Hyperspectral interference tomography of nacre.

Area of Science:

• Materials Science
• Biomineralization
• Optical Physics

Background:

• Structural characterization of biomaterials like nacre is crucial for understanding biological processes and developing bio-inspired materials.
• Nacre's strength and optical properties stem from its nanoscale "brick-and-mortar" structure of aragonite tablets and organic layers.
• Current characterization methods are destructive, time-consuming, and limit analysis to small sample areas.

Purpose of the Study:

• To introduce a novel, all-optical, rapid, and nondestructive imaging technique for characterizing disordered layered materials.
• To spatially map structural parameters of nacre across large areas of mollusk shells.
• To investigate the relationship between nacre structure and mollusk age.

Main Methods:

• Developed hyperspectral interference tomography (HIT), combining hyperspectral imaging with optical-interference modeling.
• Applied HIT to analyze nacre from red (Haliotis rufescens) and rainbow (Haliotis iris) abalone shells.
• Inferred mean tablet thickness and its disorder non-destructively across entire shells.

Main Results:

• Successfully mapped nacre structural parameters over large sample areas using the nondestructive HIT technique.
• Observed an unexpected decrease in nacre tablet thickness with increasing age in red abalone.
• Demonstrated the potential for in-field application due to the method's speed and low cost.

Conclusions:

• Hyperspectral interference tomography (HIT) offers a rapid, inexpensive, and nondestructive alternative for structural characterization of nacre and similar materials.
• The study reveals a novel developmental trend in nacre structure, with tablet thickness decreasing over time in red abalone.
• This technique has broad applicability for in-field studies of biomaterials and environmental monitoring.