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Polymer actuators

Introduction

Conjugated polymers (CP) such as polypyrrole (PPy) can be electrochemically oxidized and reduced. This leads amongst others to a volume change due to the intercalation of ions and solvent swelling. This volume change can be used to create (micro-)actuators.

We are currently working on:

  • New materials development, including hybrid EAP materials
  • Micromechanical stimulation of cells
  • Micromechanics and microrobotics
  • Novel actuator designs
  • Novel farbication methods for CP microactuators
  • Development of microactuators that function in-air

For more information or research opportunities contact dr. Edwin Jager.

Publications

Our actuator publications can be found here.

Recent results

Novel actuators based on polypyrrole/carbide-derived carbon hybrid materials

Polypyrrol (PPy) hybrid films incorporated with porous carbide-derived carbon (CDC) particles are synthesized through a novel one-step electrochemical synthesis process that provides a simple and efficient alternative for current tape-casting and inkjet printing technologies to make conducting polymer–CDC-based electroactive composites. The resulting porous, robust and electrically conductive hybrid layer was used to fabricate electroactive polymer actuators both as perpendicularly expanding actuators and as bending trilayer actuators. Raman and FTIR spectroscopy confirm successful incorporation of CDC in the PPy matrix. Cyclic voltammograms confirm slightly higher charging/discharging currents of the PPyCDC hybrid. This indicates the successful coupling of CDC in order to increase electric double-layer capacitance in the hybrid films. The maximum steady state electromechanical diametrical strain is 13% for hybrid material which is in the same order of magnitude as for PPy and 10x more than previously reported CDC films made with non-conducting polymer binders. Furthermore, the expanding actuators made from hybrid material are more efficient than non-modified PPy actuators, having doubled the amount of swelling per injected charge. This improvement is very important since the low energy efficiency is a major shortcoming for ionic electroactive polymers. The high pseudocapacitance makes these new hybrid materials also interesting for energy storage applications.

Full article or DOI:10.1016/j.carbon.2014.08.078

J. Torop, A. Aabloo, E. W. H. Jager, Carbon, 2014, 80, p.387.

Effect of the Electrolyte Concentration and Substrate on Conducting Polymer Actuators

The effect of the electrolyte concentration (NaCl aqueous electrolyte) on the dimensional variations of films of polypyrrole doped with dodecylbenzenesulfonate PPy(DBS) on Pt and Au wires was studied. Any parallel reaction that occurs during the redox polymeric reaction that drives the mechanical actuation, as detected from the coulovoltammetric responses, was avoided by using Pt wires as substrate and controlling the potential limits, thus significantly increasing the actuator lifetime. The NaCl concentration of the electrolyte, when studied by cyclic voltammetry or chronoamperometry, has a strong effect on the performance as well. A maximum expansion was achieved in 0.3 M aqueous solution. The consumed oxidation and reduction charges control the fully reversible dimensional variations: PPy(DBS) films are faradaic polymeric motors. Parallel to the faradaic exchange of the cations, osmotic, electrophoretic, and structural changes play an important role for the water exchange and volume change of PPy(DBS).

Full article or DOI: 10.1021/la404353z

J. G. Martinez, T. F. Otero, E. W. H. Jager, Langmuir, 2014, 30, p.3894.

The effect of film thickness on polypyrrole actuation assessed using novel non-contact strain measurements

The volume change of the electro-active polymer polypyrrole has been used to build (micro-)actuators.  The strain regime is inherently complex at a physical level and whilst volume change can be estimated indirectly using, for instance, bending beam theory, such methods become unreliable for large deflections owing to limitations in the mathematical model. In this work we developed a new non-contact measuring technique based on a laser scanner micrometer to characterize the time-dependent expansion of electro-active films such as polypyrrole. Measurements have been made which demonstrate that the observed strain is dependent on film thickness. The new measurement technique is straightforward to perform and it is anticipated that it can be used for future materials development and performance assessment, including long-term stability evaluations and operational failure studies of the films.

Full article or DOI: 10.1088/0964-1726/22/10/104021

D. Melling, S. Wilson, E.W.H. Jager,  Smart Materials & Structures, 2013, 22, 104021.
 

Thin Film Free Standing PEDOT:PSS/SU8 Bilayer Microactuators

A variety of active materials have been used to construct microactuators. We developed novel all-polymer electrochemical microactuators, based on conductive ultra-thin films made of the conjugated polymer poly(3, 4-ethylenedioxythiophene) doped with the polyanion poly(styrenesulfonate) (PEDOT:PSS) as well as novel processing method for manufacturing thereoff. We fabricated and patterned free-standing PEDOT:PSS/SU8 bilayer microactuators in the form of microfingers of a variety of lengths using adapted microfabrication procedures. By imposing electrochemical oxidation/reduction cycles on the PEDOT:PSS we were able to demonstrate reversible actuation of the microactuators resulting in bending of the microfingers. A number of possible applications can be envisaged for these small, soft actuators, such as microrobotics and cell manipulation.

