Interested In Science?

Now, I know most (actually at this time and date, it’s all!) of the blogs and pages written here are strongly pertaining to nanomaterials and plastic electronics, but this one I feel needs special attention because it is such a simple yet essential component of any electrical circuit. The power supply!

I have read literally hundreds of papers on dozens of different aspects of plastic electronic componentry, from molecular wires to OLEDs that can also act as light harvesting devices (photovoltaics), i.e. the simplest to the more complicated issues. I had not heard of any developments regarding a nano-scale power supply - or nanobattery, probably because I hadn’t really considered it. I have now…

One of the most recent RSS Feeds from NewScientist regards the invention of a biological nanobattery. It sounds absurd at first, but when the principle of a battery is analysed it makes sense.

A battery is just a combination of materials that allow the semi-permanent storage of a charge, due to the nature of the differences between the materials’ potential differences and electromotive forces.

I was curious as to how this principle could be adapted and implemented on the nano-scale, and was pleased to see such a simple process described. NASA decided to investigate the use of the protein ferritin, an iron-based compound that can carry either a negative or positive charge. Ferritin already has a use in materials science as a reagent in the preparation of carbon nanotubes, but its use as a major constituent of a nano-scale device is novel.
NASA’s proposed capacitor is based on a system of layers of oppositely charged ferritin, deposited by spin coating one on top of the other, until sufficient layers are present to enable charge storage between them. Unfortunately the only further information I could find on this research is a rather legal-term-dense patent application (see the NewScientist website), but if I find anything more about it I will share it here asap.

To be thorough on the subject I did a quick literature search on nanobatteries, and was pleased and somewhat surprised to discover that there has been a significant amount of research done - and this ferritin-based cell is not the only sort out there.

In 2004 mPhase Technologies in association with Bell Labs claimed to have successfully prepared the first nano-battery. A report said the battery was
“…based on a Bell Labs’ discovery that liquid droplets of electrolyte…stay in a dormant state atop…nanograss until stimulated to flow…triggering a reaction that produces electricity”
Unfortunately, yet again, I couldn’t find any useful journals or articles relating to this report, but I shall keep looking - and if anybody out there knows something, please drop a comment!
Nano-batteries are an inevitable feature of a nano-tech device, and since these devices are becoming more and more popular I think any developments in this power-supply area are worthy of reporting.

interestedinscience.com © 2007

A break from plastic electronics here, but not from chemistry, or even nanomaterials!

A group of scientists in Alberquerque, New Mexico, have synthesised superparamagnetic nanoparticles in a material with the functional ability to bind with cancerous cells. This allows the cancerous cells to then become themselves magnetized. A magnetic probe can then be used to collect the cancerous cells, removing the need for repeated invasion of the host to collect biopsies, which can be a painful as well as prove inaccurate.

A biologically compatible material is impregnated with these nanoparticles of magnetic iron oxide, and then coated with an antibody that binds indiscriminately with some cancer-based chemical. Hence, the material seeks and binds with the cancer, and the nanoparticulate superparamagnetic iron oxide magnetizes the system, enabling detection and capture with a magnetic probe.

The use of magnetic nanopartcles is common place now as part of several analytical procedures in medicine, the most common and famous being in MRI (magnetic resonance imaging). Here nanoparticles of iron oxide, such as the commercially available Feridex I.V. by Advanced Magnetics Inc., are used as contrast reagents and can be made to specifically target certain organs (Feridex I. V. targets liver lesions). Another use of magnetism in medicine is in the use of SQUIDs (superconducting quantum interference devices) to detect nanoparticles which have been attached by a similar method to above to T-cells, which allows an early and non-invasive method of detection of rejection of a transplant organ. The SQUID array is also used to allow an image of the targeted cells to be captured, and is so sensitive that only a few milligrams of the nanoparticles need to be injected.

