Robotic Materials

14 results (View BibTeX file of all listed publications)

2022

Simulating Electrohydraulic Soft Actuator Assemblies Via Reduced Order Modeling
Simulating Electrohydraulic Soft Actuator Assemblies Via Reduced Order Modeling

Hainsworth, T., Schmidt, I., Sundaram, V., Whiting, G. L., Keplinger, C., MacCurdy, R.

SOFT ROBOTICS. IEEE INTERNATIONAL CONFERENCE. 5TH 2022. (RoboSoft 2022), pages: 21-28, Institute of Electrical and Electronics Engineers (IEEE), 2022 IEEE 5th International Conference on Soft Robotics (RoboSoft), April 2022 (conference)

Abstract
Soft robots compliment traditional rigid robots by expanding their capabilities to interact with the physical world. A robot made with compliant, soft materials can benefit from their inherent continuum mechanics to achieve interactions with the environment that a rigid robot may find difficult. This can include grasping delicate objects, navigating through variable terrain, or working alongside humans in a safer manner. The flexible, adaptable nature of soft robots provide these benefits, but they also make predicting their actuated response a difficult, computationally-intensive task. Here we provide a non-linear, reduced order model informed by collected data on hydraulically amplified self-healing electrostatic actuators (HASELs). With this reduced order model, we simulate robots comprised of multiple actuators in an effort to rapidly evaluate potential design candidates without the need for time-consuming manufacturing. The simulation leverages a reduced-order model of HASELs based on a parallel mass spring damper (MSD) representation, made of two non-linear springs, and a damper; this data-driven parameter identification aids model fidelity. We construct a robotic manipulator actuated via six HASELs and show that the simulations driven by the non-linear MSD models accurately predict the robot's physical behavior on a macro scale. While this work focuses on a specific actuator type, the approach shown here could be extended to other linearly expanding soft actuators. Using this method, soft robotic assemblies actuated via HASELs can be rapidly evaluated in simulation before a laborious manufacturing process, which in turn will allow for faster design iterations to create more effective robots.

link (url) DOI [BibTex]

2022

Hainsworth, T., Schmidt, I., Sundaram, V., Whiting, G. L., Keplinger, C., MacCurdy, R. Simulating Electrohydraulic Soft Actuator Assemblies Via Reduced Order Modeling SOFT ROBOTICS. IEEE INTERNATIONAL CONFERENCE. 5TH 2022. (RoboSoft 2022), pages: 21-28, Institute of Electrical and Electronics Engineers (IEEE), 2022 IEEE 5th International Conference on Soft Robotics (RoboSoft), April 2022 (conference)

link (url) DOI [BibTex]

2021

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Electriflow: Augmenting Books With Tangible Animation Using Soft Electrohydraulic Actuators

Purnendu, , Novack, S., Acome, E., Alistar, M., Keplinger, C., Gross, M. D., Bruns, C., Leithinger, D.

In SIGGRAPH ’21: ACM SIGGRAPH 2021 Labs, pages: 8, ACM, New York, NY, Special Interest Group on Computer Graphics and Interactive Techniques Conference (SIGGRAPH 2021), July 2021 (inproceedings)

Abstract
We present Electriflow: a method of augmenting books with tangible animation employing soft electrohydraulic actuators. These actuators are compact, silent and fast in operation, and can be fabricated with commodity materials. They generate an immediate hydraulic force upon electrostatic activation without an external fluid supply source, enabling a simple and self-contained design. Electriflow actuators produce an immediate shape transition from flat to folded state which enabled their seamless integration into books. For the Emerging Technologies exhibit, we will demonstrate the prototype of a book augmented with the capability of tangible animation.

link (url) DOI [BibTex]

2021

Purnendu, , Novack, S., Acome, E., Alistar, M., Keplinger, C., Gross, M. D., Bruns, C., Leithinger, D. Electriflow: Augmenting Books With Tangible Animation Using Soft Electrohydraulic Actuators In SIGGRAPH ’21: ACM SIGGRAPH 2021 Labs, pages: 8, ACM, New York, NY, Special Interest Group on Computer Graphics and Interactive Techniques Conference (SIGGRAPH 2021), July 2021 (inproceedings)

link (url) DOI [BibTex]

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Electriflow: Soft Electrohydraulic Building Blocks for Prototyping Shape-changing Interfaces

Purnendu, , Novack, S. M., Acome, E., Keplinger, C., Alistar, M., Gross, M. D., Bruns, C., Leithinger, D.

