The Kynix Blog - Sensor

It takes a very, very clean room to build a detector sensitive enough to see the light from the beginning of the universe.Work is underway at the U.S. Department of Energy's (DOE's) Argonne National Laboratory on a new "clean room." The new lab will be specially suited for building parts for ultra-sensitive detectors—such as those to carry out improved X-ray research, or for the South Pole Telescope to search for light from the early days of the universe."This will be a unique facility, and a wonderful investment for the future of the laboratory," said Supratik Guha, who heads the Center for Nanoscale Materials, a DOE Office of Science User Facility adjacent to where the new space will be located.Clean rooms are a special kind of laboratory that is heavily filtered and cleaned, so that no free-floating particles interfere with delicate work. Take a cube of air one foot on a side: In a normal room in your house or office, this cube contains about one million free-floating particles of dust, dirt and other materials. In the clean room, it's no more than 100.This environment is what you need to build detectors that can detect the tiniest amount of energy striking the surface."Even a few stray specks of dust in the niobium can throw off the design for these detectors," said Marcel Demarteau, who heads the High Energy Physics Division at Argonne and will be a key user of the new lab.One use for such detectors is in the South Pole Telescope in Antarctica, one of several telescopes searching for light waves that have traveled throughout the universe since the moments after the Big Bang. This kind of light is called the Cosmic Microwave Background radiation.Because the light has traveled across space for the 13.8 billion years since the universe began, it has encountered all sorts of obstacles that slightly change its power spectrum—galaxy clusters, patches of dark matter, even our own atmosphere. "We have to correct for these to map the Cosmic Microwave Background signature we're looking for, but these small perturbations themselves hold an enormous amount of very valuable information about the composition of the universe," Demarteau said.  The most sensitive instruments today to find such signals are detectors made from superconductors. Superconductors are extremely sensitive materials that change properties dramatically when their temperature is raised even a tiny bit, and scientists can build components that react to specific frequencies to detect the signature of the Cosmic Microwave Background. The new clean room should allow researchers to build even more sensitive detectors—think of a camera that takes 150-pixel pictures versus one that can take 500,000-pixel images.The same technology will also offer researchers a chance to get better close-ups of the atomic makeup of objects being studied at the Advanced Photon Source, a DOE Office of Science User Facility at Argonne where scientists use X-rays to study everything from car fuel injectors to proteins that play roles in disease.The Advanced Photon Source sends beams of high-energy X-rays at a sample of whatever scientists are studying: a new solar cell material, a sample of volcanic glass from Greenland, a protein involved in photosynthesis. The X-rays hit the sample and scatter off in all directions. Very sensitive detectors pick up that scatter and reveal the chemical and atomic layout of the sample. The better the detector, the more information you can get; so Advanced Photon Source scientists are always looking for new ways to improve those detectors."The type of detector we want to build, nobody makes commercially: so we have to build our own," said Thomas Cecil, an engineer with the Advanced Photon Source. The new clean room will allow them to experiment with new kinds of transition edge sensors, which he said they hope could eventually improve the sensitivity by one or even two orders of magnitude compared to traditional silicon-based detectors.Building such technology is an excruciatingly delicate process, in which they lay down multiple coatings just a few nanometers thick—less than a hundredth of the diameter of a human hair—of superconducting materials and etch patterns into them. Then they repeat the process all over again, for up to 15 layers.The detector itself is so precise that it's operated at temperatures colder than outer space to achieve maximum sensitivity. "It's an excellent opportunity for us to push the boundaries of what's possible," Cecil said.Other potential uses, Demarteau said, include quantum computing as well as homeland security: building detectors that can pick out the particular signature of a specific kind of radiation, to detect if terrorists are carrying a dirty bomb made out of, for example, cesium-137. 

