Description:
Scale bars, 5 mm (top left), 1 mm (top right and middle left), and 3 mm (bottom left and right).
Background
The field of biomedical sensing has long faced challenges in achieving reliable monitoring of muscle activity within dynamic tissue environments. Conventional microelectrode arrays and surface electrodes often struggle with mechanical instability, high impedance, and inadequate conformity to muscle tissues, resulting in inconsistent signal quality. Rigid electrodes can cause tissue damage over time, while flexible surface electrodes lack the necessary penetration depth for precise intramuscular recordings. These limitations hinder advancements in neuroprosthetics, rehabilitation monitoring, and biofeedback applications, creating a need for a sensing technology that can seamlessly integrate with moving biological tissues while maintaining high signal fidelity.
USC Solution
USC researchers have developed a highly stretchable microneedle electrode array designed to achieve reliable, high-quality intramuscular EMG recordings in dynamic tissue environments. It consists of conical polyimide microneedles with a high Young’s modulus of 6.6 GPa, ensuring effective tissue penetration without structural failure. The electrodes are connected via serpentine metallized interconnects made of chromium and gold, embedded within a silicone elastomer substrate that enables stretchability up to 60–90% strain. A novel gel-based etching process precisely defines the active recording zones, and electrodeposition of nanoporous platinum black on the gold tips significantly lowers impedance, enhancing signal fidelity. This combination of advanced microfabrication and materials engineering enables stable, repeatable, and minimally invasive intramuscular sensing.
Benefits
- Reliable performance under dynamic muscle movements
- Low impedance and high signal-to-noise ratio
- Individually-customizable microneedle electrode geometries
- Flexible microneedles reduce tissue damage
- Minimally invasive design supports long-term biomedical use
Key References
Zhao et al. Highly stretchable and customizable microneedle electrode arrays for intramuscular electromyography. Science Advances 10, 18 (2024). https://doi.org/10.1126/sciadv.adn7202