Ultrasoft and Biocompatible Magnetic-Hydrogel-Based Strain Sensors for Wireless Passive Biomechanical Monitoring

Abstract

Implantable flexible mechanical sensors have exhibited great potential in health monitoring and disease diagnosis due to continuous and real-time monitoring capability. However, the wires and power supply required in current devices cause inconvenience and potential risks. Magnetic-based devices have demonstrated advantages in wireless and passive sensing, but the mismatched mechanical properties, poor biocompatibility, and insufficient sensitivity have limited their applications in biomechanical monitoring. Here, a wireless and passive flexible magnetic-based strain sensor based on a gelatin methacrylate/Fe3O4 magnetic hydrogel has been fabricated. The sensor exhibits ultrasoft mechanical properties, strong magnetic properties, and long-term stability in saline solution and can monitor strains down to 50 μm. A model of the sensing process is established to identify the optimal detection location and the relation between the relative magnetic permeability and the sensitivity of the sensors. Moreover, an in vitro tissue model is developed to investigate the potential of the sensor in detecting subtle biomechanical signals and avoiding interference with bioactivities. Furthermore, a real-time and high-throughput biomonitoring platform is built and implements passive wireless monitoring of the drug response and cultural status of the cardiomyocytes. This work demonstrates the potential of applying magnetic sensing for biomechanical monitoring and provides ideas for the design of wireless and passive implantable devices.

Core–Shell Droplet-Based Microfluidic Screening System for Filamentous Fungi

“…Screening of mycelial forms of filamentous fungi using FADS requires a long and stable culture for accurate analysis. Gel-MA is a highly biocompatible material that has been used in cell culture and tissue engineering. , This study demonstrated that core–shell droplets of Gel-MA material can support the entire growth process of A. niger for up to 2 days, including spore germination and mycelial extension, which is a more accurate representation of the actual fermentation process of A.…”

“…Gel-MA is a highly biocompatible material that has been used in cell culture and tissue engineering. 25,34 This study demonstrated that core−shell droplets of Gel-MA material can support the entire growth process of A. niger for up to 2 days, including spore germination and mycelial extension, which is a more accurate representation of the actual fermentation process of A. niger. The present results suggest that spores grow faster inside the droplet than inside the flask, which is consistent with a previous report.…”

Recent Advances in Nanomaterials Used for Wearable Electronics

“…Examples of transducers encompass temperature [ 82 , 83 ], pressure/strain [ 84 , 85 ], and ion concentration transducers, among others. Recently, Qi Zhang et al introduced a magnetic-hydrogel-based soft strain transducer that exploits the relative magnetic field changes of a gelatin methacrylate (GelMA)/Fe 3 O 4 magnetic hydrogel film, as illustrated in Figure 5 a [ 86 ]. This material exhibits excellent magnetic properties (12.74 emu/g), great biocompatibility, desired stability, and a very low Young’s modulus that renders it ultrasoft.…”

“… ( a ) A strain transducer based on (GelMA)/Fe 3 O 4 –magnetic hydrogel film (reprinted with permission from Ref. [ 86 ], Copyright 2022 American Chemical Society). ( b ) A pressure transducer array made of graphene nanoparticles (reprinted with permission from Ref.…”

Recent development of conductive polymer composite‐based strain sensors

“…As a material that directly contacts human skin, the biocompatibility is a key issue to be considered in designing wearable strain sensors. 117 For instance, Xu et al 118 have fabricated a capacitive strain sensor composed of ionic hydrogel and silver nanofibers (AgNFs). The sensor showed no skin irritation even after the volunteer wore the sensor for 4 days, exhibiting excellent biocompatibility (Figure 11A).…”