A group of researchers at Osaka University, succeeded in producing nanostructured gas sensor devices for detecting volatile organic compounds (VOC) in breath for the purpose of healthcare in time equivalent to or shorter than one tenth of the time required for manufacturing conventional gas sensors. This group improved conventional complicated production methods, developing a simple production method of just sintering substrates applied with materials. This gas sensor's sensing response was comparable to the top-of-the-line sensors reported all over the world.Research leading detection of low concentrations of gas present in exhaled human breath to health checkups and early detection and treatment of serious diseases is being performed. As gas sensors using nanomaterials can detect various gases even at low concentrations, installing such sensors in electronic healthcare devices is sought after, and research and development are being actively conducted.Semiconductor gas sensors detect gas through reduced electrical resistance due to gas molecules attached to the surface of crystalline semiconductor materials. For this, gas sensors need a specific surface area of nanomaterials. In order to use nanomaterials for conventional gas sensors, a complicated flow was necessary, from nanomaterials synthesis to cleansing, uniform dispersion of solvent, applying on substrates, and sintering. Thus, there is a concern that manufacturing technology of such gas sensors requires significant time and labor, increasing cost.A group of researchers led by Assistant Professor Tohru Sugahara (SUGANUMA Lab.) at The Institute of Scientific and Industrial Research, Osaka University, succeeded in producing nanostructured gas sensor devices for detecting volatile organic compounds (VOC) in breath for the purpose of healthcare in time equivalent to or shorter than one tenth of the time required for manufacturing conventional gas sensors. This group improved conventional complicated production methods, developing a simple production method of just sintering substrates applied with materials. This gas sensor's sensing response was comparable to the top-of-the-line sensors reported all over the world.Since demand in healthcare products is on the rise, there is a lot of activity in research and development of sensors for checking health and disease by examining the gas components of a person's breath. Breathalyzers for finding out who is driving drunk have already been commercialized. Recently, breath sensors for early detection of life-style diseases such as cancer and diabetes have been developed, but most of them are large, bulky and expensive. If gas sensors with high sensitivity are produced thanks to this group's research results, portable breath sensors enabling early detection of diseases will gain popularity.Reference:KGZ10 KGZ10-SPGMS10RVS  

Healthcare practitioners may one day be able to physically screen for breast cancer using pressure-sensitive rubber gloves to detect tumors, owing to a transparent, bendable and sensitive pressure sensor newly developed by Japanese and American teams.Conventional pressure sensors are flexible enough to fit to soft surfaces such as human skin, but they cannot measure pressure changes accurately once they are twisted or wrinkled, making them unsuitable for use on complex and moving surfaces. Additionally, it is difficult to reduce them below 100 micrometers thickness because of limitations in current production methods.To address these issues, an international team of researchers led by Dr. Sungwon Lee and Professor Takao Someya of the University of Tokyo's Graduate School of Engineering has developed a nanofiber-type pressure sensor that can measure pressure distribution of rounded surfaces such as an inflated balloon and maintain its sensing accuracy even when bent over a radius of 80 micrometers, equivalent to just twice the width of a human hair. The sensor is roughly 8 micrometers thick and can measure the pressure in 144 locations at once.The device demonstrated in this study consists of organic transistors, electronic switches made from carbon and oxygen based organic materials, and a pressure sensitive nanofiber structure. Carbon nanotubes and graphene were added to an elastic polymer to create nanofibers with a diameter of 300 to 700 nanometers, which were then entangled with each other to form a transparent, thin and light porous structure."We've also tested the performance of our pressure sensor with an artificial blood vessel and found that it could detect small pressure changes and speed of pressure propagation," says Lee. He continues, "Flexible electronics have great potential for implantable and wearable devices. I realized that many groups are developing flexible sensors that can measure pressure but none of them are suitable for measuring real objects since they are sensitive to distortion. That was my main motivation and I think we have proposed an effective solution to this problem."Reference:13C5000PA4K19C050PA4KMLH100PGM01B  

As we push the limits of agriculture to feed more people in a warmer world, we do not understand how plants sense temperature.In a surprising turn of events scientists have just learned that plant light sensors also respond to temperature.Plants contain specialized light-sensitive proteins that change shape when they absorb light, much as do the photopigments in the human eye. All plants have three main red-light photoreceptors, called phytochrome A, B and C.As part of an effort to create plants that can tolerate different growth conditions, Richard Vierstra the George and Charmaine Mallinckrodt Professor in Arts & Sciences at Washington University in St. Louis has been developing a library of phytochrome B mutants, including ones that are much more or less sensitive to light than the wild type plant.To better understand their mutant plants, the Vierstra lab shared them with Jorge J. Casal lab in Argentina where doctoral student Martina Legris grew them under a wide variety of carefully controlled conditions."We got 'weird' results that couldn't be explained unless the phytochrome we were working with was sensitive