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.
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.
The latest graphene sensor news:
A new experimental pilot line will integrate graphene and related layered materials (GRMs) in semiconductor platforms
The European Commission recently invited a group of Graphene Flagship partners and associated members to set up an experimental pilot line to integrate graphene and related layered materials (GRMs) in semiconductor platforms.
The project aims to establish a European ecosystem covering the entire value chain, from tool manufacturers and chemical and material providers to pilot lines. This collaborative project will pioneer the manufacture of new prototype electronics, photonics and sensors integrating GRMs. The 2D Experimental Pilot Line (2D-EPL) will offer prototyping services to companies, research centers and academics to develop their innovative technologies based on 2D materials in an established processing platform.
Sussex team granted £1 million funding to develop graphene-based applications like camouflage technology, smart tires and more
A University of Sussex research team, led by Professor Alan Dalton, has received new funding of £1 million from private company Advanced Material Development, to pursue their research into graphene and other nanomaterials.
The team will conduct research into various avenues, including camouflage technology to stop soldiers from being spotted by thermal imaging cameras or night vision goggles. The team will also develop their research into anti-counterfeiting graphene inks which can be printed onto clothes and medicine containers; incorporated into smart tires which monitor for problems; used on banknotes; included on metal-free radio-frequency identification tags (RFID) tags for supermarkets to track products; and wearable technology, including monitors for babies’ heartbeats or diabetic patients’ glucose levels.
Researchers at the University of Illinois at Urbana-Champaign have found that crumpling graphene makes it more than ten thousand times more sensitive to DNA by creating electrical "hot spots". This discovery could assist in addressing a known issue of graphene-based biosensors - the face that they require a lot of DNA in order to function properly.
"This sensor can detect ultra-low concentrations of molecules that are markers of disease, which is important for early diagnosis," said study leader Rashid Bashir, a professor of bioengineering and the dean of the Grainger College of Engineering at Illinois. "It's very sensitive, it's low-cost, it's easy to use, and it's using graphene in a new way."
As researchers and companies all over the world set out to battle the Coronavirus pandemic, many are revisiting graphene as a material with potential for helping to win this fight. The reasons for such potential could be found in graphene's known antibacterial/antiviral properties, its beneficial traits for medical sensors and devices and more.
Graphene has been shown in the past as extremely useful for creating various sensors. Earlier this month, a team led by Boston College researchers used a sheet of graphene to track the electronic signals inherent in biological structures, in order to develop a platform to selectively identify deadly strains of bacteria. In October 2019, Rice University team under chemist James Tour transformed their laser-induced graphene (LIG) into self-sterilizing filters that grab pathogens out of the air and kill them with small pulses of electricity. Commercially sold graphene-based sensors exist, like the graphene oxide (GO) sensor developed by the ICN2 Nanobioelectronics and Biosensors group that was added in 2016 to the list products offered by Biolin Scientific, a prestigious instrumentation company devoted to the production of analytical devices. The Q-Sense GO sensor enables interaction studies of GO with various analytes (measured substances) of interest and may open the door to various applications with interest for diagnostics, safety/security and environmental monitoring.
A team led by Boston College researchers has used a sheet of graphene to track the electronic signals inherent in biological structures, in order to develop a platform to selectively identify deadly strains of bacteria. This effort could lead to more accurate targeting of infections with appropriate antibiotics, according to the team.
The prototype demonstrates the first selective, rapid, and inexpensive electrical detection of the pathogenic bacterial species Staphylococcus aureus and antibiotic resistant Acinetobacter baumannii on a single platform, said Boston College Professor of Physics Kenneth Burch, a lead co-author of the paper.