Smart Holograms Used As Biosensors

By Roland Piquepaille

In this short article, eWEEK writes that the next generation of biosensors will consist of small holograms costing only fractions of a cent. Prototypes developed by a U.K. company, aptly named Smart Holograms, include contact lenses that monitor glucose levels or thin badges that detect alcohol levels. Not only these holograms used as sensors will be cheap to produce, they'll also require less training for nurses or police officers. This is because these holograms can be designed to show results graphically, such as morphing into an image of a green car if someone subjected to breath analysis is sober and can drive. Read more...

Here are selected quotes from the eWEEK article.

Prototypes have already been made for contact lenses that monitor glucose levels, thin badges that detect alcohol levels, and sticks that can tell, instantly, if milk has spoiled or become contaminated. The technology promises to be quicker and cheaper than tests used today. It will also require less training, because the hologram itself can be designed to show results graphically.

A test showing that fuel has been contaminated with trace amounts of water reads "dry" or "wet." In a breath alcohol test intended for police offices, suspects breathe onto tiny cards that either show a green automobile or a red X, establishing whether a person is sober enough to drive.

This technology looks cheap and promising, according to Chris Lowe, a professor at Cambridge University, and co-founder of Smart Holograms.

One advantage of the technology is that each hologram costs only a fraction of a cent to produce. Another is the wide applicability. The holograms can detect pH to four decimal places and chemical concentrations of hormones and other biologically important substances. The samples tested do not need to be pure: The holograms can work in milk or even in stool samples from newborns, said Lowe.

Now, let's turn to the company itself to see how holograms can be turned into biosensors. Here are some explanations provided on this page whose title is "Creating a Sensor Hologram."

Sensors that rely on the ability of "smart" polymers to swell or contract when in contact with specific biological reagents, chemicals or physical forces, sometimes called volume holograms, are of significant interest. For example, bright wavelength changes produced by holograms fabricated in hydrophilic polymers offer immediate advantages as a facile and reliable means of measuring volume changes. Hologram gratings capable of exhibiting spectral effects from volume changes need to be of the so-called "Denisyuk" type.

For more information about Yuri Denisyuk, you can read this brief history of the holography.

[The figure above] illustrates the experimental set-up used to create Denisyuk-type holograms. Laser light returning from a plane mirror creates a classical standing wave pattern of nodes and antinodes or interference fringes spaced half a wavelength apart. The standing wave pattern is recorded in the polymer matrix that has been coated on a plastic substrate or glass microscope slide. After a conventional photographic development step, the fringe pattern is represented as a distribution of ultrafine (<20 nm diameter) grains of silver.

Is this technology as accurate as told by its promoters? We'll see. However, it really seems it has a serious cost advantage over current technologies, so it has the potential to become widely used in a few years.

Sources: M.L. Baker, eWEEK, February 19, 2005; Smart Holograms website

Related stories can be found in the following categories.

• Biotechnology
  
• Holograms
  
• Medicine
  
• Nanotechnology
  
• Police
  
• Sensors