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 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.
G-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
- Introduction to graphene
- Graphene company database
- How to invest in the graphene revolution
- The Graphene Handbook, our very own guide to the graphene market
- Graphene DNA Sequencing
Researchers design graphene-based infrared emitter for integrated photonic gas sensors
Researchers at AMO GmbH, KTH Royal Institute of Technology, Senseair AB and the University of Bundeswehr have developed a waveguide-integrated incandescent thermal mid-infrared emitter using graphene as the active material. This innovative approach is said to significantly enhance the efficiency, compactness, and reliability of gas sensor systems, paving the way for widespread applications across various industries.
Many applications require robust, real-time air quality monitoring solutions, driving the demand for distributed, networked, and compact gas sensors. Traditional gas sensing methods, including catalytic beads and semiconducting metal oxide sensors, suffer from performance degradation, frequent calibration needs, and limited sensor lifetimes due to their reliance on chemical reactions. Absorption spectroscopy offers a promising alternative by utilizing the fundamental absorption lines of several gases in the mid infrared (mid-IR) region, including greenhouse gases. This method provides high specificity, minimal drift, and long-term stability without chemically altering the sensor. The ability to “fingerprint” gases through characteristic absorption wavelengths, such as carbon dioxide (CO2) at 4.2 μm, makes it a promising technology for precise gas detection.
Researchers develop graphene-based battery-free lactic acid sensor
Scientists at the University of Bath, working in collaboration with Integrated Graphene, have created a new type of chemosensor (demonstrated for lactic acid sensing) which functions with electricity but without the need for reference electrodes or battery power. The new design potentially offers lower cost, better shelf-life, and ease of miniaturization compared to enzyme-based sensors. This could open up the possibility for an easy-to-use sensor to be used in remote locations, such as an athletics track, without the need for electricity-powered sensing equipment.
The sensor was able to detect lactic acid, a by-product generated by the body when it metabolizes carbohydrates or glucose for fuel, for example, during exercise. High levels of lactic acid are linked with higher risks of falling unconscious or into a coma and major organ failure.
Researchers propose "Universal Murray's Law" for synthetic materials
Researchers from the University of Cambridge, Tokyo Institute of Technology, University of Warwick and University of Namur have proposed a new materials theory based on "Murray's Law," applicable to a wide range of hierarchical structures, shapes and generalized transfer processes.
The scientists experimentally demonstrated optimal flow of various fluids in hierarchically planar and tubular graphene aerogel structures to validate the proposed law. By adjusting the macroscopic pores in such aerogel-based gas sensors, they also showed a significantly improved sensor response dynamics.
Tachmed partners with St George’s, University of London, to advance graphene-based health diagnostic platform
Tachmed, a UK-based developer of at-home digital healthcare solutions, has teamed up with experts in infection control at St George’s, University of London, to help accelerate the development of a new diagnostic platform for a range of health conditions, using graphene biosensor technology.
During the four-month collaboration, funded by an Innovate UK Accelerated Knowledge Transfer grant, Dr. Henry Staines, senior lecturer in global health at the Institute for Infection & Immunity at St George’s, will provide critical knowledge exchange. This is expected to boost development of the technology by optimizing Tachmed’s biosensor, which is required to confirm if a pathogen is present or not within a patient sample.
Graphene Trace secures £300k to tackle pressure ulcers
Graphene Trace, a UK-based startup that aims to use sensors to eradicate the problem of pressure ulcers, has been awarded a £300,000 grant by Innovate UK.
The startup believes its proprietary sensor technology for wheelchair users and hospital inpatients could reduce pressure ulcer onset by up to 95%. CEO Scott Dean said the grant will fund the creation of a prototype for its pressure ulcer prevention technology and bring it a step closer to going to market.