to temperature as well as light," Vierstra said.As the temperature rose, some plants exposed to constant sunlight generate less of the biologically active form of phytochrome B—not more, as you'd expect.At summer temperatures, these plants behave as though they're in dim light even though they're in bright sun.The findings will be published in the Oct. 27 issue of Science, together with a companion paper also on plant temperature sensors by a lab at the University of Cambridge in England.A switch with the jittersVierstra explains that phytochrome proteins work by switching between two forms, called Pr and Pfr.The Pr form is best at absorbing red light, which is plentiful in full sun. When it absorbs red light, phytochrome converts to the Pfr state, which is better at absorbing far-red light that dominates in shade. When the Pfr absorbs far-red light, it switches back to the Pr form.This clever little system is able to detect many different qualities of light, including the light intensity (encoded in the speed at which the molecule bounces from one form to another), and the color of the light (encoded by the ratio of the Pfr form to the Pr form). Intensity tells a seed when to emerge from the soil and color tells the seeding when to grow tall to avoid shade."The beauty of this is you can purify the phytochromes, put them in a test tube and watch them switch forms simply by shining red or far-red light on the solutions," Vierstra said. "So they're not figments of our imagination."An hour glass that runs too fastBut this description leaves out one conversion. Pfr can convert to Pr by absorbing far-red light but also by a process called thermal reversion, which occurs without light.People thought thermal reversion worked like an hour glass, Vierstra said. As soon as the sun set, the hour glass started running, and Pfr started trickling back to the Pr form. The amount of Pfr at the end of the night then told the plant how long the night was.This is important because the length of night varies with the season, especially away from the Equator. So changes in day (and night) length helps plants to tell where they are in the seasonal cycle, which in turn helps them to flower in the right season.Nobody had been able to test the idea that thermal reversion was an hourglass, or timer, however. But as they were tinkering with phytochrome B, the Vierstra lab made phytochrome mutants that were fast reverters and ones that were slow reverters. And these mutants were among those that traveled to Argentina.When they grew the plants, the Casals lab got strange results they could understand only if thermal reversion is much faster than anyone realized; and only if the rate of reversion is very sensitive to temperature. In other words, the only possible interpretationwas that phytochrome B in the wild type (unmodified) plant is a temperature as well as light sensor."The plant is looking for Pfr, which tells it the light is on," said Vierstra. "In sunlight a plant slowly makes more and more Pfr until the reaction that converts Pr to Pfr saturates. But as the temperature rises, the thermal reversion starts running so fast, the plants accumulate relatively little Pfr."You would expect that at higher temperatures the Pr -> Pfr reaction would go faster," Vierstra said, "and it probably does, but thermal reversion goes even faster. It erases the light signal because the reversion reaction is more sensitive to temperature than the one creating the light signal."You can predict what this will do as temperature rises," Vierstra said. "Plants that make lots of Pfr are short, intensely green and happy. But thermal reversion will draw down the Pfr at higher temperatures, so that plants will respond as if they are in the dark (even though they are in the light) and grow tall and leggy.""We don't yet know right now whether it's just phytochrome B that's a temperature sensor," Vierstra said. So right now members of his team, including Research Scientist Sethe Burgie, are trying to get accurate measurement on the other phytochromes. "Once we have this figured out, we could make mutants that are less or more sensitive to temperature by modifying thermal reversion."Coming in from the cold"Phytochromes are the worst to work on," Vierstra said. "You have to spend four days in the dark to purify them. They are incredibly unstable, they are present at very low levels, and they have got all kinds of variants. And unlike most other proteins, their amino-acid sequences also don't tell us how phytochromes work."So when people purify phytochromes, they want to keep the proteins as happy as possible and that means keeping them as cold as possible. All the experiments are done on ice!"And that's why we didn't realize until now that phytochromes could act as temperature sensors!"Reference:LM50BIM3/NOPBLM61CIM3XTMP03FT9Z  

Train delays due to leaves on the line could be a thing of the past if a prototype developed at the University of Birmingham is adopted by railway networks.Every year, thousands of commuters endure the frustration of Autumn delays caused by the accumulation of leafy slush on train tracks – and these problems usually reach their peak in mid-November, when leaf loss is coupled with high levels of moisture in the air or on the ground.Lee Chapman, Professor of Climate Resilience from the University, was inspired by the Internet of Things, which uses a range of innovative power, communication and sensing technology to aggregate real-time, on the ground, data.Funded by EPSRC and the Rail Safety and Standards Board, he worked with Alta Innovations, the University of Birmingham's technology transfer company, to transform the concept into a reality. His new technology, called AutumnSense, uses low-cost sensors to continuously measure the level of moisture on the railway line at potentially thousands of sites across the network. By linking this data with a leaf-fall forecast, operators can identify where and when the risk is greatest. This allows the precise and efficient use of automated treatment trains, which can clear the lines before the morning rush hour starts. His team are now testing the next element of the