Further biomimetic challenges from the bombardier beetle: The intricate chemical production system

Abstract

Since the important work by Eisner showing the nature of the bombardier beetle pulse ejection system, a considerable number of biomimetic advantages have been gained by mimicking the unique spray system based on the unique coordinated inlet and outlet valve system that the beetle has. This paper discusses the equally remarkable production by the bombardier beetle of hydroquinone and hydrogen peroxide, followed by the catalytic combustion of these reactants and subsequent heating of the water diluent and the emergence of the hot caustic spray through a nozzle that can be turned in any direction. This paper considers the possible chemical mechanisms for the production of hydrogen peroxide within the narrow tube. The current production of peroxide is usually by a batch chemical autoxidation process involving a number of stages of which the two main ones are firstly a hydrogenation reaction of anthroquinone over Ni or Pd catalysts producing anthroquinol, then secondly followed by an oxidiser reaction where the anthroquinol is turned back to anthroquinone and hydrogen peroxide. This method involves considerable energy expended in heating and cooling at each stage and condensing out the peroxide from the water - H2O2 mixture at the end of the process. The bombardier beetle is able to produce the peroxide at room temperature with little energy loss in the system. Although there are some similarities to the current industrial method, the benefits of mimicking the beetle system are obviously very beneficial in terms of the greatly increased efficiency of peroxide production. © 2010 WIT Press.