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

Graphene/cellulose nanofiber hybrid sensor to efficiently detect alcohol

Jul 14, 2017

An international group of researchers from Saudi Arabia, China and the US have developed a graphene-bacterial cellulose nanofiber (GC/BCN) hybrid sensor to detect alcohol (ethanol) with great efficiency. The sensor was described as flexible, transparent, highly sensitive and with an excellent alcohol recognition performance. Electrical tests in different liquid environments were performed, with remarkable results.

The researchers created a composite thin film composed of graphene and bacterial cellulose nanofibers. In this material, the bacterial cellulose nanofibres act as the host and the graphene as the filler material. Due to its excellent conductive properties, it was reported that graphene does not require the addition of a conductive filler material, unlike many composites. The Researchers constructed the composite using a combination of wet chemical, blending, sonication (Cole-Parmer), centrifugal (Centrifuge 5810, Eppendorf), dialysis and sputtering (Equipment Support Co) methods.

Researchers design a spray-on sensing technology that detects structural integrity

Jul 09, 2017

A team of researchers from Hong Kong Polytechnic University (PolyU) has developed sensors which can be sprayed directly onto flat or curved surfaces. The sensors, made from a hybrid of carbon black (CB), graphene, other conductive nano-scale particles, and polyvinylidene fluoride (PVDF), can be networked to extract rich real-time information on the health status of the structure being monitored.

The technology includes a sensor network with a number of the sprayed nanocomposite sensors and an ultrasound actuator to actively detect the health condition of the structure to which they are fixed. When the ultrasound actuator emits guided ultrasonic waves (GUWs), the sensors will receive and measure the waves. If damage is detected, such as a crack in the structure, propagation of GUWs will be interfered by the damage, leading to the wave scattering phenomena to be captured by the sensor network. The damage can then be characterised quantitatively and accurately.

Graphene Oxide market report

Researchers develop novel graphene-based phase modulator with high efficiency and minimized footprint

Jun 28, 2017

ICFO researchers, along with teams from CIC Nanogune, IIT and Columbia University, have developed a graphene-based phase modulator capable of tuning the light phase between 0 and 2π in situ.

Graphene-based phase modulator image

To this end, the researchers exploited the unique wavelength tunability of graphene plasmons, light coupled to electrons in graphene. In their work, they used ultra-high quality graphene to build a fully functional phase modulator with a device footprint of only 350 nm, which is 30 times than the wavelength of the infrared light used for this experiment.

Exeter team develops technique for improved graphene-based sensors

Jun 20, 2017

Exeter researchers have recently reported a new method to use graphene to produce photodetectors, which they feel could revolutionize the manufacturing of vital safety equipment, such as radiation and smoke detection units.

Exeter team's improved sensors image

The Exeter team has created a new type of photodector that is said to be able to sense light around 4500 times better than traditional graphene sensors. This could possibly be implemented to create sensoring and imaging equipment that is more stable in harsh conditions, as well as been smaller and most cost-effective. The team stated that “In this work we demonstrate that dressing the structure of graphene with molecules can transform the optical and electrical response of this wonder material and enable unprecedented applications”.

Zenyatta Ventures and Lakehead University announce scale-up of GO program

Jun 16, 2017

Zenyatta Ventures has announced a program for a scaled-up production method of its graphite to graphene oxide for applications like water treatment, sensors, supercapacitors and Li‐ion batteries. The program is receiving grant funding from the Ontario Centres for Excellence (OCE) to allow a team of scientists at Lakehead University in Ontario, Canada to carry out this research.

The OCE funding helps established Ontario‐based companies develop, implement and commercialize technical innovations by supporting partnerships with publicly‐funded post‐secondary institutions. The focus of the research work will be on scaling up production methods for Zenyatta’s graphite to GO, a first critical step towards commercialization of the technology. The OCE VIP II $100,000 grant will be administered over two years and Zenyatta will be contributing $50,000 in cash and $60,000 in‐kind support to the project.

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