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:
Scientists at the University of Oregon have designed a new method of measuring light—with the help of microscopic drums to hear light. The technology, known as a “graphene nanomechanical bolometer,” detects almost every color of light at high temperatures and high speeds.
“This tool is the fastest and most sensitive in its class,” said Benjamín Alemán, a professor of physics and a member of the University of Oregon’s Center for Optical, Molecular, and Quantum Science and an associate of the Phil and Penny Knight Campus for Accelerating Scientific Impact.
A research team led by Graphene Flagship partners Consiglio Nazionale delle Ricerche (CNR), Italy, and Chalmers University of Technology, Sweden, together with a team at the University of Modena, Italy, has created a new qualitative graphene-based sensor for morphine, that could be used by police to detect opiate abuse using suspects' urine samples.
Morphine is the main metabolite of heroin. The new sensor provides a fast-acting 'rough test' that yields a positive response if morphine concentration in urine exceeds a certain threshold. The sensor could be used by police forces during criminal investigations and roadside stops, in a similar way to how breathalyzers are used to test alcohol levels in suspected drunk drivers.
Tetra Pak has joined the Graphene Flagship project as the exclusive representative from the packaging industry to explore possible future applications of graphene in food and beverage manufacturing.
As part of the programme, packaging material innovations are being examined to see how graphene could offer coatings to reduce carbon footprint in the packaging supply chain.
Stevens Institute of Technology (SIT), a private, coeducational research university located in New Jersey, United States, has signed an exclusive licensing agreement with Bonbouton for the right to use and further develop a graphene sensing system that detects early signs of foot ulcers before they form so people living with diabetes can access preventative healthcare and confidently manage their health.
The smart insole can be inserted into a sneaker or dress shoe to passively monitor the foot health of a person living with diabetes. The data are then sent to a companion app which can be accessed by the patient and shared with their healthcare provider, who can determine if intervention or treatment is needed.
BioMed X has announced the completion of its first research collaboration project with Roche Diagnostics in the field of nanomaterial-based biosensors for near patient testing. BioMed X successfully achieved the proof of principle for a new sensor platform allowing the analysis of several different parameters from blood samples with one single device.
The project was initiated in 2015 as a call for application using BioMed X’s proprietary crowdsourcing platform for project proposals. As a result of an international innovation challenge, a team of early-career researchers from five different countries worked in Germany on the design of a field effect transistor-based multimodal sensing platform for proteins, blood gases and electrolytes, metabolites and enzymes with a single-use disposable material for point-of-care diagnostics.