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:
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.
ICFO researchers have recently demonstrated a new class of graphene-based flexible and transparent wearable devices that are conformable to the skin and can provide continuous and accurate measurements of multiple human vital signs.
These devices can measure heart rate, respiration rate and blood pulse oxygenation, as well as exposure to UV radiation from the sun. While the device measures the different parameters, the read-out is visualized and stored on a mobile phone interface connected to the wearable via Bluetooth. In addition, the device can operate battery-free since it is charged wirelessly through the phone.
Researchers from Chalmers University of Technology have demonstrated a graphene-based detector with the potential to revolutionize the sensors used in next-generation space telescopes. Beyond superconductors, there are few materials that can meet the requirements for making ultra-sensitive and fast terahertz (THz) detectors for astronomy. Chalmers researchers have shown that engineered graphene adds a new material paradigm for THz heterodyne detection.
"Graphene might be the only known material that remains an excellent conductor of electricity/heat even when having, effectively, no electrons. We have reached a near zero-electron scenario in graphene, also called Dirac point, by assembling electron-accepting molecules on its surface. Our results show that graphene is an exceptionally good material for THz heterodyne detection when doped to the Dirac point," says Samuel Lara-Avila, assistant professor at the Quantum Device Physics Laboratory and lead author of the paper.
Australia-based graphene and data analytics company, Imagine Intelligent Materials, has developed an integrated sensing solution that uses graphene coatings and edge-based signal processing devices to collect data from objects with large surface areas.
Proven over areas as large as 4,000 square meters, the system gathers data such as pressure, moisture, stress and temperature and is aimed at industrial and consumer applications in the IoT market.