In DIS ’21: Designing Interactive Systems Conference 2021, pages: 1280-1290, ACM, New York, NY, Designing Interactive Systems Conference (DIS 2021), June 2021 (inproceedings)

Abstract
We present Electriflow: a new class of soft electrohydraulic actuators as building blocks for prototyping shape-changing interfaces. These actuators are silent and fast in operation and can be fabricated with commodity materials. Electriflow generates an immediate hydraulic force upon electrostatic activation without an external fluid supply source, enabling a simple and compact self-contained design. This paper describes the materials and mechanisms of these shape-changing building blocks, as well as the underlying fabrication process, which includes a software tool that assists in their design, shape visualization and construction. Finally, we explore four classes of application prototypes: tangible animation, actuating origami creases, shape-changing phone, and shape-changing bowl.

link (url) DOI [BibTex]

Purnendu, , Novack, S. M., Acome, E., Keplinger, C., Alistar, M., Gross, M. D., Bruns, C., Leithinger, D. Electriflow: Soft Electrohydraulic Building Blocks for Prototyping Shape-changing Interfaces In DIS ’21: Designing Interactive Systems Conference 2021, pages: 1280-1290, ACM, New York, NY, Designing Interactive Systems Conference (DIS 2021), June 2021 (inproceedings)

link (url) DOI [BibTex]

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Soft Electrohydraulic Actuators for Origami Inspired Shape-Changing Interfaces

Purnendu, , Acome, E., Keplinger, C., Gross, M. D., Bruns, C., Leithinger, D.

In CHI EA ’21: Extended Abstracts of the 2021 CHI Conference on Human Factors in Computing Systems, pages: 377, ACM, New York, NY, Conference on Human Factors in Computing Systems (CHI 2021), May 2021 (inproceedings)

Abstract
In this paper, we present electrohydraulic actuators for origami inspired shape-changing interfaces, which are capable of producing sharp hinge-like bends. These compliant actuators generate an immediate hydraulic force upon electrostatic activation without an external fluid supply source, are silent and fast in operation, and can be fabricated with commodity materials. We experimentally investigate the characteristics of these actuators and present application scenarios for actuating existing objects as well as origami folds. In addition, we present a software tool for the design and fabrication of shape-changing interfaces using these electrohydraulic actuators. We also discuss how this work opens avenues for other possible applications in Human Computer Interaction (HCI).

link (url) DOI [BibTex]

Purnendu, , Acome, E., Keplinger, C., Gross, M. D., Bruns, C., Leithinger, D. Soft Electrohydraulic Actuators for Origami Inspired Shape-Changing Interfaces In CHI EA ’21: Extended Abstracts of the 2021 CHI Conference on Human Factors in Computing Systems, pages: 377, ACM, New York, NY, Conference on Human Factors in Computing Systems (CHI 2021), May 2021 (inproceedings)

link (url) DOI [BibTex]

2019

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Area-of-effect softbots (aoes) for asteroid proximity operations

McMahon, J., Mitchell, S. K., Oguri, K., Kellaris, N., Kuettel, D., Keplinger, C., Bercovici, B.

In 2019 IEEE Aerospace Conference (AERO 2019), pages: 1554-1569, IEEE, Piscataway, NJ, IEEE Aerospace Conference (AERO 2019), 2019 (inproceedings)

