Characterizations of the reaction chambers of bombardier beetles

Pao Yue-kong Library Electronic Theses Database

Characterizations of the reaction chambers of bombardier beetles

 

Author: Guo, Zhenbin
Title: Characterizations of the reaction chambers of bombardier beetles
Degree: M.Sc.
Year: 2016
Subject: Bombardier beetles -- Defenses.
Hong Kong Polytechnic University -- Dissertations
Department: Faculty of Engineering
Pages: xi, 84 pages : color illustrations
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2917025
URI: http://theses.lib.polyu.edu.hk/handle/200/8600
Abstract: The defense mechanism of the bombardier beetle is most unusual in that an aqueous combustible mixture of hydroquinone and hydrogen peroxide is catalysed by catalase and peroxidase which then heats the solution to boiling point. Evaporation then occurs within a few milliseconds and the mixture is ejected at 100°C on predators using a variable angle outlet nozzle which can be directed for pinpoint accuracy. This thesis will mainly focus on the thermal properties and mechanical properties of the reaction chamber which is the key component to the bombardier beetles' defense system. By conducting the thermal properties testing experiment in this thesis, we could convince that the RCs possess a good thermal insulation property. Then a theoretical model was developed to illustrate the thermal properties of reaction chambers. The experimental data together with the simulation results shows that the RCs are a thermal isolation material. In this thesis, a primary study on the mechanical properties of RCs was given from the laminate basal part and the hair-like fibers inside reaction chamber. The outer layer of reaction chamber possesses better mechanical properties than the inner layer from our result: the difference of storage modulus and hardness could up to several times. The mechanical properties of the hair-like fibers are ductile which could endure high deformation up to 40% strain before fractured. Moreover, those fibers also presented its high toughness to us by the brittle-like fracture mode under deformation. So we could believe that the haired wall will absorb and store energy under the pulse reaction. For the material analysis of the material's information of RCs, the TGA analysis shows that the total organic content of the RCs is 86 wt% and the inorganic content of the RCs is less than 2 wt%. Combining to the XRD and EDX analysis on the reaction chambers, there are some crystallized Chitin and calcium element presented in RCs.

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