Mechano-electric

Electromagnetic earthquake forerunners show themselves like the electromagnetic phenomena, including electromagnetic emission (EME) in a radio frequency range. This emission caused by collective exiting of the set of local mechano-electrical transformers (MET). The excitation mechanism inside the crust is determined by the fact that elastic tension ranges up to the threshold level within the source area. 

Mechanosensitive ion channels can be looked at as membrane-embedded mechano-electrical switches. They play a critical role in transducing physical stresses at the cell membrane (e.g. lipid bilayer deformations) into an electrochemical response. Two types of stretch-activated channels have been reported the mechanosensitive channels of large conductance (MscL) and mechanosensitive channels of small conductance (MscS). 

The human inner ear is embedded in the temporal bone and houses the sensory epithelia of the cochlea and vestibular apparatus (Fig. 1). The sensory epithelia contain hair cells which transduce the stimulus of sound or motion into nerve impulses. Hair cells are equipped with an apical mechano-sensitive apparatus made up by three rows of actin-containing stereocilia of increasing length. Displacement of the stereocilia towards the longest row opens (gates) mechano-electrical transduction channels, whereas deflection into the opposing direction closes the channels [12],... 

Fig. 2 Design variants of hydrogel-based sensors 1 bending plate 2 mechano-electrical transducer (piezoresistive bridge) 3 swellable hydrogel 4 Si substrate (5 mm x 5 mm x 0.3 mm) 5 socket 6 tube 7 interconnect 8 solution 9 Si chip (5 mm x 5 mm x 0.4 mm). Reprinted from (Gerlach et al. 2004 Gerlach et al. 2005 Guenther et al. 2005, 2006, 2007b) with kind permission from Elsevier, Wiley-VCH and SPIE...

Chemi-opto-mechano-electricity Membrane machines.202... 

Flexoelectricity is a basic mechano-electric effect that enables the nanometre-thick membranes of living matter to function like soft machines, thus converting the electrical stimuli of the hving world into mechanical ones, and vice versa. It also allows, by using model nanomembranes, the construction of mechanosensors and actuators for nanoionics applications. 

Flexoelectricity is a basic mechano-electric phenomenon in liquid crystal physics. The first hints for the existence of a curvature-polarization tensor in liquid crystals, although with different sjmunetry transformation properties, can be foimd in a manuscript by Freedericksz (1940) that made use of the tensorial analysis method of general relativity and was published only... 

A.G. Petrov, Charge transfer processes in model and biological membranes Defect and mechano-electric aspects statics and dynamics. Mol. Cryst. Liq. Cryst. A 292(1), 227-234, (1997). doi 10.1080/10587259708031933... 

Tiwari, R. and Kim, K. J. (2010). Disc-shaped ionic polymer metal composites for use in mechano-electrical applications. Smart Materials and Structures 19, 6, p. 065016. 

Ultrasonic transducer Mechano-electrical transduction device USANS Ultra small angle neutron scattering USAXS Ultra small angle X-ray scattering UV Ultra violet... 

Stimuli-responsive polymers consist of a class of smart materials that exhibit a physical response to changes in external conditions. Such stimuli include changes in pH, ionic strength, solvent polarity, and temperature, as well as mechanical force or electric fields. On the basis of their ability to switch conformations, stimuli-responsive polymers are being applied as sensors, actuators, and transducers (e.g., mechano-electrical or mechano-optical). Nanoporous membranes can be functionalized with stimuli-responsive polymers to modify their permeability, that is, to reversibly open and close the pores upon a given stimulus. ... 

By their similitude with the receptor from living organisms these mechano-electrical systems, composed from polymer gels, open new possibilities of investigation of the artificial perception, with potential application in robotics or prosthesis. 

The teorell membrane oscillator as a mechano-electric transducer. J. Memh. Bid., 11, 197-216. 

Linear Mechano-Electrical Response Linear Electro-Mechanical Response... 

Fig. 1 Two-domain Heckmann diagram (Heckmann 1925) illustrating the linear mechano-electrical and electromechanical elfects (i.e., direct and inverse piezoelectricity, respectively) in dielectric materials. The four relevant piezoelectric coefficients d, e, g, and h are shown as horizontal or diagonal arrows in red, yellow, green, and blue, respectively, while the linear elastic and dielectric parameters arc included as vertical black arrows...

Unfortunately, even today, inverse (or converse) piezoelectricity is still sometimes called electrostriction because the name electrostriction suggests the electromechanical direction (electrical stimulus leads to mechanical response), while piezoelectricity seems to refer only to the opposite mechano-electrical direction. In order to avoid the misleading use of the term, it should be kept in mind that our modem terminology is based on phenomenological thermodynamical relations so that the linear effects of direct and inverse piezoelectricity must be identical due to the mathematically required reciprocity. 

The direct piezoelectric (or mechano-electrical) effect is due to the shear polarization arising from the distortion of the helix as illustrated in Figure 8.15. 

A. Jikli and L Bata. Mechano-electrical eflects on planar Sc liquid crystals, MoL Cryst Uq. Cryst 201 115 (1991). 

Belhora, F., Cottinet, P.J., Hajjaji, A., Guyomar, D., Mazroui, M., Lebrun, L., Boughaleb, Y., 2013. Mechano-electrical conversion for harvesting energy with hybridization of electro-strictive polymers and electrets. Sensors and Acmators A 201, 58—65. 

In the next section, an overview of the main biomedical tpplications based on shape-changing materials in response to natural stimulus (temperature—thermoresponsive materials, pH— pH-responsive materials, and mechanical—mechano-electrical materials) will be presented. 

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