# Water-Processable Intercalated Graphitic Pyroproteins and Electromechanic Properties for Smart Structural Bricks

## TL;DR

Researchers developed a new type of smart brick using a material made from silk and clay, which can sense structural changes and has potential for use in construction.

## Contribution

A novel synthesis method for phosphate-intercalated graphitic pyroprotein (P-GPy) from silk fibroin and its integration into smart bricks.

## Key findings

- P-GPy was successfully synthesized from silk fibroin using a regeneration process and thermal treatment.
- P-GPy composites in clay exhibit piezo-impedance and piezoresistive properties suitable for strain sensing.
- The material can be exfoliated in water into layered graphene sheets with uniform phosphate distribution.

## Abstract

This study introduces
a novel method for synthesizing
phosphate-intercalated
graphitic pyroprotein (P-GPy) using the regeneration process of silk
fibroin (SF). SF was prepared by mixing degummed silk fibers and calcium
chloride (CaCl2) in formic acid, resulting in a silk I-like
conformation, which was then converted into silk II by being redissolved
in phosphate buffer (PBS). We find that the β-sheet structure
of silk II is transformed to an sp2-hybridized carbon structure
by simple heating. Techniques such as Raman, XRD, and SEM with EDS
mapping demonstrate successful creation of P-GPy characterized by
a uniform phosphate distribution. We demonstrate the exfoliation in
water of P-GPy in layered graphene sheets. SF dissolved in PBS was
added to clay, and the thermal treatment required for firing the refractory
bricks is used to obtain P-GPy. Electrical impedance spectroscopy
was employed to investigate the piezo-impedance and piezoresistive
behaviors of clay-based P-GPy composites, demonstrating the potential
of the fabricated bricks to function as smart strain sensors for structural
health monitoring.