In a short news release, the Institute of Physics reports that smart holograms, which use materials called hydrogels that shrink or swell in response to local environmental conditions, can be used to monitor many physical conditions than three years ago. These smart holograms could soon be used 'by diabetics to check their blood-sugar levels, by patients with kidney disorders to check on adrenaline levels or by security forces to detect chemicals like anthrax after a terrorist attack.' And today, moisture sensitive sensor holograms are used to verify the presence (or absence) of free water in aviation fuel. But read more...
You can see above an example of how these smart holograms can be used. "Smart holograms are recorded in polymers specifically designed to change in response to physical, chemical or biological stimuli thanks to the incorporation of functional or reactive groups. Thus, the hologram itself provides both the polymer matrix that responds to a particular stimulus or substance one is trying to measure, and also the means to visualize the response. For example, a green smart hologram sprayed with ethanol to simulate a Breathalyser test for alcohol on expired breath turns blue when the polymer contracts. The frames were obtained at 20 ms intervals." (Credit: Smart Holograms Ltd, via Physics World) Here is a link to a larger version of this picture.
The Institute of Physics reports that "Smart Holograms, a spin-out company from the Institute of Biotechnology at Cambridge University, has already developed a hand-held syringe to measure water content in aviation fuel tanks -- necessary because aeroplane engines are liable to freeze mid-air if there is more than 30 parts water to million fuel."
The company uses the research results of Professor Chris Lowe, Director of the Institute of Biotechnology and Professor of Biotechnology at Cambridge University in the UK, who is one co-founder of this start-up. Here is a link to his research about holographic biosensors.
Chris Lowe just wrote an article with Cynthia Larbey, Managing Director of Smart Holograms, published by Physics World, "Holography gets smart" (Volume 21, Number 2, February 2008).
This long article features a very exhaustive history of holography and how "it was developed in 1947 by the Hungarian-born physicist Dennis Gabor, for which he was awarded the 1971 Nobel Prize for Physics." Please read the whole article for more information about 'regular' holograms, the ones you now found on your credit cards.
Now, let's move to smart holograms. "In a smart hologram, a suitable complementary receptor is attached to the polymer matrix of the photographic emulsion such that the polymer undergoes a physical or chemical change when a substance of interest (called the analyte) binds to it. Thus, in principle, any physical, chemical or biological stimulus that interacts with the smart polymer will generate observable changes in the wavelength (i.e. colour), intensity (brightness) or encoded image of the reflection hologram."
And here are additional details. "The active component in such a 'smart' hologram is normally a 3D polymer network called a hydrogel, which is a material that is very good at absorbing water and can swell anywhere up to 1000% of its original volume. By incorporating a hologram throughout the volume of a hydrogel, holographic gratings can be fabricated that respond to, for example, humidity, water, solvents, dissolved gases, ions, metabolites, drugs, antibiotics, sugars or enzymes. In most cases, the binding of the target analyte to the receptor in the hydrogel generates either a change in charge status, a covalent or non-covalent 'crosslink' between neighbouring polymer chains, or a change in secondary interactions involving hydrogen bonding or hydrophobicity. What this means is that relatively small perturbations in environmental conditions can cause macroscopic changes to the volume of the hydrogel by it absorbing different amounts of water."
This is a very interesting article which is worth reading. But let's end this post by summarizing what are some of the advantages of sensor holograms according to this page at Smart Holograms. "They are virtually impossible to reverse engineer or replicate; results are fast and real-time: they are 'format-flexible' to meet individual requirements -- they can be integrated into packaging labels, fibre optic catheters, sub-dermal implants, for example; they do not require a power source; and the manufacturing process is easily integrated into existing supply chains."
Sources: Institute of Physics news release, February 4, 2008; and various websites
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