Abstract
This paper will provide an introduction and overview of Area-of-Effect Softbots (AoES), which are currently in development under a Phase 2 NASA Innovative Advanced Concepts (NIAC) project. AoES are designed to operate in proximity to, and on the surface of, small asteroids to support mining and planetary defense missions. Their unique design and capabilities are dependent on the incorporation of soft, compliant, and lightweight materials. AoES have a large area-to-mass ratio which allows them to take advantage of the peculiarities of the dynamical environment around small asteroids. Specifically, AoES will use solar radiation pressure to sail to the surface of the target asteroid after being deployed at a safe altitude from a mothership around the asteroid. This capability and the associated control laws will be demonstrated, removing the need for propulsion systems. Furthermore, the large, flexible surface area allows for robustness with respect to uncertainty about the asteroid surface structure - it can provide flotation to prevent sinking into a very loose, dusty regolith, and also provide anchoring to the surface through natural and electroadhesion forces. The enabling technology that will allow the AoES design loop to close is a new class of soft actuators known as HASEL actuators. These actuators harness an electrohydraulic mechanism, whereby electrostatic forces generate hydraulic pressure to drive shape change in a soft fluidfilled structure. HASELs provide an extremely power- and mass-efficient mechanism for actuating the large flexible surface areas that are the essential components defining AoES. Current system design, requirements, and key tradeoffs will be discussed - with a particular focus on the actuation, mobility, anchoring, materials, and power systems/components. The nominal mission profile and concept of operations for using

link (url) DOI [BibTex]

2019

McMahon, J., Mitchell, S. K., Oguri, K., Kellaris, N., Kuettel, D., Keplinger, C., Bercovici, B. Area-of-effect softbots (aoes) for asteroid proximity operations In 2019 IEEE Aerospace Conference (AERO 2019), pages: 1554-1569, IEEE, Piscataway, NJ, IEEE Aerospace Conference (AERO 2019), 2019 (inproceedings)

link (url) DOI [BibTex]

2018

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System identification and closed-loop control of a hydraulically amplified self-healing electrostatic (HASEL) actuator

Schunk, C., Pearson, L., Acome, E., Morrissey, T. G., Correll, N., Keplinger, C., Rentschler, M. E., Humbert, J. S.

In 2018 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2018), pages: 6417-6423, IEEE, Piscataway, NJ, IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2018), October 2018 (inproceedings)

Abstract
This paper describes a system identification method and the development of a closed-loop controller for a Hydraulically Amplified Self-healing Electrostatic (HASEL) actuator. Our efforts focus on developing a reliable and consistent way to identify system models for these soft robotic actuators using high-speed videography based motion tracking. Utilizing a mass-spring-damper model we are able to accurately capture the behavior of a HASEL actuator. We use the resulting plant model to design a Proportional-Integral controller that demonstrates improved closed-loop tracking and steady-state error performance.

link (url) DOI [BibTex]

2018

Schunk, C., Pearson, L., Acome, E., Morrissey, T. G., Correll, N., Keplinger, C., Rentschler, M. E., Humbert, J. S. System identification and closed-loop control of a hydraulically amplified self-healing electrostatic (HASEL) actuator In 2018 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2018), pages: 6417-6423, IEEE, Piscataway, NJ, IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2018), October 2018 (inproceedings)

link (url) DOI [BibTex]

2012

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Modeling Guided Design of Dielectric Elastomer Generators and Actuators

Li, T., Qu, S., Keplinger, C., Kaltseis, R., Baumgartner, R., Bauer, S., Suo, Z., Yang, W.

In Proceedings of the SPIE 8340, Electroactive Polymer Actuators and Devices conference, pages: 83401X, April 2012 (inproceedings)

Abstract
Mechanical energy and electrical energy can be converted to each other by using a dielectric elastomer transducer. Large voltage-induced deformation has been a major challenge in the practical applications. The voltage-induced deformation of dielectric elastomer is restricted by electromechanical instability (EMI) and electric breakdown. We study the loading path effect of dielectric elastomer and introduce various methods to achieve giant deformation in dielectric elastomer and demonstrate the principles of operation in experiments. We use a computational model to analyze the operation of DE generators and actuators to guide the experiment. In actuator mode, we get three designing parameters to vary the actuation response of the device, and realize giant deformation with appropriate parameter group. In the generator mode, energy flows in a device with inhomogeneous deformation is demonstrated.

DOI [BibTex]

2012

Li, T., Qu, S., Keplinger, C., Kaltseis, R., Baumgartner, R., Bauer, S., Suo, Z., Yang, W. Modeling Guided Design of Dielectric Elastomer Generators and Actuators In Proceedings of the SPIE 8340, Electroactive Polymer Actuators and Devices conference, pages: 83401X, April 2012 (inproceedings)

DOI [BibTex]

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Inhomogeneous Deformation and Instability in Soft Dielectric Transducers

Li, T., Qu, S., Keplinger, C., Suo, Z., Yang, W.

