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:
Haydale has announced that it has signed a supply agreement to provide 76kg of its propriety piezoresistive ink to HP1 Technologies (HP1T) over an 18-month period. The value of the Supply Agreement was not disclosed.
HP1T creates bespoke flexible, printed, functionalized nano carbon-based sensor systems that can measure and collect high quality impact and pressure data. This newly signed supply agreement will see Haydale become HP1T's single supplier of functionalized nano carbon inks.
Finland-based Emberion recently announced its plan to present new products for visible light to shortwave infrared (VIS-SWIR) detection at SPIE Photonics West in San Francisco 5-7.2.2019. The showcased linear array is said to have been specifically designed for spectroscopy and use graphene as a charge transducing layer.
Emberion introduces a cost-competitive 512 × 1 pixel VIS-SWIR linear array sensor for visible to shortwave infrared spectral range. The sensor provides superior and consistent responsivity with very low noise over the broad (400 – 1800 nm) spectral range. The sensor comprises an array of 25 × 500 µm2 pixels monolithically built on a tailor-made CMOS readout integrated circuit. The ROIC contains an analog front-end, performs analog-to-digital conversion and signal pre-processing, implements an electric shutter, and provides digital data output with up to 16 bits resolution.
Graphene-based implant that records brain activity at low frequencies may change our understanding of the brain
Researchers from ICN2, IMB-CNM, CSIC, IDIBAPS, and ICFO have designed a graphene-based implant able to record electrical activity in the brain at extremely low frequencies and over large areas.
The team explains that electrode arrays currently used to record the brain’s electrical activity are only able to detect activity over a certain frequency threshold. The new graphene-based technology presented in this work overcomes this technical limitation, allowing access to information found below 0.1 Hz, while at the same time paving the way for future brain-computer interfaces.
Garmor, manufacturer of low-cost graphene oxide, rGO and developer of innovative GO production methods, recently developed a graphene-enhanced polymeric coating with a 390% reported improvement in tensile strength. Garmor stated that it is already marketing this technology as it has already been fielded and used in commercial applications. Here's a video showing side-by-side testing of the original polymer (left) and the graphene-enhanced polymer (right) shown at 4X normal speed.
In addition, Garmor announced the development of an innovative process for converting insulating polymeric fibers into electrically conductive fibers with minimal cost and no waste products. The method has resulted in composites with single-digit graphene loadings delivering conductivity as high as .023 S/cm. Garmor sees such performance as ideal for wearable sensors and other applications that require integrated approaches to solving weight and measurement issues.
A team of researchers from Russia, UK, Japan and Italy has created a graphene-based terahertz detector.
The team explains that the reason for the inefficiency of existing terahertz detectors is the mismatch between the size of the detecting element, the transistor—about one-millionth of a meter—and the typical wavelength of terahertz radiation, which is about 100 times greater. This results in the wave passing the detector by without any interaction.