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

CVD Graphene prices continue to drop as commercial applications start to enter the market

Nov 13, 2017

CVD processes are used to create high-quality single layer (also bi-layer and tri-layer) graphene sheets. These kinds of sheets exhibit exceptional properties and can be used in a variety of exciting applications, from touch layers to transistors and sensors. For many years, CVD has been a high cost production process and this graphene is still mostly used in research projects in academic and research institutes, but prices are gradually dropping, to the point where commercial applications are starting to appear on the market.

Graphenea Monolayer CVD prices (2015-2017)

Recent years have, as we said, brought on a continuing price drop in CVD graphene prices. Spain-based Graphenea, a global CVD graphene leader, has an online shop in which it offers its high-end CVD graphene samples. We have been tracking the prices of Graphenea's CVD graphene since late 2015, and the graph above shows the price decrease.

Researchers at The University of Manchester create miniaturized pressure sensors using graphene membranes

Nov 12, 2017

Researchers at The University of Manchester have fabricated highly sensitive miniaturized pressure sensors using graphene membranes.

The team reported that the new sensor was made possible by developing a way to effectively float a graphene membrane mere nanometers above a silicon chip. When pressure moves this membrane closer to the surface of the chip, the resulting change in capacitance is measured to read out the pressure change. By fabricating thousands of such floating membranes next to each other, a device can be made of exceptionally high sensitivity to pressure changes.

Graphene Supercapacitors Market Report

New graphene-based sensor provides real-time detection of contaminants in water

Nov 05, 2017

Researchers at the University of Wisconsin-Milwaukee will be presenting a graphene-based sensing platform for real-time, low-cost detection of various water contaminants at the AVS's 64th International Symposium & Exhibition, being held Oct. 29-Nov. 3, 2017, in Tampa, Florida. The new sensor detects heavy metals, bacteria, nitrates and phosphates.

The sensor works by placing graphene-based nanosheets that are semiconducting between an electrode gap. The electrical conductivity of the graphene material changes with the binding of substances, called analytes, to its surface and their chemical constituents are identified and measured. "The magnitude of the conductivity change can be correlated to the concentration of analyte, and the technology also involves the functionalization of the graphene material surface with specific probes that can target a specific analyte," said the researchers.

A graphene-based flexible terahertz detector developed by Chalmers team

Oct 31, 2017

Researchers at Chalmers University have developed a flexible detector for terahertz frequencies (1000 gigahertz) using graphene transistors on plastic substrates. It is said to be the first of its kind, and can extend the use of terahertz technology to applications that require flexible electronics, like wireless sensor networks and wearable technology.

A graphene-based flexible terahertz detector has been developed by researchers at Chalmers image

At room temperature, the translucent and flexible device detects signals in the frequency range 330 to 500 gigahertz. The technique can be used for imaging in the terahertz area (THz camera), but also for identifying different substances (sensor). It may also be of potential benefit in health care, where terahertz waves can be used to detect cancer. Other areas where the detector could be used are imaging sensors for vehicles or for wireless communications.

Inkjet-printed graphene-based strain sensor shows promise

Oct 29, 2017

Researchers in the UK (the University of Manchester) and Italy (the University of Pisa) have developed an inkjet-printed graphene strain gauge sensor on paper. The device is said to have a gauge factor of up to 125 even when very small strains are applied, and its overall sensitivity and performance can be tuned by different printing parameters, such as drop-spacing and number of printing passes. It might be used in applications like robot skin and health monitoring applications, and in smart packaging.

Inkjet-printed graphene-based water quality sensors image

The team made their strain gauge by depositing conductive lines made from a network of graphene flakes (dispersed in water as the solvent) on a PEL P60 paper substrate using a simple Dimatix DMP-2850 inkjet printer. This printer can create and define patterns over an area of about 200 mm x 300 mm and handle substrates that are up to 25 mm thick. A waveform editor and a drop-watch camera system were used to manipulate electronic pulses to the jetting deice for optimizing the drops’ characteristics as they were ejected from the nozzle.

PlanarTECH - The 2D Materials Solution ProviderPlanarTECH - The 2D Materials Solution Provider