Greening the Sensor Industry: Graphene Algae Hydrogels as Alternative to Rubber-Based Materials

Researchers are working to create materials that can imitate the mechanical, electrical, and chemical capabilities of biological molecules as technology develops. Hydrogels, a group of polymers that resemble soft tissues, have recently demonstrated considerable promise in a wide range of applications, including drug delivery and tissue engineering. A unique class of food-inspired hydrogels that can sense pressure changes and have potential applications in many different domains has been introduced in a recent study that was published in ACS Sustainable Chemistry & Engineering.

Piezoresistive Graphene Hydrogels: A New Generation of Sensors

Materials classified as piezoresistive are those whose electrical resistance varies in accordance with induced mechanical stress or strain. In the simplest terms, a piezoresistive material is a useful sensing element because it changes its electrical characteristics when pressed, twisted, or bent. Accelerometers, pressure sensors, human-robot interaction, and other devices all make use of piezoresistive sensors. However, because most piezoresistive materials are rigidly held they cannot be used in purposes that call for soft and flexible sensors.

A potential material for piezoresistive sensors, graphene has good mechanical, electrical, and thermal characteristics. The layer of carbon atoms in graphene is one atom thick and is structured like a honeycomb, making it the thinnest substance ever discovered. Due to graphene’s high conductivity, electrons can move across it effectively and fast. However, because graphene is a two-dimensional material, it is laborious to form it into a structure of three dimensions that can detect a shift in pressure, making graphene-based sensors tough to create.

The features of hydrogels, which can resemble those of biological tissues, make them attractive for a variety of biomedical applications. Hydrogels are soft, water-swelling polymers. The chemical makeup and crosslinking density of hydrogels can be changed to customize the attributes they possess. Hydrogels can be created from polymers that are either natural or synthetic. Engineers have recently coupled hydrogels with graphene to produce new materials that can perceive a variety of stimuli, such as relative humidity, temperature, and visible light.

Inspired by Food: The Birth of Piezoresistive Graphene Hydrogels

The porous and linked natural structures of various foods, like cheese and meat, served as the researchers’ inspiration for this study. By combining graphene oxide sheets with sodium alginate, a natural polymer derived from brown seaweed, the researchers developed piezoresistive graphene hydrogels using a straightforward procedure. The combination was subsequently crosslinked using calcium ions, resulting in a hydrogel with a structure similar to several meals. A promising contender for pressure sensing applications, the subsequently formed hydrogel is supple, malleable, and conductive to electrical currents.

By applying different pressures to the piezoresistive graphene hydrogels and evaluating their electrical resistance, the researchers evaluated their sensing skills. The findings demonstrated that the hydrogels could detect pressure changes across a wide frequency range making them appropriate for sensing a variety of mechanical stimuli. The hydrogels’ stability and toughness were also examined by the researchers, who discovered that they could resist numerous pressure cycles without significantly degrading.

Future Applications of Piezoresistive Graphene Hydrogels

Piezoresistive graphene hydrogels have a wide range of possible applications since these sensors can be utilized in many different contexts. The use of wearable sensors to monitor vital signs is one of the most promising applications. These hydrogels’ softness and flexibility make them perfect for use as sensors since they can adapt to the shape of the body and allow continuous monitoring of heart rate, breathing rate, and other vital signs. Patients who require regular monitoring, such as those with chronic conditions or those recovering from surgery, may find this to be especially helpful.

Piezoresistive graphene hydrogels could also be used as pressure sensors in robotics and human-robot interaction. In this industry, soft and flexible sensors are essential because they can simulate touch and offer a more intuitive and natural user interface. Piezoresistive graphene hydrogels, for instance, could be utilized in robotic hands or prosthetic limbs to enable the user to feel the force and pressure applied by items.

Piezoresistive graphene hydrogels may also be employed as touch sensors in wearable technology, mobile devices, and tablets. These sensors’ supple and adaptable qualities might enable more organic interactions between people and technology, improving their usability. Piezoresistive graphene hydrogels, as an illustration, might be utilized in touch displays to offer haptic feedback, enabling users to interact with the buttons or switches they push.

The Promise of Modern Materials Science

In conclusion, the potential applications of piezoresistive graphene hydrogels are diverse and promising. The soft and flexible nature of these sensors, combined with their excellent sensing capabilities, durability, and stability, make them an attractive candidate for various applications in the fields of biomedicine, robotics, and electronics. As the technology improves and these sensors become more accessible, we can expect to see them used in numerous innovative applications, improving our lives and enhancing our interactions with the world around us.

Study DOI: 10.1021/acssuschemeng.2c06101

Engr. Dex Marco Tiu Guibelondo, BS Pharm, RPh, BS CpE

Editor-in-Chief, PharmaFEATURES