Researchers design a butterfly-inspired multisensory neuromorphic platform for integration of visual and chemical cues
It is a known fact that animals require the integration of cues collected from multiple sensory organs to enhance the overall perceptual experience and thereby facilitate better decision-making in most aspects of life. However, despite the importance of multisensory integration in animals, the field of artificial intelligence (AI) and neuromorphic computing has primarily focused on processing unisensory information. This lack of emphasis on multisensory integration can be attributed to the absence of a miniaturized hardware platform capable of co-locating multiple sensing modalities and enabling in-sensor and near-sensor processing.
a) A simplified abstraction of visual and chemical stimuli from male butterflies and visuo-chemical integration pathway in female butterflies. b) Butterfly-inspired neuromorphic hardware comprising of monolayer MoS2 memtransistor-based visual afferent neuron, graphene-based chemoreceptor neuron, and MoS2 memtransistor-based neuro-mimetic mating circuits. Image credit: Advanced Materials
In their recent study, researchers at Penn State University addressed this limitation by utilizing the chemo-sensing properties of graphene and the photo-sensing capability of monolayer molybdenum disulfide (MoS2) to create a multisensory platform for visuochemical integration.
Researchers create graphene-integrated bioelectronic mesh for tracking multimodal excitation-contraction dynamics in cardiac microtissues
Researchers at the University of Massachusetts and Massachusetts Institute of Technology (MIT) have successfully built a tissue-like bioelectronic mesh system integrated with an array of graphene sensors that can simultaneously measure both the electrical signal and the physical movement of cells in lab-grown human cardiac tissue.
A bioelectronic mesh, studded with graphene sensors (red), can measure the electrical signal and movement of cardiac tissue (purple and green) at the same time. Image credit: UMass Amherst
The tissue-like mesh can grow along with the cardiac cells, allowing researchers to observe how the heart’s mechanical and electrical functions change during the developmental process. The new device can be extremely useful for those studying cardiac disease as well as those studying the potentially toxic side-effects of many common drug therapies.
New project will focus on graphene 'lab on a chip' medical diagnostic technology for rapid detection of infections
Researchers at the Liverpool School of Tropical Medicine (LSTM) will collaborate with ProMake, a material science and diagnostic company, as part of Innovate UK's Accelerated Knowledge Transfer Scheme. The new project will investigate how graphene technology could be utilized to rapidly detect infection and act as the basis for new medical diagnostics.
ProMake has developed a novel device prototype, the 'BioPod', a hand-held point-of-care diagnostic containing the graphene lab-on-a-chip (LOC) electrode. The LOC uses functionalized graphene, a super-strong and thin material laced with specific receptors, to detect a wide range of pathogens. The aim is to use the BioPod in the same way as lateral flow tests (LFTs), to test for COVID-19 and other pathogens. However, unlike LFTs, which provide quick results but with less accuracy than tests processed in the lab, the BioPod's advanced technology has the potential to be more accurate and easier to interpret.
Researchers use graphene to develop a biosensor that accurately tests the freshness of meat
Researchers from the Vietnam Academy of Science and Technology, VNU University of Science, Hanoi University of Science and Technology and the Russian Academy of Sciences have developed a biosensor that uses graphene electrodes modified by zinc oxide nanoparticles to measure Hypoxanthine (HXA), a material that can be used as a marker for the freshness of meat. The team demonstrated the sensor’s efficacy on pork meat.
The freshness of animal meat in the food industry is an essential property determining its quality and safety. With advanced technology capable of preserving food for extended periods of time, meat can be shipped around the globe and so there is a vital need for effective testing of its condition. Despite the technological advances keeping meat fresh for as long as possible, certain aging processes are unavoidable. Adenosine triphosphate (ATP) is a molecule produced by breathing and responsible for providing energy to cells. When an animal stops breathing, ATP synthesis also stops, and the existing molecules decompose into acid, diminishing first flavor and then safety. Hypoxanthine (HXA) and xanthine are intermediate steps in this transition. Assessing their prevalence in meat indicates its freshness.
Researchers develop formaldehyde sensing at room temperature graphene aerogels
Researchers at the University of Cambridge and the University of Warwick have developed a fully 3D-printed quantum dot/graphene-based aerogel sensor for highly sensitive and real-time recognition of formaldehyde at room temperature. Formaldehyde is a known human carcinogen that is a common indoor air pollutant. However, its real-time and selective recognition from interfering gases has thus far remained challenging, especially for low-power sensors suffering from noise and baseline drift.
The new sensor uses artificial intelligence techniques to detect formaldehyde in real time at concentrations as low as eight parts per billion, far beyond the sensitivity of most indoor air quality sensors.