What is a sensor?

A sensor is a device that detects events that occur in the physical environment (like light, heat, motion, moisture, pressure, and more), and responds with an output, usually an electrical, mechanical or optical signal. The household mercury thermometer is a simple example of a sensor - it detects temperature and reacts with a measurable expansion of liquid. Sensors are everywhere - they can be found in everyday applications like touch-sensitive elevator buttons and lamp dimmer surfaces that respond to touch, but there are also many kinds of sensors that go unnoticed by most - like sensors that are used in medicine, robotics, aerospace and more.

Traditional kinds of sensors include temperature, pressure (thermistors, thermocouples, and more), moisture, flow (electromagnetic, positional displacement and more), movement and proximity (capacitive, photoelectric, ultrasonic and more), though innumerable other versions exist. sensors are divided into two groups: active and passive sensors. Active sensors (such as photoconductive cells or light detection sensors) require a power supply while passive ones (radiometers, film photography) do not.

Where can sensors be found?

Sensors are used in numerous applications, and can roughly be arranged in groups by forms of use:

  • Accelerometers: Micro Electro Mechanical technology based sensors, used mainly in mobile devices, medicine for patient monitoring (like pacemakers) and vehicular systems.
  • Biosensors: electrochemical technology based sensors, used for food and water testing, medical devices, fitness tracker and wristbands (that measure, for example, blood oxygen levels and heart rate) and military uses (biological warfare and more).
  • Image sensors: CMOS (Complementary Metal-Oxide Semiconductor) based sensors, used in consumer electronics, biometrics, traffic and security surveillance and PC imaging.
  • Motion Detectors: sensors which can be Infrared, Ultrasonic or Microwave/Radar technology. They are used in video games, security detection and light activation.

What is graphene?

Graphene is a two-dimensional material made of carbon atoms, often dubbed “miracle material” for its outstanding characteristics. It is 200 times stronger than steel at one atom thick, as well as the world’s most conductive material. It is so dense that the smallest atom of Helium cannot pass through it, but is also lightweight and transparent. Since its isolation in 2004, researchers and companies alike are fervently studying graphene, which is set to revolutionize various markets and produce improved processes, better performing components and new products.

Graphene and sensors

Graphene and sensors are a natural combination, as graphene’s large surface-to-volume ratio, unique optical properties, excellent electrical conductivity, high carrier mobility and density, high thermal conductivity and many other attributes can be greatly beneficial for sensor functions. The large surface area of graphene is able to enhance the surface loading of desired biomolecules, and excellent conductivity and small band gap can be beneficial for conducting electrons between biomolecules and the electrode surface.

Graphene-based chemical sensor photo

Graphene is thought to become especially widespread in biosensors and diagnostics. The large surface area of graphene can enhance the surface loading of desired biomolecules, and excellent conductivity and small band gap can be beneficial for conducting electrons between biomolecules and the electrode surface. Biosensors can be used, among other things, for the detection of a range of analytes like glucose, glutamate, cholesterol, hemoglobin and more. Graphene also has significant potential for enabling the development of electrochemical biosensors, based on direct electron transfer between the enzyme and the electrode surface.

Graphene will enable sensors that are smaller and lighter - providing endless design possibilities. They will also be more sensitive and able to detect smaller changes in matter, work more quickly and eventually even be less expensive than traditional sensors. Some graphene-based sensor designs contain a Field Effect Transistor (FET) with a graphene channel. Upon detection of the targeted analyte’s binding, the current through the transistor changes, which sends a signal that can be analyzed to determine several variables.

Graphene-based nanoelectronic devices have also been researched for use in DNA sensors (for detecting nucleobases and nucleotides), Gas sensors (for detection of different gases), PH sensors, environmental contamination sensors, strain and pressure sensors, and more.

Commercial activities in the field of graphene sensors

In June 2015, A collaboration between Bosch, the Germany-based engineering giant, and scientists at the Max-Planck Institute for Solid State Research yielded a graphene-based magnetic sensor 100 times more sensitive than an equivalent device based on silicon.

