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 from Michigan State University and Stanford University have invented the “NeuroString” — a graphene-based implantable probe that enables researchers to study the chemistry of brain and gut health.
“The mainstream way people are trying to understand the brain is to read and record electric signals,” said Jinxing Li, the paper’s first author and an assistant professor in MSU’s College of Engineering. “But chemical signals play just as significant a role in brain communication, and they are also directly related to diseases. My lab at MSU focuses on developing cutting-edge neuroprobes and microrobotics.”
Researchers at Zhejiang Universityת University of California, The Chinese University of Hong Kong, Peking University, Aalto University, University of Cambridge and Nanjing University have developed a new graphene-based photodetector that could detect light within a broader bandwidth. Their device could be used to develop new and more advanced imaging technologies.
The teams work is based on traditional charge-coupled device (CCD) and complementary metal-oxide-semiconductor (CMOS) imaging technologies. The researchers stated that their imaging devices, combining CCD's MOS photogate for high sensitivity and CMOS's independent pixel structure, can significantly benefit monolithic integration, performance, and readout.
Researchers at the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences (CAS), led by Prof. CHEN Tao, have designed strain-perception-strengthening (SPS) enabled biomimetic soft skin, which realizes the dynamic transformation from tactile to pain perception.
The synthetic skin is said to be elastic, conductive, and adaptive. It is composed of elastomeric thin-film and assembled graphene nanosheets with an interlocked structural interface.
Graphene-based intelligent quantum sensor can simultaneously detect the intensity, polarization and wavelength of light
A team of researchers from Yale University, The University of Texas at Dallas and the National Institute for Materials Science in Tsukuba, Japan, has built a graphene-based intelligent sensor that can simultaneously detect the intensity, polarization and wavelength of light, tapping into the quantum properties of electrons. The team estimates this breakthrough could help advance the fields of astronomy, health care, and remote sensing.
The researchers used twisted double bilayer graphene (TDBG)—that is, two atomic layers of natural stacked carbon atoms given a slight rotational twist—to build their sensing device. The twist reportedly reduces the crystal symmetry, and materials with atomic structures that are less symmetrical—in many cases—promise some intriguing physical properties that aren't found in those with greater symmetry.
SensFit Technologies partners with Footwork Podiatric Laboratory to develop graphene-enhanced smart orthotics
SensFit Technologies developed a smart shoe with inbuilt sensors, aiming to improve the quality of life of older people through the early detection of dementia, diabetic ulcers and other physical activity issues. Now, SensFit has announced that it is partnering with Footwork Podiatric Laboratory, a leading Australian custom-made orthotic manufacturer to develop Smart Orthotics to help diabetic ulcer treatment.
This product combines two innovative technologies: Sensfit’s unique graphene sensors integrated with AI and data analysis technology, combined with Footwork’s 3D printing technology to custom manufacture large volume orthotics.