Colorimetric sensing techniques require only the naked eye or ordinary visible color photography and are attractive because of their low cost, use of inexpensive equipment, and above all, their simple-to-understand results. Researchers have now developed a plasmonic colorimetric assay to detect mercuric ion based on urine. Compared to other gold-nanoparticle-based colorimetric systems, it showed excellent selectivity to mercury ions and good sensitivity as high as can be used for mercury ion detection in industrial wastewater.
Nanotechnology-enabled, paper-based sensors promise to be simple, portable, disposable, low power-consuming, and inexpensive sensor devices that will find ubiquitous use in medicine, detecting explosives, toxic substances, and environmental studies. Since monitoring needs for environmental, security, and medical purposes are growing fast, the demand for sensors that are low cost, low power-consuming, high sensitivity, and selective detection is increasing as well. Paper has been recognized as a particular class of supporting matrix for accommodating sensing materials. A team of Chinese researchers has now developed low-cost gas sensors by trapping single-walled carbon nanotubes in paper and demonstrated their effectiveness by testing it on ammonia.
Trace detection of explosives generally involves the collection of vapour or particulate samples and analyzing them using a sensitive sensor system. Various factors, such as wide variety of compounds that can be used as explosives, the vast number of deployment means and the lack of inexpensive sensors providing both high sensitivity and selectivity have made trace detection a very complex and costly task. High sensitivity and selectivity, along with the availability of low-cost sensors, is essential to combat explosives-based terrorism. Nanosensors have the potential to satisfy all the requirements for an effective platform for the trace detection of explosives.
Human breath contains a number of volatile organic components (VOCs). An accurate detection of a specific VOC - i.e., a biomarker for a particular disease - in the exhaled breath, can provide useful information for diagnosis of various diseases. The critical advantage of exhaled breath analysis is that it allows for non-invasive disease diagnosis. Researchers have now shown that that a chemiresistive sensor can work as a VOCs sensing device to detect very low concentrations of acetone if the sensing materials have optimized morphology and microstructure.
Conventional electronic tongues utilize pattern recognition for analysis using arrays of synthetic materials such as polymers, artificial membranes and semiconductors, for applications in the food and beverage industries. Even with current technological advances, e-tongue approaches still cannot mimic the biological features of the human tongue with regard to identifying elusive analytes in complex mixtures, such as food and beverage products. But researchers have now developed a human bitter-taste receptor as a nanobioelectronic tongue. They utilized a human taste receptor as a sensing element for mimicking the human taste system and selective detection.
Recent advances in materials, fabrication strategies and device designs for flexible and stretchable electronics and sensors make it possible to envision a not-too-distant future where ultra-thin, flexible circuits based on inorganic semiconductors can be wrapped and attached to any imaginable surface, including body parts and even internal organs. Robotic technologies will also benefit as it becomes possible to fabricate 'electronic skin' that, for instance, could allow surgical robots to interact, in a soft contacting mode, with their surroundings through touch. Researchers have now demonstrated that they can integrate high-quality silicon and other semiconductor devices on thin, stretchable sheets, to make systems that not only match the mechanics of the epidermis, but which take the full three dimensional shapes of the fingertip - and, by extension, other appendages or even internal organs, such as the heart.
Printed electronics has emerged as a key research field to meet the requirements of large area and cost-efficient production. The field of modern electronics is very general and includes not only printable interconnects, but also optoelectronics and magnetoelectronics. In this respect, cost-efficient versatile electronic building blocks, such as transistors, diodes and resistors, are already available as printed counterparts of conventional semiconductor elements. However, the element responding to a magnetic field, which is highly demanded for printable electronics, has not yet been realized and printable electronic sensors and contactless switches operating in combination with magnetic fields have not been reported so far. In new work, researchers in Germany have successfully overcome most of these issues. Researchers have now fabricated the first printable magnetic sensor that relies on the giant magnetoresistance (GMR) effect. The developed magneto-sensitive ink can be painted on any substrate - such as paper, polymers, ceramics, and glass - and retains a GMR ratio of up to 8% at ambient conditions. This value is beyond the state of the art.
It has been known for some time that graphene can be used for detection of individual gas molecules adsorbed on its surface - a graphene sensor can detect just a single molecule of a toxic gas. However, the extremely high sensitivity of graphene does not necessarily translate into its selectivity to various molecules. In other words, it can be detected that some molecules attached to the graphene surface change the resistivity of a graphene field-effect transistor but one cannot say what kind of a molecules have attached. Scientists have therefore thought that truly selective gas sensing with graphene devices requires the functionalization of graphene surface with some agents specific for different gas molecules. In new research, though, scientists have now found that chemical vapors change the noise spectra of graphene transistors. The noise signal for each gas is reproducible, opening the way for practical reliable and simple gas sensors made from graphene.