ratio is over 20 among all the bandpass frequencies.
We developed a real-time measurement system including a large array of sensors and an on-chip analog front-end to realise signal amplification, filtering, noise and drift cancellation. We also designed a dynamic geomagnetic field cancellation technique to reduce noise sources such as the acoustic noise and disturbances of magnetic and electric fields from the earth and surrounding equipment.
We optimised the performance and size of the muscle sensors. According to finite-element analysis and experiment outcomes, the best overall noise performance is obtained with large arrays of large-area sensors. In addition, we introduce a low-profile magnetoelectric sensor with analogue frontend circuitry that has the sensitivity to measure pico-Tesla MMG signals at room temperature.
We developed a finite-element method model of muscle sensors and evaluated its performance of the sensitivity and linearization range. It provided a reliable benchmark for modelling future hybrid magnetic-CMOS developments. We believe that this structure can offer a platform to develop ultra-sensitive, smart and scalable sensors for muscle sensing.
Magnetomyography (MMG) is the study of muscle function through the inquiry of the magnetic signal that a muscle generates when contracted, first formally proposed in 1972. Within the last few decades, extensive effort has been invested to identify, characterise and quantify the MMG signals. However, it is still far from miniaturised, sensitive, inexpensive and low-power muscle sensors.