Metalon JS-ADEV ET010 Silver Nanoparticle Ink Enables a Highly Conformable and Ultrasound-Transparent Patch for Advanced Neuromuscular Monitoring
The field of wearable medical devices is constantly pushing the boundaries of what’s possible, especially in areas like neuromuscular monitoring. A recent publication in IEEE Transactions on Neural Systems and Rehabilitation Engineering highlights a significant leap forward with the introduction of ReGrid, a novel high-density electromyography (HD-sEMG) dry electrode grid. This innovative patch is designed to be highly conformable to the skin and, crucially, fully transparent to ultrasound, enabling simultaneous HD-sEMG and ultrasound imaging. At the heart of this breakthrough is NovaCentrix’s Metalon JS-ADEV ET010 silver nanoparticle ink, which played a pivotal role in realizing ReGrid’s unique capabilities.
Developed by researchers at the Politecnico di Torino, in Turin, Italy.G. L. Cerone, T. Vieira, M. Gazzoni, and A. Botter, ReGrid addresses long-standing challenges in integrated neuromuscular assessment. By combining high-quality sEMG detection with real-time ultrasound imaging, researchers can gain unprecedented insights into muscle function, architecture, and tissue motion. This advancement promises to revolutionize how we study and diagnose conditions related to muscle activity, offering a versatile tool for both clinical and research applications.
Why Integrated Neuromuscular Assessment Matters
Traditional HD-sEMG grids often suffer from limitations in conformability, especially on curved body surfaces, leading to poor electrode-skin contact, motion artifacts, and power line interference. Furthermore, the presence of standard electrode grids can significantly hinder or distort ultrasound imaging, making simultaneous acquisition challenging or impossible without compromising signal quality or requiring complex, impractical setups. The ability to concurrently acquire high-quality HD-sEMG signals and ultrasound images from the same muscle region is critical for a comprehensive understanding of electromechanical muscle properties.
ReGrid directly tackles these issues by offering a thin-film, flexible, and acoustically transparent solution. This integrated approach allows for a more complete characterization of muscle contraction, including the relationship between neural drive, tissue motion, and architectural changes, all from a single, minimally intrusive device. Such capabilities are essential for advancing research into motor control, rehabilitation, and sports science, as well as for developing more effective diagnostic and therapeutic strategies.
The Role of NovaCentrix Metalon JS-ADEV ET010 Silver Nanoparticle Ink
The innovative design of ReGrid relies heavily on the advanced material properties and processing compatibility of NovaCentrix’s Metalon JS-ADEV ET010 silver nanoparticle ink. This ink was instrumental in fabricating the conductive elements of the patch, which were inkjet-printed directly onto a 15 µm-thick polyurethane (PU) membrane. This direct printing method is a cornerstone of ReGrid’s design, enabling its thin profile and high conformability.
The choice of a PU membrane as a support layer was driven by its inherent ultrasound transparency and compatibility with inkjet printing technology. The Metalon ink allowed for the precise deposition of silver nanoparticle-based conductive traces and electrodes, which were then baked at 150°C for 15 minutes as recommended by NovaCentrix. This process eliminated the need for vacuum processing, photolithography, or expensive cleanroom infrastructure, making the fabrication scalable and cost-effective. By printing directly onto the ultrasound-transparent material, the researchers avoided the need for cavities in the supporting material, thereby significantly reducing the overall thickness of the grid and ensuring its full transparency to ultrasound.
Enabling Unprecedented Performance in Wearable Sensing
The combination of ReGrid’s design and the properties of the NovaCentrix ink resulted in a device with exceptional performance characteristics:
- Superior Conformability: Bench tests demonstrated that ReGrid adhered perfectly to curved surfaces with radii of 41 mm, 57 mm, and 78 mm, exhibiting no missing electrical contacts. This is a significant improvement over standard grids, which showed 2 to 15 missing contacts under similar conditions.
- Full Ultrasound Transparency: Both in-vitro and in-vivo tests confirmed ReGrid’s transparency to ultrasound. Image quality with ReGrid positioned between the probe and a phantom was comparable to direct probe placement, with a contrast-to-noise ratio (CNR) of 5.7 dB for ReGrid versus 4.8 dB for the reference. In-vivo measurements on the tibialis anterior muscle revealed clear anatomical structures without artifacts, even with the ultrasound probe placed directly over the EMG electrodes.
- Stable Electrical Performance: ReGrid exhibited electrode-skin impedance magnitude at 50 Hz (11.18 ± 2.89 kΩ·cm²) and input-referred electrode-skin noise (2.0 ± 1.1 µVrms) comparable to state-of-the-art electrode grids. Crucially, these electrical characteristics remained stable over 60 minutes, even with water-based ultrasound gel applied, indicating the electrode system’s impermeability to external agents and robust signal quality.
- High-Quality HD-sEMG Signals: The presence of the ultrasound probe over the electrodes did not significantly affect the quality of detected HD-sEMG signals, including conduction velocity (CV) estimates (3.50 ± 0.02 m/s with US vs 3.49 ± 0.02 m/s without US), signal-to-noise ratio (SNR), or power line interference. Single motor unit analysis also showed that decomposition results were unaffected by the ultrasound probe.
Expanding the Horizon of Neuromuscular Research
The development of ReGrid, enabled by NovaCentrix ink, opens up a new generation of possibilities for neuromuscular research and wearable medical devices. The ability to acquire high-quality HD-sEMG signals and ultrasound images concurrently from the same muscle region allows for a more holistic understanding of muscle function. This technology facilitates the characterization of electromechanical properties, including the intricate relationships between neural drive, tissue motion, and architectural changes within muscles.
Furthermore, ReGrid’s full ultrasound transparency paves the way for advanced imaging techniques, such as three-dimensional muscle imaging through moving the US probe over the electrodes or using 2D matrix array transducers for volumetric reconstructions. Its waterproof nature also expands the potential for EMG investigations in aquatic environments, broadening the scope of muscle function studies. The scalable design, allowing for different electrode configurations and higher-density layouts (e.g., 5 mm IED), ensures its adaptability to various application requirements, making ReGrid a versatile platform for future innovation in biopotential sensing.
NovaCentrix: Enabling the Future of Printed Electronics
This study is a testament to the power of advanced conductive materials in enabling cutting-edge research and product development. NovaCentrix is proud to see our Metalon inks contributing to such significant advancements in medical wearables and neuromuscular diagnostics. Our commitment to developing high-performance, reliable, and versatile conductive inks empowers researchers and innovators to overcome existing limitations and create the next generation of smart, flexible, and integrated electronic devices. We look forward to continuing our support for the scientific community as these technologies move closer to widespread adoption and clinical impact.
Read the full paper: Cerone, G. L., Vieira, T., Gazzoni, M., & Botter, A. (2026). ReGrid: a highly conformable and ultrasound transparent patch for HD-sEMG detection. IEEE Transactions on Neural Systems and Rehabilitation Engineering, 34.