Octopus-inspired skin-adhesive sensors

(Nanowerk News) Wearable and skin-attachable electronics are becoming part of smart health-care monitoring devices or systems. An essential component of many of these systems are strain or pressure sensors to measure various human activities, including not only human physiological signals such as wrist pulse, heartbeat, and electrocardiography (ECG) but also body motions (e.g., finger, elbow, face, knee, etc.) and subtle skin vibrations.
For real-life usage of these applications, the sensors are required to exhibit a significantly large electrical change with applied strain over a wide sensing range. Furthermore, the sensors should be lightweight, thin, stretchable, simple, and cost-effective fabrication, as well as conformably adherent to the human skin without skin damage after detachment.
In developing these flexible and wearable sensors, researchers have experimented with various nanomaterials such as nanoparticles, nanowires, nanofibers, carbon nanotubes, and graphene as sensing materials.
Among them, in particular graphene-nanoparticle-based percolation systems are attractive candidates because they are based on easy and facile solution processes, as well as having unique material properties such as extraordinary mechanical strength with flexibility, good electrical conductivity, and chemical stability.
In recent work reported in ACS Applied Materials & Interfaces ("Water-Resistant and Skin-Adhesive Wearable Electronics Using Graphene Fabric Sensor with Octopus-Inspired Microsuckers"), researchers in Korea demonstrate a facile, low-cost, scalable fabricating method for water-resistant and skin-adhesive wearable graphene-coated fabric (GCF) sensors.
Fabrication and characterization of graphene-coated fabric sensors
Fabrication and characterization of GCF sensors. (a) Schematic illustration of the graphene-coated fabric (GCF) fabrication process. The octopus-inspired microsucker structures are patterned on the rGO fabric. (b, c) Scanning electron microscope (SEM) images of (b) rGO fabric sample with coating of rGO-PDMS composite for conductive passivation and (c) OP-engraved rGO fabric. (Reprinted with permission by American Chemical Society) (click on image to enlarge)
These GCF sensors with graphene particles are thin, lightweight, highly conductive, and stretchable. The resulting GCF sensor exhibits sensitive responses to statically and dynamically applied strains with low detection limits and has reliable responses to reproducible operations for both lateral and vertical strains.
Inspired by octopus-inspired microsuckers, patterns on the side of the fabric that touches the skin allow strong adhesion forces on the skin surface, which may be dry/wet and rough.
With these sensors, team demonstrated the monitoring of a full range of human activities on the human skin, including human physiological signals such as wrist pulse and electrocardiography (ECG) as well as body motions and speech vibrations.
They demonstrated simultaneous measurements of ECG and wristbending motion in dry and wet conditions with continuous bending motions, enabled by skin adherence and wet resistance properties.
This study has opened up the possibility of wearable and skin-adherent electronic fabric sensors working in harsh environments including wet or underwater conditions for various future medical applications.
By Michael is author of two books by the Royal Society of Chemistry: Nano-Society: Pushing the Boundaries of Technology and Nanotechnology: The Future is Tiny.
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