Laser-based processes may help create better artificial joints, arterial stents

Washington, September 16 (ANI): Scientists hope that laser-based processes may help create arterial stents and longer-lasting medical implants 10 times faster, and less expensively.

Yung Shin, a professor of Mechanical Engineering and director of Purdue’s Center for Laser-Based Manufacturing, stresses the need for new technologies to meet the huge global market for artificial hips and knees, insisting that the worldwide population of people younger than 40 who receive hip implants is expected to be 40 million annually by 2010, and double to 80 million by 2030.

Besides speeding production to meet the anticipated demand, Shin says that another goal is to create implants that last longer than the ones that are made presently.

“We have 200,000 total hip replacements in the United States. They last about 10 years on average. That means if you receive an implant at 40, you may need to have it replaced three or four times in your lifetime,” he said.

In one of their techniques, the researchers deposit layers of a powdered mixture of metal and ceramic materials, melting the powder with a laser and then immediately solidifying each layer to form parts.

Shin says that, given that the technique enables parts to be formed one layer at a time, it is ideal for coating titanium implants with ceramic materials that mimic the characteristics of natural bone.

“Titanium and other metals do not match either the stiffness or the nature of bones, so you have to coat it with something that does. However, if you deposit ceramic on metal, you don’t want there to be an abrupt change of materials because that causes differences in thermal expansion and chemical composition, which results in cracks. One way to correct this is to change the composition gradually so you don’t have a sharp boundary,” Shin said.

The gradual layering approach is called a “functionally gradient coating”.

The researchers have revealed that they used their laser deposition processes to create a porous titanium-based surface and a calcium phosphate outer surface, both designed to better match the stiffness of bone than conventional implants.

The laser deposition process enables researchers to make parts with complex shapes that are customized for the patient.

“Medical imaging scans could just be sent to the laboratory, where the laser deposition would create the part from the images. Instead of taking 30 days like it does now because you have to make a mold first, we could do it in three days. You reduce both the cost and production time,” Shin said.

According to the researchers, the laser deposition technique lends itself to the requirement that each implant be designed specifically for each patient.

“These are not like automotive parts. You can’t make a million that are all the same,” Shin said.

He says that the process creates a strong bond between the material being deposited and the underlying titanium, steel or chromium.

The researcher further reveals that tests have shown that the bond is at least seven times as strong as industry standards require.

Using computational modelling, the researchers simulate, study and optimise the processes.

The researchers, however, admit that more studies are required before the techniques are ready for commercialisation.

They have revealed that their future work will involve studying “shape-memory” materials that are similar to bone and also have a self-healing capability for longer-lasting implants.

They are also working on a technique that uses an “ultra short pulse laser” to create arterial stents, which are metal scaffolds inserted into arteries to keep them open after surgeries to treat clogs.

Since the laser pulses last only a matter of picoseconds, or quadrillionths of a second, they do not cause heat damage to the foil-thin stainless steel and titanium material used to make the stents.

The laser removes material in precise patterns in a process called “cold ablation”, which turns solids into a plasma. The patterns enable the stents to expand properly after being inserted into a blood vessel. (ANI)

Lunar rock-like material may be used to build future Moon colonies

Washington, Jan 10 (ANI): Students from the College of Engineering at Virginia Tech in the US have made highly durable bricks composed of a lunar rock-like material, which one day might be used to build dwellings in colonies on the moon.

The invention won the In-Situ Lunar Resource Utilization materials and construction category award from the Pacific International Space Center for Exploration Systems (PISCES).

The team of students, under the advisement of Kathryn Logan, a professor in the materials science and engineering department, designed the brick as a potential building tool for future colonies on the moon.

Initially designed to construct a dome, the building material is composed of a lunar rock-like material mixed with powdered aluminum that can be molded into any shape.

Design work on the early-development lunar bricks was based on previous work by the College of Engineering student team’s adviser Kathryn Logan, a professor of materials science and engineering and the Virginia Tech Langley Professor at the National Institute of Aerospace in Hampton, Virginia.

Logan’s prior research entailed mixing powdered aluminum and ceramic materials to form armor plating for tanks funded through a Department of Defense contract.

“I theorized that if I could do this kind of reaction to make armor, then I could use a similar type of reaction to make construction materials for the moon,” Logan said.

Since actual lunar rock, known as regolith, is scarce, the students used volcanic ash from a deposit on Earth along with various minerals and basaltic glass, similar to rock on the lunar surface, according to Eric Faierson, a doctoral student who led the Virginia Tech team.

During initial experiments, the simulated regolith and aluminum powder were mixed and placed inside a shallow aluminum foil crucible.

A wire was inserted into the mixture, which was then heated to 2,700 degrees Fahrenheit triggering a reaction called self-propagating high-temperature synthesis (SHS), according to Logan.

The reaction caused the material to form a solid brick. A ceramic crucible was used in later experiments to form complex curved surfaces.

Once the student team had created a brick, they found that it was almost as strong as concrete under various pressure tests.

According to Faierson, one-square inch of the brick could withstand the gradual application of 2,450 pounds.

This strength would enable it to withstand an environment where gravity is a fraction of the pull on Earth. (ANI)