Chiang Mai Journal of Science

Paper Type 

Title 

Author 

Email 

Smart materials function as both sensors and actuators. This combination of sensing and actuating mimics two of the functions of a living system ñ namely, being aware of the surroundings and being able to respond to that signal with a useful response, often in the form of a motion. Smart materials sometimes have a control system and sometimes not. Four major families of actively smart materials have emerged during the past few years: piezoelectric and electrostrictive ceramics typified by Pb(Zr,Ti)O₃ and Pb(Mg,Nb)O₃ , usually referred to as PZT and PMN, and magnetostrictive and shape-memory alloys such as terfenol (Tb,Dy)Fe₂ and nitinol, NiTi. All four materials are primary ferroics (ferroelectric, ferromagnetic, or ferroelastic) with domain-wall motions that assist in the sensing and actuating functions. Two phase transformations are involved in most of these smart materials. Another approach to making smart materials is to bring together two or more different materials, each of which has a phase transition or an instability associated with it. In our transducer program, we combine polymers or metals operating near an elastic or mechanical instability with ferroelectric ceramics in which the dielectric properties undergo a transition. The two materials have different types of instability, enabling us to build up structures especially tuned for sensing and actuating. These functional composite materials take advantage of the fact that when optimizing a smart material, generally one is not trying to optimize all the electromechanical coupling coefficients, but only those tensor coefficients appearing in the figure of merit of the device. Taking advantage of the mixing rules, we build series and parallel connectivity patterns into the composites using electrically soft ferroelectric phase and a mechanically soft polymer. A variety of  transducer materials with large electromechanical coupling coefficients have been constructed in this way. The composite transducers illustrate a very general approach that applies not only to piezoelectric materials but to many other functional composites.

Start & End Page 

Received Date 

Revised Date 

Accepted Date 

Full Text 

Keyword 

Volume 

DOI 

SDGs