Nanotechnology Can Help Keep the DART Clean
Revolutionary technology has resulted from visionaries and entrepreneurs who have “thought big.” However, in the case of antimicrobial and self-cleaning technologies, reducing materials size to the nanoscale can reduce the cost and maintenance of our transportation system.
Nanomaterials are any materials that are 1-100 nm in one dimension, which means they have properties that depend on their size. These materials can have special properties, which are different from their bulk counterparts. For example, cadmium selenide quantum dots can absorb different wavelengths of light between 400-700 nm, depending on the diameter of the quantum dots which can range from 2-7 nm. Other common materials such as titanium dioxide, which is used in household items such as sunscreen and paint, can absorb different wavelengths of light depending on their shape. Nanomaterials have wide-ranging applications in photovoltaics, sensors, catalysis, and medicine.
In medicine, nanomaterials are often used for their antibacterial properties. For athletes who train hours in socks and shoes, antibacterial socks interwoven with silver nanoparticles help fend off odor-causing bacteria. Another use of antibacterial titanium dioxide nanoparticles is coating of surfaces in public spaces such as turnstiles, arm rests and poles on trains. In the case of silver nanoparticles, its ions will attach to bacteria and cause cell lysis (breakdown and eventual death). The nano size helps particles dissolve into solution and be effective as an antimicrobial material. Introduction of nanomaterials into biological systems may cause concern for safety. In the case of titanium dioxide particles in sunblock, they have proven to be harmless to humans. But because each material is different, there are ongoing studies regarding safe usage of nanomaterials .
Nanomaterials can also be used to repel dust from collecting on windows. Coatings of nanoscale rods, tubes, or spheres reduce the amount of water or dust that lands on a surface. This self-cleaning material reduces the maintenance needs, which is particularly useful for highly trafficked spaces such as train cars. Nanomaterials are good at repelling water and dust primarily because they are often surrounded by surfactants, which consist of long-chain hydrocarbons. These surfactants are non-polar; thus are not attracted to polar water molecules. This effect is also observed in Nature. Water droplets bead up and roll off of lotus leaves due to the waxy and spiky surface of the leaves. The waxy (fuzzy) surface of peaches relies on the same type of chemistry to repel water.
Another use for nanotechnology in the transportation industry is to create smart windows. Recently, researchers have embedded indium tin oxide nanocrystals in niobium oxide glass to modulate how much sunlight can pass through a window . The new coating can regulate the transmission of visible light as well as near-infrared light, which is invisible to the naked eye but produce heat. An electric switch allows the window to absorb or deflect light, due to a coupling of the electrical and optical properties of the material. Both indium tin oxide and niobium oxide change color when electrical current flows through them. Indium tin oxide is widely used in photovoltaic technologies, converting solar rays into electricity, as well as in smartphone touchscreens. In smart windows, when current flows through the material, indium tin oxide absorbs heat from the sun while niobium oxide changes to a darker color, thus blocking light from passing through and providing shade.
The solutions to tomorrow’s big problems of energy and sustainability may come from small particles. For large public places such as train cars, the usage of nanomaterials can reduce energy and maintenance costs as well as helping to manage public health.