solution which is a low-cost method to count the number of leaves remaining on the trees.Professor Chapman's team had previously developed low-cost devices that are fitted to lamp-posts, and transmit data on road surface temperatures, to show precisely where road gritting is needed, and where it isn't. The road technology, called WinterSense, is currently being tested by commercial partners and is expected to be in mass production by the end of this winter.Professor Chapman said, "One of the major issues with road and rail safety is that hazardous conditions are usually highly localised. For remedial actions to be efficient, and demonstrate 'best value' for the taxpayer, resources should be deployed where they are needed, rather than in a blanket fashion."He is marketing AutumnSense and WinterSense through AltaSense, an operating division of Alta Innovations, and hopes to incorporate by Autumn 2017.He said, "Even though leaf loss and damp conditions can largely be predicted - and despite automated treatment trains working round the clock from October to December - a windy, rainy night still causes havoc for commuters. We have run an initial trial of AutumnSense on a stretch of London Underground tracks that are above ground, and are hoping to move quickly towards a fuller network wide trial."Wet leaves pose a very real safety challenge for train operators, potentially doubling the breaking distance and causing signalling issues, or 'disappearing trains' on the rail control systems due to the electrically insulating effect of the leaves which can prevent operation of track circuits. Leaves on the line are only an issue when they are mixed with moisture or dew, creating a slippery, Teflon-like substance. Reference:KY45-D7E-1KY45-BU-27135-000KY45-1005447-1 

An ultra-compact implantable image sensor using body channel communication has been demonstrated in Japan. The body channel approach allows the sensor-transmitter device to be much smaller and use less power than an RF wireless unit.  Fundamental limitsInterest in implantable medical sensors is on the rise as developments in established technologies and new concepts are making more and more applications feasible. One thing that all such sensors share is the need to be able to get the information they gather within the body, out of the body.RF communication is widely used for such applications, however, with implantable devices size reduction is generally desirable to reduce invasiveness, and in some applications there are also specific size limitations, owing to where and how the sensors are to be implanted. For example, sensors intended for use inside the brain need to be very compact.Using smaller antennas generally means using higher frequencies, and that in turn leads to attenuation problems with biological tissues. To compensate for increased attenuation more power is needed, which is also a serious issue for an implantable device.Conductive communicationAn alternative wireless approach to sending the data is body channel communication, in which an electrical signal is transmitted by conduction through the tissues of the body. In this issue of Electronics Letters, researchers from the Nara Institute of Science and Technology's Graduate School of Materials Science report using this approach to transmit and receive image data from a CMOS sensor fully implanted in a simulated body environment.Their sensor design, using body channel as the transmission method, will allow data to be read from the device by attaching an electrode to the surface of the body near the implantation site, as well as allowing the sensor unit itself to be low-power and small."Our implantable CMOS image sensor is intended for biomedical applications such as brain functional imaging," explains team member Hajime Hayami. "It can be planted with minimum invasiveness. Its features enable implantation of a number of sensors in a brain to investigate collaborative neural activities."In their experiments, the team at Nara have transmitted images from a CMOS sensor submerged in phosphate buffer saline (PBS), a body simulant material, to a receiver electrode 2 mm away. The experiments prove the principle of operation for this form of communication and even this small distance is enough to allow in vivo use in smaller animals."We are planning to apply our device to brain functional imaging of a mouse brain in the near future. Because the size of a mouse brain is only a few mm thick, the transmission distance of 2 mm is sufficient. Even in the case of signal transmission through a longer distance with a larger animal, the experimental results indicate that this method can be applied by adjusting the sensitivity of the receiver circuit," said Hayami.Neural arraysBefore the team can proceed with implantation in an animal, they need to integrate all of their PCB based devices into a single chip. This chip has already been designed and they are now working on the fabrication, with the goal of beginning implantation experiments by the end of 2014.Meanwhile, the Nara researchers have also been working to develop the design and say that relatively long distance transmission is now possible through improvements to the receiver circuit. On the sensor/transmitter side, they have also shown that they can use pulse-width modulation rather than an ADC output from the image sensor.The central goal of their work is creating tools for research into the human brain. "Our research group aims to elucidate the cooperative neural activity with distributed ultra-small sensors in the brain. We think we can achieve the goal by designing more intelligent chips based on the proposed communication method," said Hayami.The team believe that current sociological trends, including aging societies, will continue to drive demand for implantable devices, and that the applications of this kind of technology may develop to include more natural interaction between users and technology. Hayami commented that "I hope we will create an epoch where one can unconsciously use implantable devices by developing a brain-machine interface."Reference:KY45-OVM7695-RAEAKY45- OV09726-A40A-1DKY45- MT9P001I12STC