Gelatin-Based Metamaterial Hydrogel Films with High Conformality for Ultra-Soft Tissue Monitoring.

Highlights: Novel customized metamaterial gelatin-based conductive film (GCF) was developed to ensure good biocompatibility and biodegradability for implantable bioelectronics integrating monitoring with tissue repair. The metamaterial property demonstrated high conformal with soft tissues to promote the signal-to-noise ratio. The GCF revealed elastic modulus regulated from 20 to 420 kPa and Poisson's ratio from − 0.25 to 0.52. It was fabricated by embedding different 3D printing ultrafine fiber networks with metamaterial design into ultra-low modulus Gelatin methacryloyl hydrogel. Implantable hydrogel-based bioelectronics (IHB) can precisely monitor human health and diagnose diseases. However, achieving biodegradability, biocompatibility, and high conformality with soft tissues poses significant challenges for IHB. Gelatin is the most suitable candidate for IHB since it is a collagen hydrolysate and a substantial part of the extracellular matrix found naturally in most tissues. This study used 3D printing ultrafine fiber networks with metamaterial design to embed into ultra-low elastic modulus hydrogel to create a novel gelatin-based conductive film (GCF) with mechanical programmability. The regulation of GCF nearly covers soft tissue mechanics, an elastic modulus from 20 to 420 kPa, and a Poisson's ratio from − 0.25 to 0.52. The negative Poisson's ratio promotes conformality with soft tissues to improve the efficiency of biological interfaces. The GCF can monitor heartbeat signals and respiratory rate by determining cardiac deformation due to its high conformability. Notably, the gelatin characteristics of the biodegradable GCF enable the sensor to monitor and support tissue restoration. The GCF metamaterial design offers a unique idea for bioelectronics to develop implantable sensors that integrate monitoring and tissue repair and a customized method for endowing implanted sensors to be highly conformal with soft tissues. [ABSTRACT FROM AUTHOR]