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Bone in general is very tough, particularly antler bone, and bird bone is very stiff, yet birds still manage to fly. The ceramic content of bird bone is extremely high. We have researched this in greater detail with a view to considering the nature of the stiffness of bone, and whether that can be mimicked using other components. We have studied the toughening mechanisms of antler bone to suggest ideas for tougher helmets and general impact protection.
In a Government funded project, we examined the potential of expanded starch in the search for the replacement of moulded polystyrene. Extruded starch has already been used as a replacement for loose fill polystyrene granules, but we aim to take the concept a stage further, and produce a starch product which can be shaped, cut or moulded, such as in the packaging materials found around most electrical goods. The benefits are obvious: the product can be recycled without difficulty, is fully biodegradable, since it would be a natural water based substance, and it could be much cheaper than the standard oil based polystyrene product.
In a series of pieces of research which have applications in the processed food industry, we have designed new methods for the analysis of crispness in the texture of food. This is mainly applicable in the areas of fruit, vegetables and cooked starch based products.
The principle of a fluid enclosed in a membrane being made to do useful work can be seen in our own muscular system, plants, and in the skin of worms. The skin of a worm is effectively a cylinder comprised of fibres that are wound in a crossed helical form around and along the worm's body. By contracting the muscles in the body wall and increasing its internal pressure the worm is able to change shape, with the fibres in the skin allowing the worm to go from short and fat to long and thin. This is the basis of a worm's locomotory mechanism. Using cylinders of various fibre angles and by replacing the worm's muscles with a polymer gel which can absorb water, we can design the swelling and contracting of the gel to do useful work. Chemical energy is converted to mechanical energy just where it is required and any pressure developed is confined to the helically-wound bag, which is intrinsically safe. Therefore, by controlling the swelling and contracting of the polymer gel, the system effectively works as an artificial muscle.
Insect sense organs
Funded by EU FP5, we have used finite element modelling to understand the design of sensors in insect cuticle. We aim to incorporate similar designs into aerospace composite materials. Preliminary results suggest that they are very sensitive detectors and permit remote interrogation for strain. Present work is concentrating on the hair-like airflow receptors found on the cerci of crickets. For further details, visit the project website (http://www.bionics-cicada.org).
We are examining plant fibres, principally flax and hemp, with a view to replacing glass fibre in low priced products, especially building materials. Glass fibre, when used in cement boards and phenolic boards, for example, cannot be recycled, nor can it be incinerated. In using plant fibres as a stiffening filler in such products, the products could then be re-used, perhaps as fuel, since they could be incinerated. The fibres can be produced by crops grown in the European Union.
By carrying out research on the opening and closing of pine cones and the insulation layers of penguins, we have worked on the principles of design of a fabric which can be used to make responsive clothing, with transpirational properties based on the state of activity of the wearer. This is of particular interest in the defence industry, meaning that the minimum of layers of clothing need be worn at all times, particularly in areas of the world with widely fluctuating temperatures: a soldier in the deserts around the Gulf will otherwise need few layers by day in the baking heat, but lots of layers by night in the chill of the sand.
The Centre for Biomimetics has created a material which uses one of the toughening mechanisms found in wood and which has in particular high resistance to impact. Now our researchers are working on a project which takes the composite one stage further, making it particularly useful in the field of protection against high velocity particles such as bullets, shrapnel from bombs or being attacked with a knife.
In another project, we are looking at the mechanical properties of wood from transgenic trees with reduced lignin content. By exploiting genetic engineering techniques, it should be possible to reduce energy consumption and pollutants from the pulp and paper industries.