News highlights of the week - 14th Feb 2009

A week is a long time in optics because the science and technology moves at a rapid pace. Here are a few highlights from the week's news, which include mimicking the way nature captures light without reflection, and how lasers can be used to heal wounds.

Salmonella typhimurium

Outbreaks of salmonella contamination can cost any food business a lot of money in downtime and disinfection, and current detection methods require samples to be analysed in a lab, which can take many days. Now researchers at Iowa State University have devised a technique that could lead to portable analysers capable of delivering results in just two hours. Surface samples are removed with adhesive tape and soaked in a mixture containing a genetic marker which binds with salmonella and fluoresces under ultraviolet light, thereby indicating the presence of potentially deadly contamination in a quick and easy process.

A more advanced form of biological testing is embodied by the term lab on a chip, which describes the manipulation of individual particles, such as cells and viruses, on the microscopic scale. Researchers from the University of Bordeaux in France have come up with a new optical tool which can control the movement of biological particles around a chip. They moved jets of liquid along the path of a laser beam and used a second beam to selectively divert droplets of interest.

Medical science may one day have an optical tool which is something that could be right out of the pages of a science fiction novel: laser beams that can heal wounds. A photo-sensitive dye applied to a surgical incision in skin was shown to promote healing under high intensity laser light. The likely mechanism is the transfer of electrons from the dye to the collagen in the skin, which accelerates the process of chemical bonding. This nano-suturing could replace conventional suturing where stitches might cause further complications or infection, such as in eye surgery. It might also be used to speed up healing and reduce scarring.

Scientific progress often results from looking at the way nature has solved a problem. Researchers at the AMOLF Institute in Eindhoven did just that in an attempt to improve upon anti-reflection coatings and increase the light collection efficiency of optical components. Inspired by the way moths' eyes work, they grew nanowires of varying lengths to produce a single material with a refractive index that varied with depth. The vast majority of light in their experiments was transmitted through the material, with very little reflected at the surface or absorbed and scattered in the material itself. This research could lead to solar cells that collect almost 100% of incident sunlight and thereby improve their efficiency.

Solar energy researchers in Japan have also been looking to nature for better ways to capture the energy of the sun, by actually using natural photosystems. They coupled the photosystem of a blue-green algae to a gold electrode, using a molecular "wire" in the form of a hydrocarbon chain. The system achieved energy conversion efficiencies close to that of natural systems, which are some of the most efficient at converting photons into chemical energy.

Observing photosynthesis in action was the aim of scientists at University College Dublin in Ireland, who used high-speed lasers to study the energy transfer mechanism between electrons in photosynthetic systems. A better understanding of these processes could lead to new and improved solar energy products in the future.

Los Alamos researchers have been looking at improving solar cell efficiency by taking a closer look at carrier multiplication, a process whereby single photons produce multiple charge carriers. Photons with greater energy than is required to generate a charge pair in a conventional solar cell, lose their excess energy to lattice vibrations. They could be more efficient if that otherwise wasted energy was used to generate more charge carriers, which this group showed was possible with a certain type of semiconductor nanocrystal.

As always, you can find more optical science and technology news by going to the news page at OpticalFutures.com.