Bioelectromechanical imaging by scanning probe microscopy: Galvani's experiment at the nanoscale

Abstract

Since the discovery in the late 18th century of electrically induced mechanical response in muscle tissue, coupling between electrical and mechanical phenomena has been shown to be a near-universal feature of biological systems. Here, we employ scanning probe microscopy (SPM) to measure the sub-Angstrom mechanical response of a biological system induced by an electric bias applied to a conductive SPM tip. Visualization of the spiral shape and orientation of protein fibrils with 5 nm spatial resolution in a human tooth and chitin molecular bundle orientation in a butterfly wing is demonstrated. In particular, the applicability of SPM-based techniques for the determination of molecular orientation is discussed.

Ferroelectric or non-ferroelectric: Why so many materials exhibit “ferroelectricity” on the nanoscale

“…These behaviors often average out in macroscopic biological assemblies, since the piezoelectric effect is described by third rank tensor. However, on the nanoscale these polar regions are readily visualized by PFM, providing spectacular images of bones, 141 antlers 142 teeth, [143][144][145][146][147] and even butterfly wings. 147 Several examples are shown in Figure 4.…”

Dynamic behaviour in piezoresponse force microscopy

“…(15)(16)(17)(18), all four contributions decrease with frequency due to the dynamic stiffening effects. Even in the absence of damping, the non-local contribution scales as a higher power of frequency, suggesting that non-local cantilever effects will be minimized at high frequencies.…”

Preface to Special Topic: Selected Papers from the Piezoresponse Force Microscopy Workshop Series: Part of the Joint ISAF-ECAPD-PFM 2012 Conference

“…58 Furthermore, the 2010 Preface also predicted opportunities for new discoveries and breakthroughs in biological systems and strongly correlated oxides, and one of the exciting developments in the last two years is the observation of biological ferroelectricity in seashells, 22 aortic walls, 23 elastin, 24 glycine, 25 and peptide nanotubes, 26 which came more than 50 years after the closely related piezoelectricity was reported in biological tissues and 5 years after ubiquitous presence of biological piezoelectricity was established by PFM. [27][28][29][30][31] This advance is undoubtedly enabled by PFM, as vividly illustrated by Li and Zeng in their detailed studies on electromechanical coupling and ferroelectric switching of seashell in the present issue. 59 Another exciting development is recent realization of polarization reversal by mechanical stress, 32 attributed to the flexoelectric effect afforded by nanoscale Scanning Probe Microscopy (SPM) tip.…”