Manufacturing Bits: March 28

Dental implants; multi-parameter microscopes; ptychography.


Dental implants
Borrowing some of the same processes used in the semiconductor industry, the Peninsula Schools of Medicine and Dentistry and the University of Plymouth have developed new nanocoating materials for dental implants.

Some three million Americans have dental implants, according to the American Academy of Implant Dentistry (AAID). This number is rising by 500,000 a year, according to AAID. But 5% to 10% of all dental implants fail, due to poor connection to the bone and other issues. The main reason for dental implant failure is peri-implantitis, an inflammatory process affecting the tissues around the dental implants.

In response, the Peninsula Schools of Medicine and Dentistry and the University of Plymouth have devised new dental implant materials that promise to reduce the risk of peri-implantitis. Researchers devised a combination of silver, titanium oxide and hydroxyapatite nano-coatings.

First, researchers obtained a titanium alloy sheet. The sheet was cut using a laser, enabling tiny titanium discs. The discs were 15nm in diameter and 1mm thick. Then, the discs were polished and cleaned in an ultrasonic bath. The discs were coated with gold using electroplating. The anodization technique was used to create a thin oxide layer on the surface. And finally, the discs were placed in a furnace to improve the stability of the coatings.

Alexandros Besinis, a lecturer in Mechanical Engineering at the School of Engineering at University of Plymouth, said: “Current strategies to render the surface of dental implants antibacterial with the aim to prevent infection and peri-implantitis development, include application of antimicrobial coatings loaded with antibiotics or chlorhexidine. However, such approaches are usually effective only in the short-term, and the use of chlorhexidine has also been reported to be toxic to human cells. The significance of our new study is that we have successfully applied a dual-layered silver-hydroxyapatite nanocoating to titanium alloy medical implants which helps to overcome these risks.”

Multi-parameter microscopes
The National Physical Laboratory (NPL) has developed a multi-parameter microscope.

The technology from NPL is called simultaneous topographical, electrical, chemical and optical microscopy (STEOM). It could be used for optoelectronics, solar cells, sensors and transistors.

STEOM is a non-destructive technique, which combines plasmonic optical signal enhancement technology with electrical-mode scanning probe microscopy. It maps the morphology, chemical composition and photoelectrical properties at 20nm resolutions and below. Plasmonic optics combine electronics and photonics, which explores the interactions between electromagnetic waves and matter. Scanning probe microscopy forms images of a surface. This is done by using a physical probe.

The STEOM apparatus for multi-parameter characterization (Source: NPL)

The STEOM apparatus for multi-parameter characterization (Source: NPL)

The Institut Fresnel, IBM and the U.S. Department of Energy’s (DOE) Argonne National Laboratory have developed a new form of X-ray metrology called single-angle Bragg ptychography.

The technique provides three-dimensional images of stressed materials. More specifically, the technology provides a better picture of how planes of atoms shift and squeeze under stress, a series of events that could help enable current and future chips.

The technique makes use of X-ray diffraction, a metrology technology used to explore single-crystal and thin-film materials. In X-ray diffraction, a sample is hit with X-ray beams and the atoms within the sample scatter. This, in turn, produces a signal on a detector. Then, a method called Fourier analysis is used. It converts the signals to a series of waves with peaks and valleys, according to Argonne National Laboratory.

X-ray diffraction is not enough, however. It only measures the height of the waves, not the phases. For this, researchers used ptychography, a technique that solves the phase problem. It is able to recover phase information using redundant sampling from the same region of a sample, according to Argonne National Laboratory.

Bragg single-angle ptychography (Image by Robert Horn/Argonne National Laboratory.)

Bragg single-angle ptychography (Image by Robert Horn/Argonne National Laboratory.)

In the lab, researchers shifted the X-ray beam position in the metrology tool. Then, they image some 60% of the space between beam positions, enabling them to gain information about the phase. “Most diffraction techniques, including some ptychographic ones, really only give a 2D representation of the sample of interest,” said Stephan Hruszkewycz, a materials scientist at Argonne National Laboratory. “This technique also makes fewer requirements in terms of the instrument technology than comparable techniques for generating 3D information about materials.

“In order to really see and understand the strain in real space, you need information on both intensity and the phase,” he said. “What we needed was a trick to retrieve the missing phases of the diffraction pattern.”

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