I hope that this technology proves to be as useful (if not more!) than the paper suggests, as recently nanomaterials have got a bit of bad press due to their as-yet unknown long-term side-effects. I have personally done some work with nanomaterials (well, qunatum dots to be more precise) involving tagging with fluorescent dyes, and I must say how visually stunning the results are, as well as the ease of preparation. Unfortunately our exercise was purely academic (a ‘can we do it?’ mentality if you like) so there are no real results to report. However! This does not shake my belief that nanomaterials have still got a lot to offer, and although the side-effects are unknown, I hope the exciting research continues unabated.

For more on the aforementioned magnetization of cancer cells see Phys. Med. Biol. 2007 52 4009 and the article at NewScientist.co.uk

For more information on the use of SQUID arrays for determining transplant rejection see J. Magn. Magn. Mat. 2007 311 429.

For more information about nanomaterials and nanotechnology in general see the latest magazine edition of NewScientist.

interestedinscience.com © 2007

In the latest edition of the journal Science there features a report on the successful preparation of a plastic photovoltaic cell that reaches efficiencies of 6.5%, a record for this type of device. Alan Heeger and colleagues from the University of California, Santa Barbara, in collaboration with scientists from Gwangju Institute of Science and Technology, have sandwiched two polymers together around a layer of transparent titanium oxide, to create a ‘tandem cell’.

The reason the efficiency of this device is so high is that the two different polymers absorb in different regions of the solar emission spectrum i.e. electromagnetic radiation emitted from the sun, meaning they can collect more light energy. The titanium oxide layer is completely transparent to these energies of light, and thus allows the rear polymer to absorb light that isn’t absorbed by the front polymer. The titanium oxide is an integral component because of this transparency.

‘Tandem cell architectures’ have been attempted before but without this high efficiency; partly due to the two polymers absorbing the same energies of light, partly due to poor processing methods allowing the polymers to mix, but also down to the incorporation of only a semi-transparent layer sandwiched between the layers, severely inhibiting the absorption capabilities of the rear plastic film.

Schematic of the tandem cell, taken from Science 2007 317 222-225

Some scientists believe that 6.5% effective power conversion is likely beatable in the very near future, with figures closer to 10% being rumoured. This new tandem cell could herald a break-through in the technology. Due to the nature of the materials that constitute these devices, their production is cheap, with large flexible surfaces being the obvious goal.

Keep checking interestedinscience.com for any updates on this subject.

For more on this topic, see gizmodo.com or technologyreview.com

See {Science 2007 317 222-225} for the original article.

interestedinscience.com ©  2007

OK, so not directly a development in science but more good impetus for the industry and general research.

Universal Display Corporation have been awarded US$200K by the US DOE (Department of Energy) to aid their research into SOLED™ (stacked organic light emitting diodes) technology, in an attempt to produce WOLED™ technology (white OLEDs) of high efficiency. Also described by a second grant is the aim to increase the performance of their PHOLED (phosphorescent OLEDs) technology with increased size of display panel. Says President and Chief Operating Officer of UDC Steven Abramson:

“We are pleased to continue our work with the US Department of Energy to demonstrate further advancements in our white OLED technology.”

I bet they are! OLEDs are the science behind a new flat-panel screen technology that will soon take over LCD (liquid crystal display), TFT (thin film transistor) and Plasma screens.

Many scientists envision a highly flexible, paper-thin sheet of organic material which can be used in much the same way as todays TFT screens are, but which display a higher resolution for a wider viewing angle, as well as being cheaper to process. Screens made of such material are already being incorporated into consumer electronics, such as phones and PDAs, flat screen televisions and, my favourite, the Aston Martin DB9 instrumentation panel.

The science behind these screens is fascinating (I know, my thesis is partly based on it!) and the fact that such an advanced technology, only conceived at most 12 years ago, is now in full production is simply fantastic. The futuristic look and the projected low costs is a massive attraction with this technology, but nothing is as attractive as their potential power efficiencies.

Example OLED device, taken from www.mygadgetbag.com

Keep checking these pages as this is one subject I will definitely be coming back to.

interestedinscience.com ©  2007

This is a new blog focusing on developments in science. Content is en route, and any comments or queries are eagerly received.

Hopefully there’ll be something worth reading here soon!

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