In the past ten years, biological piezoelectric materials have emerged as the potential next generation
of cost-effective, green electromechanical sensors1, 2. The piezoelectric voltages produced under an
applied force are inversely proportional to the dielectric constant of the material and so even ‘weak’
organic piezoelectrics (with modest piezoelectric constants compared to inorganic ceramics3, 4), can
generate large voltages in response to strain. Amino acids are the simplest biological units, and are
inexpensive and easy to crystallise5-7, and demonstrate measurable piezoelectricity in single crystal8-10
and polycrystalline forms11, 12
.
Recently we have experimentally validated flexible glycine-based sensors for pipe leak detection and
monitoring in real-time, for a variety of flow rates and leak sizes using a custom fluid test rig developed
for the validation of PVDF patches13. This is the first time that glycine crystals have been grown and
characterised as a high-concentration, polycrystalline aggregate for piezoelectric sensing14. However a
key limitation of this study is that the piezoelectric response of the film was less than that of glycine
single crystals due to the random orientation of glycine crystallites11
.
In this work, we will systematically study the effect of crystallisation growth parameters on a number
of polycrystalline amino acid films in order to modulate the piezoelectric response and increase the
detection sensitivity and voltage output of amino acid-based piezoelectric devices. Moreover, we will
investigate and optimise different parameters involved in the polycrystalline film growth and
characterise the formed polycrystalline films using Scanning Electron Microscopy, X-Ray Diffraction,
and Scanning Probing Microscopy. The study will highlight the potential of low-dielectric, noncentrosymmetric biomolecular crystal films for widespread monitoring of built infra-structure systems
by showing how reliably and sustainably they may be used as sensors for pipe structural health
monitoring (SHM) applications.