Olfaction, our sense of smell, depends on the capability of specialized sensory cells in the nose to detect airborne odorant molecules. These olfactory cells contain specific protein molecules that acts as 'olfactory receptors' - they bind only to specific odorant molecules present in the air inhaled through the nose. When such a binding event occurs, the olfactory receptors change their shape and this deformation triggers chemical and electrical signals which are eventually transmitted to the brain through neurons. So, in a nutshell, this is how we smell. Human and especially some animal noses (think bomb-sniffing dogs) are very sophisticated and extremely sensitive gas sensors that can distinguish between very similar gas molecules. Researchers have been trying for a while to replicate the human olfactory sense - a concept called electronic nose (e-nose). While most nanotechnology-based efforts have focused on nanowires, new research conducted in Korea has demonstrated the detection of specific odorant molecules with a single-carbon-atomic resolution using a human olfactory receptor-functionalized carbon nanotube based sensor.
Miniaturizing traditional laboratory assays to automated lab-on-a-chip devices holds tremendous potential for enabling multiplex, efficient, cost-effective and accurate pathogen sensing systems for both security and medical applications. These sensors could be used to detect bacteria such as E. coli and Salmonella, but also other pathogens that could be used for bioterrorism. Traditional identification methods required time intensive cell culturing processes but novel pathogen sensors based on nanomaterials are promising vastly improved and speedy detection technologies. A recent example is a label-free sensor chip assembled from peptide nanotubes that enables the electrical detection of viruses with an extremely low detection limit. This could lead to compact super-sensitive pathogen detection chips for point of care applications that have a high tolerance against false-positive signals.
Genomics and proteomics, the studies of genes and proteins, provide the underlying basis for many advances in drug development and effective treatments of diseases. These studies heavily rely on unveiling the behavior of a single DNA or protein in an investigative sample. You could compare this challenge to somehow finding, then catching and monitoring a particular fish in a vast ocean. The scientific term for 'catching the fish' is 'immobilization' - a powerful technique for the study of biochemical systems that allows for the continuous observation of dynamic behavior of a chosen target. Immobilization methods anchor the to be observed molecule onto a surface in order to restrict it from escaping the observation volume. Researchers have now developed a new platform which consists of a carbon nanotube nanoneedle for capturing, isolating and measuring the activity of miniscule amounts of proteins.
Artificial skin already exists that can detect pressure and recently, thanks to carbon nanotube rubber, it now even is stretchable. Then there is stretchable artificial skin that is used, for instance, to provide grafts for human burns victims, but it is insensitive to heat and pressure. Skin-like sensitivity, or the capability to recognize tactile information, will be an essential feature of future generations of robots. Of course you could also dream up some sci-fi scenarios where artificial electronic skin vastly enhances human perception and performance. The development of electronic skin requires high-performance tactile sensors that mimic human skin in terms of touch sensation over a large area, high flexibility, resolution, and sensitivity comparable to a human finger, as well as ease of signal extraction for speed and implementation. A recent review article summarizes the current state of developing artificial touch, an area where significant progress has been made over the past few years.
'Smart' is the key buzz word used by materials engineers when they describe the future of coatings, textiles, building structures, vehicles and just any material that you can think of. Materials are made 'smart' when they are engineered to have properties that change in a controlled manner under the influence of external stimuli such as mechanical stress, temperature, humidity, electric charge, magnetic fields etc. Smart materials have some form of sensor capability that detects a change in the material or its environment that then triggers some kind of action. Not only for use in smart materials but as general sensor materials, especially for monitoring large areas, the development of materials that act as 'chemical paints' - or coatings - by responding to a (bio)chemical parameter with a change in their optical properties has developed into an exciting new field. In a typical application, the object of interest is painted and the color or fluorescence of the paint is monitored by methods of optical imaging. This technique represents a simple but exciting new technology to monitor (bio)chemical and even physical parameters over relatively large areas and in real time without having to look at only a minute sample through a microscope.
Carbon nanomaterials have been extensively used in electroanalysis, and the most common forms are spherical fullerenes, cylindrical nanotubes, and carbon fibers and blacks. Since the discovery that individual carbon nanotubes (CNTs) can be used as nanoscale transistors, researchers have recognized their outstanding potential for electronic detection of biomolecules in solution, possibly down to single-molecule sensitivity. To detect biologically derived electronic signals, CNTs are often functionalized with linkers such as proteins and peptides to interface with soluble biologically relevant targets. Now, for the first time, scientists have tested nanometal decorated graphene (actually graphite nanoplatelets, a thickness of 10 nm would contain approximately 30 graphene sheets, considering an interlayer spacing of 0.335 nm) in biosensor application. As it turned out, this novel biosensor is among the best reported to date in both sensing performance and production cost.
Borrowing from nature's micro- and nanoscale propulsion systems, nanotechnology researchers have successfully used motor proteins to transport nanosized cargo in molecular sorting and nano-assembly devices. In so-called gliding assays, surface-attached motors propel cytoskeletal filaments, which in turn transport a cargo. However, cargo and motors both attach to the filament lattice and will affect each other. While an effect of cargo loading on transport speed has been described before, it has never been explained very well. To study this effect, scientists in Germany have observed single kinesin-1 molecules on streptavidin coated microtubules. They found that individual kinesin-1 motors frequently stopped upon encounters with attached streptavidin molecules. This work helps to understand the interactions of kinesin-1 and obstacles on the microtubule surface. An interesting, possibly even more important side result is that this understanding will not only help to optimize transport assays, balancing speed and cargo-loading, but can be used as a novel method for the detection of proteins as well.
Detecting the presence of a given substance at the molecular level, down to a single molecule, remains a considerable challenge for many nanotechnology sensor applications that range from nanobiotechnology research to environmental monitoring and antiterror or military applications. Currently, chemical functionalization techniques are used to specify what a nanoscale detector will sense. For biological molecules, this might mean developing an antibody/antigen pair, or an alternative synthetically generated ligand. For chemical gases, it is much more challenging to develop the right 'glue' that sticks a given gas to a substrate. The advantage of spectroscopic techniques such as Raman, infrared, and nuclear magnetic resonance spectroscopy is that they are label-free, i.e. they require no preconditioning in order to identify a given analyte. They are also highly selective, capable of distinguishing species that are chemically or functionally very similar. On the downside, spectroscopic methods face enormous challenges in measuring dilute concentrations of an analyte and generally involve the use of large, expensive equipment. This article describes a novel chemical detection technique called nanomechanical resonance spectroscopy.