Biological Ferroelectricity Uncovered in Aortic Walls by Piezoresponse Force Microscopy

Abstract

Many biological tissues are piezoelectric and pyroelectric with spontaneous polarization. Ferroelectricity, however, has not been reported in soft biological tissues yet. Using piezoresponse force microscopy, we discover that the porcine aortic walls are not only piezoelectric, but also ferroelectric, with the piezoelectric coefficient in the order of 1 pm/V and coercive voltage approximately 10 V. Through detailed switching spectroscopy mapping and relaxation studies, we also find that the polarization of the aortic walls is internally biased outward, and the inward polarization switched by a negative voltage is unstable, reversing spontaneously to the more stable outward orientation shortly after the switching voltage is removed. The discovery of ferroelectricity in soft biological tissues adds an important dimension to their biophysical properties, and could have physiological implications as well.

Research on bioelectromechanics for 70 years

“…In this case, the polarity of each collagen crystals is kept even partly in the same direction of orientation. For this symmetry, seven piezoelectric constants are available, d 14 31 , and d 33 . In addition to the shear piezoelectricity, the tensile piezoelectricity is observed for bone and tendon.…”

“…In 2012, Dr. J.Li in the University of Seattle published a paper on the piezoelectricity and ferroelectricity of aorta walls observed by PFM [33]. The elongation of sample and putting electrodes are not necessary.…”

The renaissance of continuum mechanics

“…Growth and remodeling are two particular phenomena associated with biological materials, which require special treatments in constitutive modeling (Skalak et al, 1982;Taber, 1995;Cowin, 2004); 3. Multiple fields (e.g., mechanical, chemical, thermal, electrical, and physiological) coexist and may couple together (Fukada, 1968;Liu et al, 2012;Wilson et al, 2013).…”

Coplanar switching of polarization in thin films of vinylidene fluoride oligomers

“…[1][2][3] Recent reports feature such materials as donor-acceptor charge transfer complexes, 4,5 supramolecular-assemblies, 6 polar structures with relatively high melting temperature, 2,7 metal-organic coordination compounds, 8,9 and biological tissues. 10,11 These research efforts are focused on uncovering the fundamental mechanisms of molecular ferroelectricity and phase transformations, as well as on designing novel ferroelectric materials for application in electronic devices. Vinylidene fluoride (VDF) based ferroelectrics and their trifluoroethylene (TrFE) copolymers are the most widely studied organic ferroelectrics and used, primarily because of their relatively high polarization value (approximately 10 lC/cm 2 ), biocompatibility, non-toxicity, and ease of large scale fabrication by low cost solvent-based methods.…”