Submillimetre mechanistic designs of termite-built structures

Area of Science:

• Materials Science
• Bioengineering
• Architecture

Background:

• Termite mounds serve multiple functions: nurseries, food storage, and microclimate regulation.
• Previous research focused on termite building behavior, not the mound's material composition.
• Understanding mound architecture is crucial before analyzing how multi-functionality shapes termite construction.

Purpose of the Study:

• To investigate the submillimeter mechanistic architecture of *Nasutitermes exitiosus* mounds.
• To identify the material components and structural properties of termite mounds.
• To explore the potential of termite mound structures for bio-inspired material design.

Main Methods:

• Granulometry and Fourier transform infrared spectroscopy (FTIR) for particle size and composition analysis.
• High-resolution micro-computed X-ray tomography (micro-CT) for 3D structural imaging.
• Microindentation tests to determine mechanical properties and material moduli.

Main Results:

• Identified preferential particle sizes (coarse silts) and unknown organic/inorganic mixtures.
• Revealed filigree laminated wall layers with sub-millimeter porosity around a coarse-grained scaffold.
• Scaffold geometry resembles trabecular bone, composed of lignin-based composite and biocementitious stercoral mortar.
• Multi-scaled porosity confirmed via fractal dimension estimates, aiding evaporative cooling and stability.
• Indentation moduli increased towards the inner wall, exceeding loose clays and some cementitious materials.

Conclusions:

• Termites engineer intricate, layered biocementitious composites with high elasticity.
• The multi-scaled porosity and structural integrity offer insights into bio-architected lightweight, high-strength materials.
• Termite mound structures present a novel paradigm for developing advanced engineered materials.