Full article or DOI:10.1088/0960-1317/23/11/117004

S. Taccola, F. Greco, B. Mazzolai, V. Mattoli, E. W. H. Jager, J. Micromech. Microeng. , 2013, 23, 117004
 

Propulsion of swimming microrobots inspired by metachronal waves in ciliates: from biology to material specifications

The quest for swimming microrobots originates from possible applications in medicine, especially involving navigation in bodily fluids. Swimming microorganisms have become a source of inspiration because their propulsion mechanisms are effective in the low-Reynolds number regime. In this study, we address a propulsion mechanism inspired by metachronal waves, i.e. the spontaneous coordination of cilia leading to the fast swimming of ciliates. We analyse the biological mechanism Paramecium caudatum and we investigate the contribution of its main features to the swimming performance, through a 3Dl finite-elements model, in order to develop a simplified, yet effective artificial design. We propose a bioinspired propulsion mechanism for a swimming microrobot based on a continuous cylindrical electroactive surface exhibiting perpendicular wave deformations travelling longitudinally along its main axis. The simplified propulsion mechanism is conceived specifically for microrobots that embed a micro-actuation system capable of executing the bioinspired propulsion (self-propelled microrobots). Among the available electroactive polymers, we select polypyrrole as the possible actuation material and we assess it for this particular embodiment. The results are used to appoint target performance specifications for the development of improved or new electroactive materials to attain metachronal-waves-like propulsion.

Full article or DOI:10.1088/1748-3182/8/4/046004

S. Palagi, E.W.H. Jager, B. Mazzolai, L. Beccai, Bioinspiration & Biomimetics, 2013, 8, 046004.
 

Patterning and electrical interfacing of individually controllable conducting polymer microactuators

Conducting polymer actuators such as polypyrrole (PPy) microactuators are interesting candidates to drive autonomous microrobotic devices that require low weight and low power. Simple PPy tri-layer bending type microactuators that operate in air have been demonstrated previously but they lack individual control and had problems with short circuiting due to electrical connections. The lack of micropatterning methods and proper interfacing are currently major obstacles in the development of PPy tri-layer microactuators. We developed for the first time methods for successfully patterning and interfacing of such tri-layer PPy microactuators. The PPy tri-layer actuators were patterned using adapted microfabrication technology including photolithography. The interface was based on a flexible printed circuit board comprising the electronic circuit into which the actuator unit was embedded. It showed that the microfabricated tri-layer actuators functioned as good as the normally fabricated actuators. The new interface seemed to actually improve the actuator performance. This interfacing method could also be applied to other electroactive polymer devices, such as ion polymer metal composites (IPMC) and dielectric elastomers (DE).

Full article or DOI:10.1016/j.snb.2013.02.075

E.W.H. Jager, N. Masurkar, N.F. Nworah, B. Gaihre, G. Alici, G.M. Spinks, Sensors and Actuators B: Chemical, 2013, 183, p.283.
 

Mechanical Stimulation of MDCK Epithelial Cells Using PPy Microactuators

We developed a microfabricated chip comprising poplypyrrole microactuators that were used to mechanically stimulate single cells. Renal epithelial (MDCK) cells were cultured on top of the microactuator chip. The MDCK cells adheared and spread well on the surface of the chip. The PPy actuators expanded upon the application of a low potential and stretched the MDCK cells that spanned over a border, thus mechanically stimulating individual cells. The response to this stimulation was monitored as an increase in intracellular Ca2+. We were able to identify that Ca2+ response was clearly associated by the mechanical stimulation of the cells and that it was caused by an autocrine ATP signalling pathway.

Full article or DOI: 10.1039/C1LC20436J

Karl Svennersten, Magnus Berggren, Agneta Richter-Dahlfors and Edwin W. H. Jager, Lab on a Chip, 2011, 11, p.3287

Previous work

Microrobots for Micrometer-Size Objects in Aqueous Media: Potential Tools for Single Cell Manipulation

Conducting polymers, such as polypyrrole (PPy) are excellent materials for actuators that are operated in aqueous media. Microactuators based on polypyrrole-gold bilayers enable large movement of structures attached to these actuators and are of particular interest for the manipulation of biological objects, such as single cells. We developed a new fabrication method in order to create individually addressable and controllable PPy-microactuators. We designed and fabricated micrometer-size manipulator, or microrobotic arm, using these individually controlled PPy-microactuators. This microrobotic arm can pick up, lift, move, and place micrometer-size objects making the microrobot an excellent tool for single-cell manipulation.

Full article or DOI:10.1126/science.288.5475.2335

Edwin W. H. Jager, Olle Inganäs, Ingemar Lundström, Science, 2000, 288, p.2335.
 


Responsible for this page: Edwin Jager
Last updated: 04/02/15