This naturally raises the question of how these substance "libraries" are best stored. In order to ensure effective screening, it is important that both the individual active substances and other biological samples occurring in similar quantities – for example traces of DNA and oligonucleotides – are stored safely, can be located quickly and can be made available for testing without delay.

British supplier TTP Labtech Ltd. of Melbourn, Cambridgeshire, UK offers a remarkably effective solution with a footprint of less than two square meters that can replace an entire air-conditioned storage room. At the heart of the system known as comPOUND are 26 lightweight and complex carousels made of Baydur® 61 FR polyurethane from Bayer MaterialScience AG, each of which can house around 4,000 individual samples.

The concept behind the new "safe" for the crown jewels of pharmaceutical and biochemical labs is brilliant in its simplicity – each of the approximately 100,000 samples in the safe, which has the dimensions of a small broom cupboard, can be moved from its storage position into an output pipe by means of a jet of compressed air.

This method is fast, on average taking only five seconds to move the 1.4 mm3 microtubes from their storage position to the output compartment. It also saves space, since the jet of compressed air replaces the robot arm which is normally used for this type of product and takes up considerable space.

To manage the in excess of 100,000 samples housed in such a confined space, an intelligent logistics concept is not enough in itself. A suitable material is also required for turning the idea into reality. To be able to handle the microtubes at speed, they need to be stored in modules that can not only be moved quickly, but also contain an exceptionally high number of storage holes.

These two requirements in themselves significantly limit the number of possible materials. The ideal material must be low in weight and able to assume complex geometries. Metals are ruled out because of weight considerations, while thermoplastics are equally unsuitable, since the geometry of a molding with its thousands of holes is too complex for the conventional injection molding process.

The lab experts from Melbourn found the solution to this problem in the form of Baydur® 61 FR from Bayer MaterialScience. With this polyurethane integral skin foam with its porous core and smooth, easily cleaned surface the 26 carousels of the ComPOUND “safe” with a diameter of 95 cm and height of 52 mm weigh just 15 kg. The 4,000 storage holes in each of these carousels, like the aluminum hubs, are molded by the manufacturer of the polyurethane moldings, Rim Plastics Technology Ltd., Basildon, UK, in a one-shot procedure without any need for costly secondary finishing. The cycle time per carousel is only 10 minutes.

The exceptional flowability of the material mix before curing allows the design and implementation of every possible shape. The polyurethane components which are liquid at room temperature are injected into the closed mold where they quickly cure to produce the finished foam.

This also contributes to the excellent cost effectiveness of polyurethane processing. The low pressures inside the mold mean it is also possible to produce polyurethane moldings in aluminum molds. The more complex the mold, the more cost-effective it is to use polyurethane.

In this instance, there was also another benefit. In addition to the chemical resistance of Baydur® 61 FR, this system also exhibits exceptional dimensional stability under changing operating temperatures. This is necessary since the comPOUND sample carrier from TTP Labtech must guarantee the same accuracy and reliability at ambient temperatures as it does down to less than –10°C.

News and information about products, applications and services from Bayer MaterialScience AG can be found at http://www.bayermaterialscience.com and information about the company’s participation in K 2004 at http://www.k2004.bayermaterialscience.com.