Designing soft pyroelectric and electrocaloric materials using electrets

Darbaniyan, Faezeh; Dayal, Kaushik; Liu, Liping; Sharma, Pradeep

doi:10.1039/c8sm02003e

Cited by 20 publications

(10 citation statements)

References 47 publications

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“…[ 36 ] Recent theoretical modeling has well‐explained the origins of the apparent piezoelectric, flexoelectric, and pyroelectric behavior in electrets (in otherwise nonpiezoelectric) materials due to the interaction of Maxwell stress (or electrostriction), deformation nonlinearity, and the presence of the charges or dipoles. [ 37–41 ]…”

Section: Figurementioning

confidence: 99%

2D Electrets of Ultrathin MoO₂ with Apparent Piezoelectricity

et al. 2020

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Since graphene, a variety of 2D materials have been fabricated in a quest for a tantalizing combination of properties and desired physiochemical behavior. 2D materials that are piezoelectric, i.e., that allow for a facile conversion of electrical energy into mechanical and vice versa, offer applications for sensors, actuators, energy harvesting, stretchable and flexible electronics, and energy storage, among others. Unfortunately, materials must satisfy stringent symmetry requirements to be classified as piezoelectric. Here, 2D ultrathin single‐crystal molybdenum oxide (MoO2) flakes that exhibit unexpected piezoelectric‐like response are fabricated, as MoO2 is centrosymmetric and should not exhibit intrinsic piezoelectricity. However, it is demonstrated that the apparent piezoelectricity in 2D MoO2 emerges from an electret‐like behavior induced by the trapping and stabilization of charges around defects in the material. Arguably, the material represents the first 2D electret material and suggests a route to artificially engineer piezoelectricity in 2D crystals. Specifically, it is found that the maximum out‐of‐plane piezoresponse is 0.56 pm V−1, which is as strong as that observed in conventional 2D piezoelectric materials. The charges are found to be highly stable at room temperature with a trapping energy barrier of ≈2 eV.

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Section: Figurementioning

confidence: 99%

2D Electrets of Ultrathin MoO₂ with Apparent Piezoelectricity

et al. 2020

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“…as this could correspond to a bending about some axis in thê e1,ê2 plane. In this case, [27] such that, in general, we have a nonzero polarization. Further, we can see from Eq.…”

Section: Flexoelectricity and The Elastomer Unit Cellmentioning

confidence: 99%

“…Upon a closer examination, we notice that the third term is exactly the flexoelectricity constant we obtained in Eq. (27) for the case K1 = K2 = K3 = K4 = 1, which is equivalent to the electrically isotropic case.…”

Section: The Design Of Elastomers For Emergent Flexoelectricitymentioning

confidence: 99%

Flexoelectricity in soft elastomers and the molecular mechanisms underpinning the design and emergence of giant flexoelectricity

Grasinger

Mozaffari

Sharma

2021

Proc. Natl. Acad. Sci. U.S.A.

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Soft robotics requires materials that are capable of large deformation and amenable to actuation with external stimuli such as electric fields. Energy harvesting, biomedical devices, flexible electronics, and sensors are some other applications enabled by electroactive soft materials. The phenomenon of flexoelectricity is an enticing alternative that refers to the development of electric polarization in dielectrics when subjected to strain gradients. In particular, flexoelectricity offers a direct linear coupling between a highly desirable deformation mode (flexure) and electric stimulus. Unfortunately, barring some exceptions, the flexoelectric effect is quite weak and rather substantial bending curvatures are required for an appreciable electromechanical response. Most experiments in the literature appear to confirm modest flexoelectricity in polymers although perplexingly, a singular work has measured a “giant” effect in elastomers under some specific conditions. Due to the lack of an understanding of the microscopic underpinnings of flexoelectricity in elastomers and a commensurate theory, it is not currently possible to either explain the contradictory experimental results on elastomers or pursue avenues for possible design of large flexoelectricity. In this work, we present a statistical-mechanics theory for the emergent flexoelectricity of elastomers consisting of polar monomers. The theory is shown to be valid in broad generality and leads to key insights regarding both giant flexoelectricity and material design. In particular, the theory shows that, in standard elastomer networks, combining stretching and bending is a mechanism for obtaining giant flexoelectricity, which also explains the aforementioned, surprising experimental discovery.

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“…So far, numerous works have been documented to shed light on the material preparation, the charge retention capacity, and the expending application scale of those available polymer counterparts 20–22 . For example, experiments reveal that the inflation would tune the electromechanical property of cellular piezo‐electret films, particularly in the thickness direction 23 .…”

Section: Introductionmentioning

confidence: 99%

Polymer electrets and their applications

Wang

et al. 2020

J of Applied Polymer Sci

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Polymer electrets have revealed great potential application in electromechanical devices because of the low weight, large quasi‐piezoelectric sensitivity, and excellent flexibility. For an electret, a permanent and macroscopic electric field exists on the surface, principally led by a macroscopic electrostatic charge on the surface or a net orientation of polar groups inside the object. Here, progress in the development of polymer electrets is reviewed. After a brief retrospect of the research courses and those typical polymer electrets that are classified into fluorine polymer and nonfluorine polymer, we present a survey on the charging methods, including corona, soft X‐ray, contact, thermal and monoenergetic particle beams. The latest representative applications (i.e., power harvesting, sensors, field effect transistors, and biomedicine) based on polymer electrets are also summarized. Finally, we complete this review with a discussion on perspectives and challenges in this field.

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Designing soft pyroelectric and electrocaloric materials using electrets

Abstract: A temperature variation can electrically polarize a pyroelectric material.

Cited by 20 publications

References 47 publications

2D Electrets of Ultrathin MoO₂ with Apparent Piezoelectricity

2D Electrets of Ultrathin MoO₂ with Apparent Piezoelectricity

Flexoelectricity in soft elastomers and the molecular mechanisms underpinning the design and emergence of giant flexoelectricity

Polymer electrets and their applications

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Designing soft pyroelectric and electrocaloric materials using electrets

Abstract: A temperature variation can electrically polarize a pyroelectric material.

Cited by 20 publications

References 47 publications

2D Electrets of Ultrathin MoO2 with Apparent Piezoelectricity

2D Electrets of Ultrathin MoO2 with Apparent Piezoelectricity

Flexoelectricity in soft elastomers and the molecular mechanisms underpinning the design and emergence of giant flexoelectricity

Polymer electrets and their applications

Contact Info

Product

Resources

About

2D Electrets of Ultrathin MoO₂ with Apparent Piezoelectricity

2D Electrets of Ultrathin MoO₂ with Apparent Piezoelectricity