In a study published in the journal ACS Applied Polymer Materials, by incorporating silver nanoparticle-covered graphene oxide (Ag/TA@GO)-based nanomaterials into a polyacrylamide (PAM) hydrogel framework, researchers created a multipurpose nanoscale composite hydrogel with exceptional ductility, resistance to wear, and electric conductance.
Study: Highly Stretchable, Sensitive, and Durable Ag/Tannic Acid@Graphene Oxide-Composite Hydrogel for Wearable Strain Sensors. Image Credit: metamorworks/Shutterstock.com
What are Flexible Electronic Sensors
Pliable sensory electronics have recently become a key study area in applications of electronics, personal health tracking devices, and human-machine interaction.
The pliable electronic sensor is an integral part of sensory skin and soft robotics, converting environmental inputs such as temperature, pressure, and moisture into measurable electrical impulses.
One of the most rapidly developed and commonly used flexible electronic sensors is the elastic wearable strain gauge. Elastic wearable sensing devices with design flexibility and rapid detecting responses may be mounted on garments or adhered directly onto human skin. This can be done to accomplish continuous monitoring of relevant motion and physiological functions including bending of joints, speech, respiration, pulse, and body temperature.
Pliable electronic gadgets must have certain fundamental characteristics along with good efficiencies, such as high tensile strength, elasticity, longevity, minimal energy consumption, and biocompatibility.
Advantages of Using Graphene Oxide
Lately, the addition of natural or synthetic fillers such as cellulose, silicon, and carbon nanotubes has been recognized as a straightforward and effective means of improving the mechanical properties of hydrogels.
Owing to their many intriguing features, graphene and graphene oxide (GO) are the most important 2D carbonaceous nanomaterials.
GO, in particular, is a layered sp2-bonded carbon with the ability to connect complex functional groups like epoxy, carboxyl, and hydroxyl groups to its faces.
As opposed to graphene, GO shows good stability in a wide range of solutions while retaining many of its properties, such as strong hydrophilic nature, vast specific area, high elastic modulus and strength, low density, cytocompatibility, electrical conductance, and strong heat conduction.
Because of these enhanced properties, GO is compliant with other materials such as colloids, polymers, films, and amphiphilic chemicals, and it may serve as a significant component in the construction of diverse supramolecular complexes.
Scientists have been particularly engaged in investigating electronic sensory devices, energy batteries, and composites based on GO owing to its excellent mechanical capabilities and electrical conductance.
Incorporation of Graphene Oxide into PAM Hydrogel
The hydrogel contains a three-dimensional polymer framework and has lately received a lot of interest owing to its wide range of uses as an excellent medium for elastic wearable sensors.
Composite hydrogels, as opposed to standard hydrogels, often have better optic, mechanical, and expansion capabilities and may transcend the limits of one-component chemically cross-linked hydrogels.
These nanoscale composite hydrogels integrate the benefits of nanotechnology and 3D hydrogels, such as soft texture, cytocompatibility, pH reactivity, and electric responsiveness, which are useful in the domains of flexible sensing devices and human-machine contact.
Congesting those synthetic nanoparticles, on the other hand, has negative consequences such as weak mechanical characteristics and loss of biocompatibility, and might eventually compromise the effectiveness of composite hydrogels, restricting the uses of these nanocomposite hydrogels.
GO, as it turns out, may be employed as a nanocomposite additive in the manufacture of a GO composite hydrogel. The impact of introducing GO is mostly apparent in improved mechanical qualities (strength and elasticity) and expanded stimulus-response types (pH and photothermal reaction, and self-healing).
As a result, incorporating GO into the hydrogel is emerging as a new study topic in the field of GO composites.
Important Findings and Future Outlook
In this study, by interconnecting Ag/TA@GO structures with a PAM aerogel, the team were able to create a versatile biomimetic composite hydrogel.
The presence of evenly distributed Ag/TA@GO nanoscale compounds aided in the creation of an optimal 3D conducting framework in Ag/TA@GO-PAM hydrogels. As a result, the hydrogel demonstrated exceptional electrical and mechanical characteristics, and the elastic strain gauge built on the hydrogel exhibited a broad detection spectrum while fulfilling strain responsiveness, consistency, and robustness.
Furthermore, the hydrogel-based strain gauge could recognize a range of human body movements instantaneously, as well as face detection and voice recognition.
The hydrogel was particularly suitable for generating electronic skin that mimicked human hands to handle a mobile phone, indicating a wide applicability promise in bionic robotics. Furthermore, the hydrogel might be built as a pressure gauge for information encrypting and communication and recognition using International Morse Code.
As a result, this hydrogel has the benefits of quick reaction, responsiveness, and high accuracy for human monitoring and might be viable for AI uses such as electronic skin, human-robot contact sensors, and data encrypting sensors.
Chen, K., Wang, F., et al. (2022). Highly Stretchable, Sensitive, and Durable Ag/Tannic Acid@Graphene Oxide-Composite Hydrogel for Wearable Strain Sensors. ACS Applied Polymer Materials. Available at: https://pubs.acs.org/doi/10.1021/acsapm.1c01880