Radar-based sensors can be used to monitor harsh environments that current technology cannot adapt to. The system is resilient against extreme adverse conditions, such as extreme temperatures, high salinity, varying pressure, intense radiation, reactive chemicals, and/or high humidity.  

Graphene is an interesting form of carbon, consisting of layers of interconnected hexagonal rings of carbon atoms. This structure has special physical and electronic properties, with potential for various applications.

Graphene has been predicted to be a miracle material for many years, but its applications in harsh environmental conditions have not yet been developed. Existing sensor technologies operate under very limited environmental conditions and will fail or become unreliable if deviations are significant.

Sheikh collaborated with Muhammad Hussain from King Abdullah University of Science and Technology (KAUST) to design the new sensor.

The new powerful sensor relies on changes in the resistance of graphene due to acidity, temperature fluctuations, and the salinity of the solution (measured in pH). The system can track additional variables, such as pressure and water flow.

The team pointed out that sensing multiple variables can be integrated into a single device, greatly enhancing its practicality.

Graphene is placed on a flexible polyimide polymer substrate and can be linked to suitable electronic systems to collect and transmit signals for tracking environmental variables. The resulting information can then be sent wirelessly using standard Bluetooth technology.

System resilience is the most significant practical advancement. This resilience allows the system to withstand temperatures up to 650°C, as well as intense radiation, varying pressure, high salinity, high humidity, reactive chemicals, or any combination of these conditions.

Furthermore, these sensors offer advantages in sensitivity; for example, their sensitivity in temperature sensing is improved by 260% compared to existing sensors.

Our research definitively demonstrates for the first time the potential of graphene as a sensing material under various harsh environmental conditions.

Muhammad Hussain, King Abdullah University of Science and Technology

Potential real-world applications include monitoring body fluids, seawater, space exploration, conditions in the oil and gas sector, and several scenarios involving exposure to chemicals that would damage existing sensors.

The thin profile and flexibility of the new sensor also make it suitable for wearable technology or medical applications for athletes and divers.

The team believes that the ongoing development connecting electronic devices with the Internet of Everything (IoE) and Internet of Things (IoT) technologies will bring diverse demands and opportunities for their robust and flexible sensors.

Further Reading

What is a graphene sensor?

As the name suggests, a graphene sensor is a sensor that uses graphene as the active sensing material or sensing surface. Graphene has become an efficient sensing surface for many reasons, and its sensing properties are currently widely used in various sensors, from strain gauges to biosensors, and are now beginning to be commercially produced. Here, we take a deeper look at why graphene has the potential to disrupt a very mature industry. Sensors rely on an active material to respond to conditions in a given environment. The way the active material works, and how it detects and senses selected parameters in a given environment, varies by sensor type. This can take the form of stretching the material (such as in stress/strain gauges) to detect gaseous molecules or even temperature changes. Regardless of how the parameter is sensed, there must be a change in the active material, i.e., an active response, and this response must be detectable and readable by surrounding components. When the stimulus interacts with the material, this active response usually takes the form of a change in conductivity across the material.

Types of graphene sensors？

When we talk about "graphene sensors," there is no single type; the versatility of graphene means it can be used in almost every sensor type. Its inherent thinness provides an excellent surface for interaction with molecules, and because it has such high electronic conductivity and charge carrier mobility, it can even detect changes in the conductivity of the entire graphene sheet (due to stimulus interaction), which is very high. Graphene sensors can achieve high sensitivity.

In addition, graphene has a relatively large specific surface area, meaning it has a larger relative sensing area compared to other materials. Overall, this means that using graphene allows for the detection of lower concentrations of molecules compared to other materials. This ability to be sensitive to the smallest concentrations of molecules encountering the graphene sensing surface makes graphene suitable for gas, volatile organic compound (VOC), humidity sensors, and various biosensors (for measuring glucose, DNA, and proteins, etc.).

Beyond these basic properties, graphene is thermally conductive and very stable at high temperatures, so it has been applied in temperature sensors. Graphene also has very high mechanical strength and the ability to bend under strain without breaking. After the stimulus is removed, graphene will also return to its original orientation. These properties have led to the development of various pressure, stress, strain, piezoelectric, and piezoresistive sensors.

In practice, all forms of graphene have been used, from single-layer and few-layer non-functionalized graphene to graphene oxide, reduced graphene oxide, and even more complex structures (such as graphene nanowalls), as well as composite, hybrid, and conjugated graphene materials.

Regardless of the sensor type, graphene-based sensors can be used in many different environments, whether high temperature, high pressure, or harsh chemical environments, because graphene has high stability against all harmful stimuli. Therefore, graphene is not only versatile in the types of sensors it can be used in, but the environments in which graphene-based sensors can be used are also diverse. The combination of these two factors is why graphene-based sensors have great prospects.