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Journal of the mechanical behavior of biomedical materials
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Item-typ:Veröffentlichung, Dynamic mechanical analysis reveals reversible thermal effects in insect tibial cuticleThe mechanical performance of insect cuticle arises from its composite structure of chitin fibres embedded in a protein-rich matrix. While chitin contributes to thermal resistance and structural integrity, the protein component is temperature-sensitive and modulates viscoelastic behaviour. Here, we investigated how thermal exposure affects the mechanical properties of tibial cuticle in Locusta migratoria, using dynamic mechanical analysis (DMA) across a temperature range (22–74 °C) and following prior heating to 60 °C or 70 °C. Both storage and loss moduli decreased significantly with increasing temperature by approx. 64 %, respectively 42 %, consistent with partially reversible thermal softening. After re-cooling, the loss modulus increased again to control levels, whereas the storage modulus remained significantly reduced. Tan δ increased significantly with increasing temperature by approx. 31 % and remained higher in pre-heated samples, reflecting a shift toward more compliant and dissipative behaviour. No significant differences were detected between the 60 °C and 70 °C treatments. These results suggest that thermal exposure induces reversible changes in matrix protein mobility and non-covalent interactions, affecting stiffness more strongly than damping. The cuticle thus exhibits partial recovery of mechanical function after heating, which may reflect an adaptive response to transient thermal stress.Wissenschaftlicher ArtikelBand:1798 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, The role of the membrane in the hen's egg as a model for increasing the toughness of engineered brittle materialsEggshell and the attached membrane are the focus of many fields of research, but their mechanical properties as a biomineralised composite are seldom explored. This investigation aimed to asses the influence of the membrane on energy dissipation during macroscopic structure failure, and if this effect could be reproduced with artificial membranes for later use in biomimetic materials. Compression tests followed by fracture pattern analysis were conducted for five types of manipulated egg halves: samples with and without the natural membrane, and three samples where the membrane was replaced with artificial membranes made from epoxy resin, polyurethane resin, or wood glue. To preserve the shell's shape, the natural membrane was removed with NaClO. Significant differences regarding the fracture forces between samples with the natural membrane and no membrane (20 % decrease of average), and the natural and artificial membranes (30 % increase of average) were measured. Fracture pattern analysis and investigation of the total work performed during compression testing revealed the highest improvements in toughness for the artificial polyurethane-resin membrane. Without any membrane, very small amounts of work were required to completely shatter the egg, and no fragment cohesion was observed. The presence of the membrane significantly enhanced the effective toughness of the eggshell, and the biomimetic abstraction of this concept is considered feasible for further investigation involving engineered brittle materials.Wissenschaftlicher ArtikelBand:17011 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, A dermal light sensor controls anisotropic biomechanical properties in insect cuticleThe cuticle of many insects shows the presence daily growth bands, consisting of alternating layers of parallel chitin fibres deposited during the day and helicoidal fibres deposited at night. In locusts this rhythmic deposition is controlled by a circadian mechanism linked to a local epidermal light sensor. So far, it is not understood if this light sensitivity leads to any biomechanical advantages. It is here hypothesized that the light sensor may act as an external trigger, using consistent environmental stimuli to regulate the fibre deposition process. This regulation could serve to override the self-organized helicoidal arrangement and prevent the accumulation of irregularities at the cellular level during cuticle formation. Based on established principles of fibre-reinforced composite materials, the presence of regular cuticular growth bands likely influences the biomechanical properties of the cuticle, particularly its anisotropic response to mechanical stresses such as tension and compression. This study employs a combined approach of simulated chitin-fibre deposition and standardized finite element modeling to demonstrate that an external trigger can play an important role in controlling the anisotropic biomechanical properties of insect cuticle.Wissenschaftlicher ArtikelBand:16937