It has proven difficult to directly manufacture functional nanostructures and nanodevices with predetermined designs using bottom-up processes alone. So far, developing top-down machining techniques capable of fabricating structural/functional nanostructures and nanodevices appears to be indispensable, but mechanical machining tools with nanometer precision are still lacking. A grand challenge in nanotechnology is to machine three-dimensional nanostructures in a controllable and reproducible fashion. That begs the question if traditional top-down mechanical machining can also be realized at the nanoscale. So far, the conventional wisdom has been that traditional top-down mechanical machining like cutting and milling using a lathe is impossible at the nanoscale. Nanotechnologists considered most of the traditional top-down approaches as not applicable for fabricating nanostructure and nanodevices. However, as it turns out, there still is room at the bottom for traditional mechanical machining.
Freshwater could become the oil of the 21st century - scarce, expensive and fought over. While over 70 per cent of the Earth's surface is covered by water, most of it is unusable for human consumption. Technological advances have made desalination and demineralization feasible - albeit expensive - solutions for increasing the world's supply of freshwater. However, nanotechnology- based water purification devices have the potential to transform the field of desalination. Researchers have now demonstrated a new, efficient and fouling-free desalination process based on the ion concentration polarization (ICP) phenomenon - a fundamental electrochemical transport phenomenon that occurs when an ion current is passed through ion-selective membranes - for direct desalination of sea water.
Surface energy is ubiquitous in nature and it plays an important role in many scientific areas such as for instance surface physics, biophysics, surface chemistry, or catalysis. So far it has been impractical to consider utilizing surface energy as an energy source because there are few molecules or atoms involved in the surface interaction and the density of surface energy is low. However, due to the lower power consumption requirements of nanotechnology devices and the higher specific surface area for nanomaterials it appears attractive to use surface energy at the nanoscale. Researchers in China have now demonstrated that an effective design of single-walled carbon nanotubes can be used to convert the surface energy of liquids into electricity.
Numerous research groups around the world are inspired by the biomineralization processes found in nature - the process by which living organisms produce inorganic materials (minerals) found in bones, teeth, or shells. In this process, the formation of the mineral is controlled with great precision by specialized organic biomolecules such as sugars and proteins. Whereas the fabrication of many man-made crystals requires elevated temperatures and strong chemical solutions, nature's organisms have long been able to lay down elaborate mineral structures at ambient temperatures. Being able to duplicate nature's 'production process' would potentially allow for much simpler and 'greener' fabrication technologies than the ones employed today. To that end, researchers have developed a new nanofabrication methodology to generate crystalline oxide semiconductor nanopatterns under mild conditions.
In contrast with microchannel-based fluidics, the manipulation of discrete droplets without using microfluidic channels is a new field. Here, a liquid droplet is not confined to a closed channel and there is no risk of being adsorbed on a channel wall. A liquid marble, a liquid encapsulated by non-wetting powder, could be a new microfluidic device, which is especially useful for handling single liquid droplet. One of the challenges for using liquid marbles as microfluidic devices is the communication between the liquid droplet and the external devices/materials. Researchers in Australia have been trying to develop 'field-responsive smart liquid marbles' which can be opened and closed reversibly on demand, such that the liquid in the marble can be easily taken and other liquid can also be added into the marble easily. The mechanically robust magnetic liquid marble, prepared by coating a water droplet with highly hydrophobic magnetite nanoparticles, can be actuated magnetically.
Bismuth telluride and its alloys are unique materials. They are the best thermoelectric materials known today, and they are as important to the thermoelectric industry - for cooling and energy generation applications - as silicon is important to the electronic industry. It has been predicted theoretically that structuring bismuth telluride into crystalline ultra-thin films (with the thickness of few nanometers) would lead to a drastic improvement of the thermoelectric figure of merit, which defines the efficiency of the thermoelectric energy conversion. The improvement comes as a result of the strong quantum confinement of charge carriers and reduction of the thermal conductivity. In addition to their thermoelectric applications, bismuth telluride thin films recently attracted attention as promising topological insulators - a newly discovered class of materials with unusual properties. Researchers have now succeeded in 'graphene-inspired' mechanical exfoliation of atomically-thin crystals of bismuth telluride.
Materials that can produce electricity are at the core of piezoelectric research and the vision of self-powering machines and devices. Nanotechnology researchers are even pursuing nanopiezotronics devices that have the potential of converting biological mechanical energy, acoustic/ultrasonic vibration energy, and biofluid hydraulic energy into electricity, demonstrating a new pathway for self-powering of wireless nanodevices and nanosystems. In addition to miniaturizing piezoelectric devices down to the nanoscale, nanotechnology is also contributing to making next-generation devices more effective. Piezoelectric ceramics for instance generate electrical charge or voltage when they experience stress/strain, and thus are highly efficient at converting mechanical energy into electrical energy. However, ceramics are rigid, which greatly limits the applicability of the energy harvesting. Researchers have now demonstrated that high performance piezoelectric ceramics can be transferred in a scalable process onto rubber or plastic, rendering them flexible without any sacrifice in energy conversion efficiency.
One important aspect of clothing comfort is thermo-physiological comfort. By adjusting the transport of heat and moisture through a fabric, thermo-physiological comfort can keep people comfortable with regard to temperature and moisture. Some hydrophobic fabrics have deficiencies in this area. Take wool. Wool is one of the best insulating fibers known to man - while at the same time being light and soft. The quality that distinguishes wool fibers is the presence of a fatty, water-repellent outer layer that surrounds each fiber. Therefore, the water absorption and sweat venting properties of wool fiber are not very good, which affects the wearing comfort of wool textiles. The wool hydrophobic surface layer is also a barrier to anticrease finishing, dyeing, and grafting of hydrophilic agents, which is an issue in trying to add smart functionalities to wool fabrics.
Researchers have now developed a simple method for fabricating environmentally stable superhydrophilic wool fabrics. They applied silica sols to natural wool fibers to form an ultrathin layer on the surface of the fibers.