Category: Materials

A shape-memory alloy is an alloy that remembers its original, cold-forged shape: returning to the pre-deformed shape when heated. Shape-memory alloys have many applications such as medicine. One example of that is dental braces, which are are devices used in orthodontics that align and straighten teeth and help to position them with regard to a person’s bite, while also working to improve dental health. The application of braces moves the teeth as a result of force and pressure on the teeth. There are four basic elements that are needed in order to help move the teeth. In the case of traditional metal or wire braces, one uses brackets, bonding material, arch wire, and ligature elastic, also called an “O-ring” to help align the teeth. The teeth move when the arch wire puts pressure on the brackets and teeth. This movement needs to be done slowly otherwise the patient risks losing his or her teeth. This is why braces are commonly worn for around two and a half years and adjustments are only made every three to four weeks.

A shape memory alloy is a group of metallic materials that can return to some previously defined shape or size when subjected to the appropriate thermal procedure. That is, shape memory alloys can be plastically deformed at some relatively low temperature and, upon exposure to some higher temperature, will return to their original shape. Materials that exhibit shape memory only upon heating are said to have a one-way shape memory, while those which also undergo a change in shape upon recooling have a two-way memory.  There are examples of SMAs used in safety devices which will save lives in the future. Anti-scalding devices and fire-sprinklers utilizing SMAs are already on the market. The anti-scalding valves can be used in water faucets and shower heads. After a certain temperature, the device automatically shuts off the water flow. The main advantage of Nitinol-based fire sprinklers is the decrease in response time. The shape-memory element expands as it is heated, forcing a bolt to break, thereby opening the sprinkler valve.

Biblio:

http://www.azom.com/article.aspx?ArticleID=134

http://www.freepatentsonline.com/y2010/0025050.html

Chevy in releasing their new 2013 corvette created a new smart material to try and making the car lighter. This material replaces the heavier motorized actuator to open and close the hatch vent that releases air from the trunk with a new smart metal alloy. This allows the trunk lid to close more easily than on the previous models where trapped air could make the lid harder to close. It does this using smart memory alloys, made from copper aluminum and nickel. In the new Corvette, the shape memory alloy wire opens the hatch vent whenever the deck lid is opened, using heat from an electrical current s. When activated, the wire contracts and moves a lever arm to open the vent, allowing the trunk lid to close. Once the trunk lid is closed, the electrical current switches off, allowing the wire to cool and return to its normal shape, which closes the vent to maintain cabin temperature. This new material is about 2 pounds lighter than its predecessor. As well, this material is cheaper to produce, which saves the company money. In terms for the environment, it is beneficial because it uses less energy to maintain temperature in the car, which saves on lots of energy when you consider all the amount of cars that would be sold.

Currently, millions of tons of fossils fuels are combusted to produce energy through converting thermal energy to electric energy or kinetic energy in an inefficient way. Fossil fuel engines run at approximately 40% efficiency, with the other 60% being lost to the environment. A recent discovery has been made by scientists at Stanford University in the application of silicon nanowires as producers of electricity. A current property of thermoelectric materials is the conduction of electricity when one end of the material is warmer than the opposite end, generating electricity. However, in most cases producing such a material is either very expensive or requires considerable costs to keep one end warmer than the other as since many materials that conduct electricity well also conduct heat well and so near equal temperature is established at both sides. The break through to this dilemma comes with the development of silicon nanowires. These tiny wires have the intriguing property of electrical conductivity but highly reduced thermal conductivity, allowing for significantly increased efficiency in thermoelectric applications. The idea is that the energy lost to the environment primarily to heat escaping, can be converted into electrical energy, increasing the efficiency of fossil fuel usage.

 http://spie.org/Images/Graphics/Newsroom/Imported/1087/1087_fig1.jpg

The applications for this discovery are far reaching, as it affects nearly all electronic products, any engine using fuel to evolve thermal energy, and even the efficiency of batteries. A further benefit of the application of this technology comes with the fact that the silicon industry is already well established and so integration of procedures to produce silicon on the nano scale for wiring can be done faster and in a more feasible fashion. In addition, silicon is not considered a rare material, like platinum or gold, but actually exists in a vast quantity in Earth’s crust.

Source: http://www.stsm.ir/resources/10302-16101387085210silicon%20nanowire%20thermoelectrics.pdf

Marchon Eyewear have developed a range of eyeglass frames featuring a revolutionary new material. The frames are made from a shape memory alloy of titanium under the trademark name, Flexon. Frames made from this alloy are noticeably lighter and more flexible than other frames. The eyeglass frame can be bent, twisted and contorted in many ways but will always spring back to its original shape, as seen in the following video:
Flexon Bendy Glasses Frame

Regular eyeglasses will often become bent and not sit straight on their user’s face after daily use and it can prove very difficult to return them to their original shape. However, this is no longer a problem with frames made from Flexon as it is not possible to permanently distort their shape.

Marchon Eyeglasses has designed glasses appealing to a range of men, women, and children whilst expanding its designer portfolio to include such names as: Calvin Klein, Fendi, and Valentino.

Eyeglasses,however, are not the only useful utilization of shape memory alloys (SMA) of titanium, such as Flexon. Nitinol is a  SMA with similar properties to that of Flexon and can be used in the underwire of bras, golf clubs, and novelty products (magicians bending spoons). Some of its more beneficial uses are in medical situations in which it can be used to locate/mark breast tumors, stents (a collapsed stent is inserted into a vein and then heated so it returns to its original shape and helps to improve blood flow), and also in orthopedic implants as it is highly bio-compatible.

As seen above, despite its value to daily life in the form of resilient glasses frames, this SMA also has many other worthy uses in medical situations.