In Proceedings of the APS March Meeting 2012, 57(1), Boston, USA, March 2012 (inproceedings)

Abstract
Dielectric elastomer (DE) is assembled by sandwich an elastomeric membrane with compliant electrodes on both sides. They are capable of converting mechanical into electrical energy (generator)or electrical into mechanical energy (actuator). The large actuation strain of DE has inspired intense development of dielectric elastomers as applications as actuators and generators. DE transducers are lightweight, compliant, rust-free, and can convert higher energy than those of conventional transducers. DE transducers often undergo inhomogeneous deformation and instability during operation. Inhomogeneous deformation can cause the DE membranes in have inhomogeneous fields distribution and fail locally. Instability during actuation highly affects the performance and safety of the DE transducer. We present an analyitial model of a dielectric elastomer transducers undergoing inhomogeneous deformation and snap-through instability during operation.

[BibTex]

Li, T., Qu, S., Keplinger, C., Suo, Z., Yang, W. Inhomogeneous Deformation and Instability in Soft Dielectric Transducers In Proceedings of the APS March Meeting 2012, 57(1), Boston, USA, March 2012 (inproceedings)

[BibTex]

2011

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Dielectric Elastomers: From the Beginning of Modern Science to Applications in Actuators and Energy Harvesters

Baumgartner, R., Keplinger, C., Kaltseis, R., Schwödiauer, R., Bauer, S.

In Proceedings of the SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring conference, San Diego, USA, 2011 (inproceedings)

Abstract
Electrically deformable materials have a long history, with first quotations in a letter from Alessandro Volta. The topic turned out to be hot at the end of the 19th century, with a landmark paper of Röntgen anticipating the dielectric elastomer principle. In 2000, Pelrine and co-workers generated huge interest in such soft actuators, by demonstrating voltage induced huge area expansion rates of more than 300%. Since then, the field became mature, with first commercial applications appearing on the market. New frontiers also emerged recently, for example by using dielectric transducers in a reverse mode for scavenging mechanical energy. In the present survey we briefly discuss the latest developments in the field.

DOI [BibTex]

2011

Baumgartner, R., Keplinger, C., Kaltseis, R., Schwödiauer, R., Bauer, S. Dielectric Elastomers: From the Beginning of Modern Science to Applications in Actuators and Energy Harvesters In Proceedings of the SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring conference, San Diego, USA, 2011 (inproceedings)

DOI [BibTex]

2010

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Modeling of Inhomogeneous Deformation in a Dielectric Elastomer Generator for Energy Harvesting

Li, T., Keplinger, C., Liu, L., Baumgartner, R., Qu, S.

In Proceedings of the ASME 2010 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, pages: 267, Philadelphia, USA, September 2010 (inproceedings)

Abstract
Dielectric elastomer transducers promise to combine high energy density at low cost and lightweight when used as actuators or for energy harvesting generators. A cornucopia of possible applications have been demonstrated over the last years including soft matter based actuators for robotics, tunable optics, medical devices, space robotics and energy harvesters. Prestretch effects and the electromechanical instability have been shown to highly influence the performance of dielectric elastomer transducers. Nevertheless only sparse research has been done on instability and prestretch effects of dielectric elastomer membranes under inhomogeneous deformation. Dielectric elastomer transducers consist of an elastomer membrane sandwiched between a pair of compliant electrodes and can be considered as deformable capacitors with variable capacitance. Here we focus on a specific experimental setup well suited to study the performance of dielectric elastomer materials for energy harvesting. In this setup an elastomer membrane is equibiaxially prestretched and fixed on top of an air chamber which is connected to a compressed air reservoir, the source of mechanical energy for thegenerator. From the electrical point of view the compliant electrodes on the elastomer membrane can be connected to both a high and low voltage charge reservoir. Thus the change in capacitance during deformation can be used to boost charges from the low voltage reservoir to the high voltage reservoir. Experimentally, different constant voltages are applied to the elastomer membrane during inflation and the air chamber pressure is recorded together with the shape and the volume of the balloon for different initial prestretches. The usual instability in the pressure-volume curves of ballon inflation experiments are shown to be influenced by applied voltage and prestretch. Theoretically, the setup is modeled as a thermodynamic system, with static electric and mechanical load where quasi-static equilibrium states can be achieved. To describe the inhomogeneous deformation and to correctly account for the hyperelastic behavior of the material over the whole deformation range an asymmetric model is built based on the Arruda-Boyce material model. The results of the numerical simulation are fitted to the experimental data to obtain significant material parameters in order to predict the optimal operation regime of the dielectric elastomer generator. The experimental results accompanied by the theoretical analysis may be used as a benchmark for the applicability of dielectric elastomer generators and pave ways for understanding the dielectric elastomer behavior under inhomogeneous deformation.

