The Extraordinary Design of the Bombardier Beetle: A Classic Example of Biomimetics

The innocuous looking bombardier beetle is one of the most remarkable creatures in the insect world. This tiny insect (1-1.5 cms long) is able to fight off any spider, frog, ant or bird that comes too close, by blasting the attacker with a powerful jet of hot, toxic fluid. Furthermore, the beetle can aim its weapon in any direction (even over its head) with pinpoint accuracy, and can reach distances of up to 20 cm with its spray. The bombardier beetle is rare in Europe but common in Africa, Asia and the warmer parts of the Americas, and in order to resist predators, forms a noxious spray by reacting small amounts of hydroquinone with hydrogen peroxide in a pair of combustion chambers in its abdomen, and in the presence of the catalysts catalase and peroxidase. The beetle demonstrates irreducible complexity in the following systems: 1) the sensory mechanism which gives awareness of the approach of a predator, 2) the valve system that involves both inlet and exhaust valves working synchronously, 3) the chemical production of reactants hydrogen peroxide and hydroquinone, 4) the use of catalytic chemistry to eject a controlled explosive mixture, and 5) the moveable, flexible exhaust turret to enable ejection in any direction. These and others are systems which only work when each of the component parts are operating in harmony with others in a coordinated mechanism. For chemical systems the same point applies in principle. The overall chemical system will only operate correctly if each component chemical is in place in a prepared pathway. This paper reviews the research of a number of authors (including Professor McIntosh) into the workings of the bombardier beetle spray system. Not only is this is a classic example of biomimetics (the study of design in nature and copying these designs and using them in engineering), but also tacitly underlines the necessity of design in the original beetle itself. The discovery that the McIntosh team made of sophisticated mechanisms in the beetle’s structure and chemistry demonstrates the irreducible complexity in the design of the beetle

On the use of hydrogen peroxide in ignition systems bioinspiration from the bombardier beetle

A novel ignition system was studied experimentally, in which small volumes of hydrogen peroxide -of the order of pl/s- were injected at the immediate site of ignition, during the firing of a focus discharge igniter (FDI). Initially, the new ignition system was evaluated at an atmospheric expansion rig in the Mechanical Engineering of Leeds University. Afterwards, experiments were undertaken in an atmospheric testing facility with an industrial Rolls-Royce Olympus combustion chamber using kerosene Jet-A1 as the fuel and atmospheric air as the oxidizer. The study concentrated on the determination of the lean ignition limits o f the kerosene-air mixture at various air mass flow rates with and without the addition of H20 2. Notable improvements, from 6.5% to 44%, in the ignition limits of the fuel-air mixture were attainable by using only a maximum amount o f 10.8pl/s o f H20 2 during only the ignition process. The study suggests that these improvements are directly related to the increase in the ignition efficiency of the ignitor, by radical enhancement through the injection of the H20 2 plasma medium. Comparisons were made, between a fuel atomiser that was in normal service and of the same device but washed, in order to test the igniter’s ability to initiate combustion under poor and high fuel spray qualities (FSQ). The results indicate an enhanced improvement in the ignitability limits during poor air-fuel mixing quality when using the H20 2 as described above. A biodiesel fuel was also selected to test the effect that the new ignitor system has in a low-volatility fuel. The question of how to create the small amounts of hydrogen peroxide that will be used for ignition was also approached. An idea of producing the required H20 2 came by studying the bombardier’s beetle unique mechanism which produces H20 2 for defending itself from predators. Simulation work using Chemkin was conducted to investigate the production o f H20 2 by passing hydrocarbon fuels through a catalyst. When passing propane-air through a platinum/ rhodium catalyst the simulations show that H20 2 production is possible in rates enough to supply the proposed novel ignition system. A more specialised study in the chemistry of the production of H20 2, from gas-turbine fuels, is suggested. A cost effective method o f an onsite H20 2 production in small amounts would be an ideal topic for further study