11 Professor: Dr. Cheng-Hsien Liu ( 劉承賢教授 ) Student: Han-Yi Chen ( 陳翰儀 ) Student ID: Date: Sensing and Actuation in Miniaturized Systems Mass-production-oriented Ionic Polymer Actuator Based on Engineered Material Structure Author: N. Nagai, T. Kawashima, J. Ohsako Sony Corporation, Kitashinagawa Shinagawa-ku, Tokyo, JAPAN

2 Han-Yi Chen, NEMS, NTHU, 11/10/2009 2Outline Introduction Experiments and results Bending mechanism Conclusions Applications of ionic polymer actuator Advantages and issues of ionic polymer actuator New ionic polymer actuator Theory Verification Structure Manufacturing process Basic characteristics References Electrode Ion conductive polymer

Introduction

4 Han-Yi Chen, NEMS, NTHU, 11/10/ Applications: Artificial muscle Biomimetic sensors Biomimetic actuators Advantages: High performance in displacement or output force Light weight Flexibility Issues: Inefficiency of production process High cost of materials Ionic Polymer Actuator Ref.: High performance High productivity Simple process Common instrument High performance High productivity Simple process Common instrument New ionic polymer actuator

Experiments and Results

6 Han-Yi Chen, NEMS, NTHU, 11/10/ Carbon electrode Structure and Manufacturing Process Ion-exchange polymer membrance (perfluorosulfonic acid polymer & ionic liquid) Carbon electrode (fine carbon particles & perfluorosulfonic acid polymer & ionic liquid) Metal Ion-exchange polymer membrance Carbon electrode Metal Ion exchange polymer dispersion Carbon powder Ionic liquid Zircon beads Spray coating process Ion-exchange membrance Carbon electrode Structure Manufacturing process Heating & pressing Perfluorosulfonic acid polymer SEM cross section view

7 Han-Yi Chen, NEMS, NTHU, 11/10/ Basic Characteristics (1) Displacement 15 mm Time (sec) Displacement (mm) Time (sec) Displacement (mm) Bending motion of the actuator (2 V, 0.1 Hz) Displacement of an actuator under applied constant voltage 2 V 0 to 30 sec 0 to 2000 sec Air The actuator bends to one side by applying constant positive voltage and bends to the other side if change the voltage to negative The displacement at 30 s after applying voltage 2.0 V was about 5 mm. After 30 s the displacement began to decrease gradually and finally it reversed its movement and bent to the other side regarding its initial position. The actuator bends to one side by applying constant positive voltage and bends to the other side if change the voltage to negative The displacement at 30 s after applying voltage 2.0 V was about 5 mm. After 30 s the displacement began to decrease gradually and finally it reversed its movement and bent to the other side regarding its initial position. W: 2 mm L: 30 mm

8 Han-Yi Chen, NEMS, NTHU, 11/10/ Basic Characteristics (2) Time (sec) Displacement (mm) 10 mA 5 mA 1 mA Displacements under applied constant currents Dependence of output force on applied constant voltage The displacement is in proportion to the period of applying constant current. The output force was increased as applying voltage, and the force was over 4 mN at 2.0 V. Applied Voltage (V) Output Force (gf)

Bending Mechanism

10 Han-Yi Chen, NEMS, NTHU, 11/10/ Theory Bending model for an ionic polymer actuator (a) Status without applying voltage (b) Initial motion of ions and bending (c) Bending after most of cations moved The motion of ionic polymer actuator: Initial fast bending: different moving speed Subsequent slow bending to inverse direction: different size Cations move much faster than anions Anions is much larger than cations Anions is much larger than cations

11 Han-Yi Chen, NEMS, NTHU, 11/10/ Verification (1)- Verification (1)- Verify the Difference of Speed Between Ions A test piece for measuring potential distribution Transition of potential distribution after applying 2V - + Ion conductive polymer Carbon electrode Ionic liquid added section Au plated solid electrodes 2 V Base 50 µm < 0.5 V ~ 1 V At 0 s: potential transition is at the center: slight shift on the distribution of ionic liquid. At 1000 s: potential transition moved to neighborhood of both carbon electrodes: electric double layer formed by ionic liquid at the carbon electrode. At 6000 s: the electric double layer formed by cations is almost completed and potential transition at this point is close to 1V. Whereas the electric double layer formed by anions is not completed and the potential transition is less than 0.5V. Proof: moving speed of cations is faster than anion.

12 Han-Yi Chen, NEMS, NTHU, 11/10/ Carbon electrode Ion conductive polymer Ionic Liquid added section Verification (2)- Verification (2)- Estimate Moving Speed of Ions A test piece for measuring charging current Charging current of a test piece at applying constant voltage 2V (a) The actuator electrically behaves as a capacitor with wide gap and the current is small sharp peak at initial stage. The speed of cation: 50 µm / 2000 s = 25 nm/s The speed of anion: 50 µm / s = 1.3 nm/s The cation is about 20 times faster than the anion. The speed of cation: 50 µm / 2000 s = 25 nm/s The speed of anion: 50 µm / s = 1.3 nm/s The cation is about 20 times faster than the anion. Current by faster ion (cation) Current by slower ion (anion) 2000 s (a) (b) (c) (d) (b) Then the charging current keeps small value while the ions migrate through the ion exchange polymer. (c) Finally the ions arrive at carbon electrode and begin to form an electric double layer. The current increases rapidly at that point as capacitance increases simultaneously. (d) After accomplishing the electric double layer, the charging current rapidly decreases and begins to keep small value again.

13 Han-Yi Chen, NEMS, NTHU, 11/10/ Verification (3)- Verification (3)- Factors of Different Ion Speed Carbon electrode Ion conductive polymer Ionic Liquid added section A test piece for measuring charging current The factors to make anion speed slow: Ion size: the size of anion is about two times bigger than cation Interaction between anion and functional group: (1) Perfluorosulfonic acid polymer is a cation exchange polymer so that anions can not pass through the actuator basically. (2) The anions could pass by applying enough voltage. The threshold voltage was about 100 mV. But the moving speed is very slow because the anions is scattered by functional group.

Conclusions

15 Han-Yi Chen, NEMS, NTHU, 11/10/ The author developed practical designed polymer actuator with high performance in the air. They clarify a bending mechanism of their polymer actuator that the differences in size and in moving speed between cations and anions cause bending. They think that interaction between ion and functional group of polymer decides the size and the moving speed of ions. The polymer actuator they developed is easy to change the materials and the process so that they think this actuator can improve the performance further more. This actuator will make lighter and smaller device possible in the market in future. Conclusions

16 Han-Yi Chen, NEMS, NTHU, 11/10/ References [1] K. Oguro, Y. Kawami, H. Takenaka “Bending of an ion- conducting polymer film-electrode composite by an electric stimulus at low-voltage.” J. Micromach. Soc. 5 (1992) 27–30. [2] M. Shahinpoor, Y. Bar-Cohen, J. Simpson, J. Smith “Ionic polymermetal composites (IPMCs) as biomimetic sensors, actuators and artificial muscles—a review. ” Smart Mater. Struct. 7 (1998) R15-R30. [3] Barbar J. Akle, Matthew D. Bennett, Donald J. Leo “High-strain ionomeric–ionic liquid electroactive actuators” Sensors and Actuators A 126 (2006) 173–181

17 Han-Yi Chen, NEMS, NTHU, 11/10/ Thank you for your attention!!

18 Han-Yi Chen, NEMS, NTHU, 11/10/ The effects of electrode expansion: Mainly determined by original ion size and by repulsive force between same ions. The interaction between ions and functional group. But the amount of ions is much larger than functional group at the electrode.