DOI [BibTex]

2010

Li, T., Keplinger, C., Liu, L., Baumgartner, R., Qu, S. Modeling of Inhomogeneous Deformation in a Dielectric Elastomer Generator for Energy Harvesting In Proceedings of the ASME 2010 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, pages: 267, Philadelphia, USA, September 2010 (inproceedings)

DOI [BibTex]

2008

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Analysis of Safe and Failure Mode Regimes of Dielectric Elastomer Actuators

Kaltenbrunner, M., Keplinger, C., Arnold, N., Bauer, S.

In Proceedings of the IEEE SENSORS 2008 Conference, pages: 156-159, Lecce, Italy, October 2008 (inproceedings)

Abstract
Dielectric elastomer actuators (DEAs) are promising for bionic and robotic applications. Reliability requirements in such applications necessitate better knowledge of the safe operation regimes and possible failure modes of DEAs. Elastomers consist of a network of entangled and cross-linked polymer chains, able to sustain spatially varying stress and strain fields, accompanied by stored elastic energy. Here we introduce a rigorous thermodynamic description of DEAs, based on a statistical mechanical model to gain insight for material development and optimization. We investigate multistability effects in the phase diagrams of elastomer actuators and combine our model with capacitive extensometry experiments.

DOI [BibTex]

2008

Kaltenbrunner, M., Keplinger, C., Arnold, N., Bauer, S. Analysis of Safe and Failure Mode Regimes of Dielectric Elastomer Actuators In Proceedings of the IEEE SENSORS 2008 Conference, pages: 156-159, Lecce, Italy, October 2008 (inproceedings)

DOI [BibTex]

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Cellular Ferroelectrets for Soft Matter Integrated Devices with Advanced Functionality

Schwodiauer, R., Graz, I., Kaltenbrunner, M., Keplinger, C., Bartu, P., Buchberger, G., Ortwein, C., Bauer, S.

In Proceedings of the 13th International Symposium on Electrets, Tokyo, Japan, September 2008 (inproceedings)

Abstract
In this paper, a selection of some functional polymer elements are introduced, interfacing with thin film transistors is discussed and an example for a flexible touchpad of utmost simplicity is presented. This leads to thin stretchable transducer- and sensor skin arrays which we propose. Special emphasis is laid on piezoelectric cellular ferroelectrets which offer not only a wealth of applications but seem also ideally suited as efficient electroactive materials for a low cost all- polymer device technology.

DOI [BibTex]

Schwodiauer, R., Graz, I., Kaltenbrunner, M., Keplinger, C., Bartu, P., Buchberger, G., Ortwein, C., Bauer, S. Cellular Ferroelectrets for Soft Matter Integrated Devices with Advanced Functionality In Proceedings of the 13th International Symposium on Electrets, Tokyo, Japan, September 2008 (inproceedings)

DOI [BibTex]

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Cellular Ferroelectrets for Electroactive Polymer Hybrid Systems: Soft Matter Integrated Devices with Advanced Functionality

Schwödiauer, R., Graz, I., Kaltenbrunner, M., Keplinger, C., Bartu, P., Buchberger, G., Ortwein, C., Bauer, S.

