Keynote Talk 

Piezoelectric biomaterials are being considered for numerous sensing, nanoelectronics, and tissue engineering applications. At the same time, biomedical applications of inorganic piezo- and ferroelectric materials continue to grow. Progress in investigating and exploiting the piezoelectric properties and surface charge of these functional materials will be presented, with a focus on understanding the origin and role of piezoelectricity in type I collagen using piezoresponse force microscopy (PFM). Specifically, the role moisture content and crosslinking on electromechanical coupling in type I collagen will be presented.

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Type I collagen piezoelectricity, as determined by PFM, was found to persist at high (> 60%) relative humidity (Figure 1). The piezoresponse was highest at intermediate values of relative humidity, suggestive of a role of water on the measured signal. It was also found that non-enzymatic crosslinking, which may have implications for understanding the functional changes of collagen, e.g., during aging, led to reduced piezoelectricity; crosslinked samples showed improved stability in collagenase, supporting that crosslinking took place.

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Additionally, aligned collagen films prepared with different fibril sizes have been investigated to explore whether the characteristic ‘piezoelectric domain’ size of the films can be controlled in a deterministic way. Engineered collagen films with aligned fibrils and uniform polarization might be useful in, e.g., energy harvesting and tissue engineering applications. The interaction of such piezoelectric domains (and ferroelectric domains in the case of lithium niobate surfaces) with cell migration and the influence of topographic cues are explored.

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Figure 1: Topography (left), PFM amplitude (middle), and PFM phase (right) images of tendon collagen recorded under different relative humidity values.

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