In August 2014, the US based Graphene Frontier announced raising $1.6m to expand the development and manufacturing of their graphene functionalized GFET sensors. Their “six sensors” brand for highly sensitive chemical and biological sensors can be used to diagnose diseases with sensitivity and efficiency unparalleled by traditional sensors.

Graphene Frontiers G-FET sensorG-FET Six-Sensors

In September 2014, the German AMO developed a graphene-based photodetector in collaboration with Alcatel Lucent Bell Labs, which is said to be the world’s fastest photodetector.

In November 2013, Nokia’s Cambridge research center developed a humidity sensor based on graphene oxide which is incredibly fast, thin, transparent, flexible and has great response and recovery times. Nokia also filed for a patent in August 2012 for a graphene-based photodetector that is transparent, thin and should ultimately be cheaper than traditional photodetectors.

Further reading

Latest Graphene Sensors news

UCF team enables graphene to better absorb light

Researchers at The University of Central Florida have come up with a finding that enables graphene to better absorb light and showed more than 45% absorption of light in a single layer of graphene. This may open the door to graphene-enhanced applications that require the incident light to be fully utilized, like next-generation light detectors, touchscreens, and more.

“This is the first published work on extremely high light absorption in graphene which is tunable dynamically,” the researchers said. “Theoretical studies show further design optimization can lead to further enhanced absorption close to 90%”.

University of Sussex team develops a graphene-based sensor with lifesaving potential

Researchers at the University of Sussex have developed a graphene-based sensor with the potential to prevent sudden infant death syndrome (SIDS) cases. The sensor is shaped like a flexible rubber tube filled with a solution of water, oil and particles graphene.

University of Sussex's graphene sensor for health monitoring image

the sensors were said to be the most sensitive liquid-based devices to have ever been developed. Utilizing graphene's conductivity, the solution inside the tube conducts electricity. When the tube is stretched by even a tiny amount, the conductivity also changes and this change can be detected, indicating that movement (such as the rising and falling of a breathing person's chest) is occurring.

Graphene Investment Guide

Manchester University team develops graphene sensors for IoT applications

Researchers at The University of Manchester have developed graphene sensors embedded into RFIDs, which may have the potential to revolutionize the Internet of Things (IoT). The team layered graphene-oxide over graphene to create a flexible heterostructures that function as humidity sensors for remote sensing with the ability to connect to any wireless network.

Manchester team devises graphene sensors for IoT applications image

The novel aspect of this development is that such sensors can be printed layer-by-layer for scalable mass production at very low costs. The device also requires no battery source as it harvests power from the receiver.

New low-cost graphene-based sensors for plants to enable new opportunities

Iowa State University researchers have created a new, low-cost, easily produced, graphene-based sensors-on-tape that can be attached to plants to provide data that was previously very hard to collect. This can help farmers to breed plants that are more efficient in using water, for example, but also open new possibilities for creating new sensors for biomedical diagnostics, for checking the structural integrity of buildings, monitoring the environment and, after appropriate modifications, for testing crops for diseases or pesticides.

''Tattoo'' sensors for plants image

The tiny graphene sensors that can be taped to plants, and the researchers have dubbed it a “plant tattoo sensor”. The plant sensors have been successfully tested in lab and pilot field experiments. The graphene-on-tape technology in this study has also been used to produce wearable strain and pressure sensors, including sensors built into a “smart glove” that measures hand movements.

Graphene-based cell-sized robots are on their way!

Researchers from Cornell have developed tiny graphene-enhanced robot exoskeletons that can rapidly change shape upon sensing chemical or thermal changes in its environment. And, they claim, these microscale machines – equipped with electronic, photonic and chemical payloads – could become a powerful platform for robotics at the size scale of biological microorganisms.

“We are trying to build what you might call an ‘exoskeleton’ for electronics,” said the team. “Right now, you can make little computer chips that do a lot of information-processing … but they don’t know how to move or cause something to bend”.

XFNANO: Graphene and graphene-like materials since 2009XFNANO: Graphene and graphene-like materials since 2009