In Proceedings of the SPIE Vol. 6927 , pages: 69270Q 1-10, San Diego, USA, April 2008 (inproceedings)

Abstract
Thin polymer foams with a closed cell void-structure can be internally charged by silent or partial discharges within the voids. The resulting material, which carries positive and negative charges on the internal void surfaces is called a ferroelectret. Ferroelectrets behave like typical ferroelectrics, hence they provide a novel class of ferroic materials. The soft foams are strongly piezoelectric in the 3-direction, but show negligible piezoelectric response in the transverse direction. This, together with a very low pyroelectric coefficient, make ferroelectrets highly suitable for flexible electroactive transducer element which can be integrated in thin bendable organic electronic devices. Here we describe some fundamental characteristics of cellular ferroelectrets and present a number of promising examples for a possible combination with various functional polymer systems. Our examples focus on flexible ferroelectret field-effect transistor systems for large-area sensor skins and microphones, flexible large-array position detectors (touchpad), and stretchable large-array pressure sensors.

DOI [BibTex]

Schwödiauer, R., Graz, I., Kaltenbrunner, M., Keplinger, C., Bartu, P., Buchberger, G., Ortwein, C., Bauer, S. Cellular Ferroelectrets for Electroactive Polymer Hybrid Systems: Soft Matter Integrated Devices with Advanced Functionality In Proceedings of the SPIE Vol. 6927 , pages: 69270Q 1-10, San Diego, USA, April 2008 (inproceedings)

DOI [BibTex]

2005

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Piezoelectric Polymers

Bauer, S., Bauer-Gogonea, S., Dansachmüller, M., Dennler, G., Graz, I., Kaltenbrunner, M., Keplinger, C., Reiss, H., Sariciftci, N. S., Singh, T. B., Schwödiauer, R.

In Proceedings of the Symposium W – Electroresponsive Polymers and Their Applications , 889, pages: 0889-W01-02, 2005 (inproceedings)

Abstract
The science and technology of piezoelectric polymers has long been dominated by ferroelectric polymers from the polyvinylidene fluoride (PVDF) family. The piezoelectricity in this polymer class arises from the strong molecular dipoles within the polymer chain and from the resulting change of the dipole density upon application of a mechanical stimulus. Ferroelectric polymers show moderate piezoelectric coefficients (d33 and d31,32 around 20-30 pC/N) in comparison to ceramic piezoelectrics, with an acoustic impedance comparable to that of water. The thermal stability of the piezoelectric effect is limited to below 100°C, though stability up to 125°C has recently been announced. Applications of ferroelectric polymers emerged in many niches. A good example of a success story for PVDF applications are clamp-on transducers used as pressure sensor for Diesel injection lines, with selling numbers over 50 million pieces per year. A relatively new development are relaxor ferroelectric polymers, based on electron-irradiated poly(vinylidene fluoride) trifluoroethylene copolymers or on terpolymers of vinylidene fluoride, trifluoroethylene and chlorofluoroethylene. Relaxor ferroelectric copolymers exhibit strong electrostriction and thus large piezoelectric coefficients, when used under electric dc-bias fields. Internally charged cellular polymer foam electrets (ferroelectrets) resemble close similarities to ferroelectrics. They display large intrinsic piezoelectric d33-coefficients well above 100 pC/N and very small d31 and d32 coefficients, coupled with a limited thermal stability up to 50°C in the polypropylene workhorse material. The materials are pioneered in Finland and already entered the market in niches, for example in musical pick-ups. They promise large area applications, for example in surveillance and intruder systems. Finally, organic semiconductors have shown a rather unusual electromechanical response, governed by a power law S=V3/2 of strain S versus voltage V, located in between traditional piezoelectricity and electrostriction. The field of piezoelectric polymers therefore received new stimulus, and the material class of piezoelectric polymers has been significantly broadened recently.

DOI [BibTex]

2005

Bauer, S., Bauer-Gogonea, S., Dansachmüller, M., Dennler, G., Graz, I., Kaltenbrunner, M., Keplinger, C., Reiss, H., Sariciftci, N. S., Singh, T. B., Schwödiauer, R. Piezoelectric Polymers In Proceedings of the Symposium W – Electroresponsive Polymers and Their Applications , 889, pages: 0889-W01-02, 2005 (inproceedings)

DOI [BibTex]