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The advancement of engineered mechanisms for harvesting mechanical energy from the body and converting it into electricity holds significant importance in the realm of bioelectronics. This technology presents a promising avenue for powering miniaturised biomedical devices like cardiac pacemakers, brain stimulators, and wearable drug delivery systems.
Over the past decade, numerous proposals have surfaced regarding miniaturised mechanoelectrical converters. However, the primary challenge lies in achieving both high electrical output and body-conformal device structures simultaneously.
Addressing this challenge, a research team spearheaded by Professor Lizhi Xu from the Department of Mechanical Engineering at the University of Hong Kong (HKU) has developed a groundbreaking mechanoelectrical energy converter utilising hydrogels, a class of water-rich soft polymeric materials.
Central to their innovation is the utilisation of ion-loaded hydrogels positioned between two electrodes to construct the electric generator. Professor Xu underscores the significance of structural and chemical asymmetry in amplifying the separation of charges within the ion-loaded hydrogel. This asymmetry is pivotal in enhancing the electrical output of the hydrogel generators by orders of magnitudes, thereby facilitating the effective powering of miniaturised biomedical devices.
When mechanical compression is applied to the device, the positively and negatively charged ions within the hydrogel move at different rates, leading to the generation of voltage and current due to the separation of electric charges.
Leveraging asymmetric designs within the device, the research team succeeded in significantly enhancing the electrical output, achieving unprecedented levels of 5.5mA/m2 and 916 mC/m2 per cycle. This surpasses the performance of other systems by approximately tenfold, including triboelectric nanogenerators and other flexible generators.
Hydrogels present an ideal candidate for body-conformal device structures due to their soft, flexible nature and ability to mimic the properties of biological tissues. Additionally, they boast high biocompatibility and can conform to various tissue shapes within the body. Professor Xu emphasises the potential applications of this technology in biomedical devices such as cardiac pacemakers, wearable health monitors, VR/AR interfaces, and more.
In a demonstration within the study, a soft patch for controlled drug release was showcased, illustrating the versatility of this technology in therapeutic applications. With its publication in Nature Communications under the title “A high-current hydrogel generator with engineered mechanoionic asymmetry,” the research marks a significant milestone in the advancement of mechanoelectrical energy conversion technology, promising transformative impacts in the field of bioelectronics.
The Bioelectronics Market, valued at US$7.77 Billion in 2022, is anticipated to reach US$13.86 Billion by 2030, with a projected CAGR of 11.3% from 2023 to 2030. Its expansion is attributed to advancements in surface chemistry, semiconductor technology, and the fusion of artificial and biological devices to enable applications in prostheses, disease detection, and prevention.
Market growth is expected to outpace the average, propelled by increasing cardiovascular disease rates and the widespread adoption of artificial pacemakers. Rising awareness about bioelectronics is a key factor driving expansion. Technological advancements like nanoscale electrical measurement devices for proteomics and genomics, aiding in protein function determination and cellular reaction pathway analysis, are set to further fuel industry growth over the next seven years.
Additionally, the market is poised to benefit from growing research and development initiatives focusing on point-of-care micro-flow and micro-chemical cytometry, tools for identifying and isolating rare circulating tumour cells, massive parallel micro-fluidics immunoassays, and point-of-care metabolism analysis. However, challenges such as the high cost of modern bioelectronics devices and the requirement for high-resolution imaging technologies in rural areas hinder market growth.