Artificial Muscle Preparation Procedure Using

Polypyrrole and a Solid Polymer Electrolyte*

J.M. Sansiñena and V. Olazábal
NDEAA Group, Jet Propulsion Laboratory (JPL), USA

* This preparation procedure is based on the work that Dr. J.M. Sansiñena and Dr. V. Olazábal developed in collaboration with Prof. Marco-A. De Paoli and Dr. C.N. Polo da Fonseca during their visit at the Laboratory of Conducting Polymers of the Institute of Chemistry at the UNICAMP University (Brazil). This work was a part of their Ph.D. studies under the guidance of Prof. T.F. Otero.


·        Monomer: Pyrrole (distillate under 50 mmHg vacuum conditions and 59 0C).

·        Base polymer of the solid polymer electrolyte: poly (epichlorohydrin-co-ethylene oxide) (P [ECH-co-EO]).

·        Lithium Perchlorate (LiClO4).

·        Acetonitrile HPLC grade (ACN).

·        Tetrahydrofuran HPLC grade (THF).

·        Deionized water.

·        Electrodes: Polished stainless steel plates (Length: 2.5 cm, Width: 1.5 cm).

Electrochemical synthesis of the PPY films

Polypyrrole films are synthesized under an inert atmosphere of nitrogen from 0.2 M pyrrole and 0.1 M LiClO4 acetonitrile (2% water content) solutions. Three stainless steel plates are used as electrodes, one of them as working electrode and the other two are connected in parallel as counter-electrodes. The working electrode is positioned face to face between two counter-electrodes at 1 cm from each one. A saturated calomel electrode is used as reference electrode.

The electrochemical synthesis of PPY films is carried out applying a potential square wave between -300 mV (2 s) and 850 mV (8 s). The process is stopped when the polymerization electric charge (Q850mV – Q-300mV) is 5 At this moment 1 of PPY is electrodeposited on each side of the electrode (thickness = 6 μm). Finally the coated electrode is extracted from the solution, rinsed in acetonitrile and dried in air for 2 hours.

Preparation of the HYDRIN solution

A 2.5 wt% solution of poly (epichlorohydrin-co-ethylene oxide) (P [ECH-co-EO]) in tetrahydrofuran (THF) is prepared. Later LiClO4 (0.1312 grams of LiClO4 per gram of P[ECH-co-EO]) is added and stirred for 30 minutes to obtain the HYDRIN solution. The quantity of LiClO4 added is the optimum concentration (η = [O]/[Li+] = 6) to give the highest ionic conductivity in the HYDRIN film that will be later obtained by casting.

Construction of the Artificial Muscle

The artificial muscle consists of two polypyrrole (PPY) films separated by a HYDRIN film. The HYDRIN is placed between the two PPY films to allow ionic conduction. Be careful to avoid any parasitic electrical contact between the two PPY films.

The triple layer [PPY || HYDRIN || PPY] is constructed dripping HYDRIN solution on two PPY films (150 μl of HYDRIN solution in each PPY film), which are previously electrodeposited on two different stainless steel electrodes (1). Once the HYDRIN is viscous and adherent enough the two electrodes are put in contact and a [steel || PPY || HYDRIN || PPY|| steel] system is performed (2). After 30 minutes the HYDRIN is dry enough and the triple layer [PPY|| HYDRIN || PPY] is peeled off the stainless steel plates (3).

Once the triple layer [PPY|| HYDRIN || PPY] is made, a PPY film is connected as a working electrode and the other one as a counter-electrode short-circuited to the reference electrode connector of the potentiostat/galvanostat instrument. This triple layer can be electroactived in air when an electric field is applied through the two PPY films. This movement in air is described in the following reference:

J.M. Sansiñena, V. Olazábal, T.F. Otero, C.N. Polo da Fonseca, M-A. De Paoli, Chem. Commun., 1997 2217


The editor of the WW-EAP Webhub would like to express his sincere appreciation to Dr. José-María Sansiñena and Dr. Virginia Olazábal for their contribution. Their effort demonstrated the ability to produce EAP-based artificial muscles that are made of conducting polymers, which do not require liquid environment.