Limits...
Design and fabrication of a large-stroke deformable mirror using a gear-shape ionic-conductive polymer metal composite.

Wei HC, Su GD - Sensors (Basel) (2012)

Bottom Line: Finally, a gear shaped IPMC actuator was designed and tested.Optical power of the IPMC deformable mirror is experimentally demonstrated to be 17 diopters with two volts.The needed voltage was about two orders lower than conventional silicon deformable mirrors and about one order lower than the liquid lens.

View Article: PubMed Central - PubMed

Affiliation: Graduate Institute of Photonics and Optoelectronics, National Taiwan University, No. 1, Roosevelt Road, Section 4, Taipei 10617, Taiwan. d96941017@ntu.edu.tw

ABSTRACT
Conventional camera modules with image sensors manipulate the focus or zoom by moving lenses. Although motors, such as voice-coil motors, can move the lens sets precisely, large volume, high power consumption, and long moving time are critical issues for motor-type camera modules. A deformable mirror (DM) provides a good opportunity to improve these issues. The DM is a reflective type optical component which can alter the optical power to focus the lights on the two dimensional optical image sensors. It can make the camera system operate rapidly. Ionic polymer metal composite (IPMC) is a promising electro-actuated polymer material that can be used in micromachining devices because of its large deformation with low actuation voltage. We developed a convenient simulation model based on Young's modulus and Poisson's ratio. We divided an ion exchange polymer, also known as Nafion(®), into two virtual layers in the simulation model: one was expansive and the other was contractive, caused by opposite constant surface forces on each surface of the elements. Therefore, the deformation for different IPMC shapes can be described more easily. A standard experiment of voltage vs. tip displacement was used to verify the proposed modeling. Finally, a gear shaped IPMC actuator was designed and tested. Optical power of the IPMC deformable mirror is experimentally demonstrated to be 17 diopters with two volts. The needed voltage was about two orders lower than conventional silicon deformable mirrors and about one order lower than the liquid lens.

No MeSH data available.


Schematics of the electro-osmotic migration of hydrated counter-ions within the IPMC network. Black bars and red balls stand for hydrophilic side chains and hydrophobic main chains, respectively.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3472876&req=5

f1-sensors-12-11100: Schematics of the electro-osmotic migration of hydrated counter-ions within the IPMC network. Black bars and red balls stand for hydrophilic side chains and hydrophobic main chains, respectively.

Mentions: Ionic polymer-metal composite (IPMC) is a promising alternative material for use in fabricating MEMS-based DMs because of its ability to exhibit large bidirectional actuation with low applied voltage. Figure 1 shows the schematics of the electro-osmotic migration of hydrated counter-ions within the IPMC network. It is a sandwich structure with a layer of Nafion® inside and two layers of metal outside as the electrodes. The chemical formula of Nafion® can be separated into two chains. The hydrophobic main chain forms the backbones to determine the mechanical strength, which is the black bar. The hydrophilic side chain terminated by ionic groups, such as SO3− for cation exchange, is the red ball noted fixed anion. The working principle of IPMC actuation is that when an electric field is applied, hydrated cations move through the cluster networks which are formed by the chains towards the cathode so that the volume expands near the cathode side and contracts near the anode side. As a results the IPMC bends toward the anode. According to the actuation mechanism, the real internal stress inside Nafion® should be symmetric and linear distributed along its thickness [6], which is positive in one layer and is negative in another layer of Nafion®. Traditionally, the IPMC in cantilever beam shape can only generate bending motions, but actuators with the capability of complex deformation are highly desirable in many applications. Pugal et al. [7] presented an electrode patterned IPMC with a twist motion for bionics applications. In recent works [8], we proposed a three-deformational gray box model based on the finite element method (FEM). According to this model, the deformation of IPMC in arbitrary shapes which were confined with different boundaries can be predicted more easily. Therefore, arbitrary deformation can be achieved and pre-designed. In this work, a gear-shape IPMC was designed and demonstrated to deform like a rotationally symmetric, or aspheric, surface. The experimental results agreed well with the simulation data which will be discussed in the latter sections. However, IPMC is known for practical challenges, such as reliability in dry air and the back-relaxation phenomenon. This is mainly due to the actuation mechanism which depends on the movement of hydrated cations inside it. Therefore, the effects of water content on the actuation performance of ionic polymer–metal composites are quite important [9]. Thereafter, encapsulation processes applied to IPMCs are nowadays a critical subject to their practical use. PDMS and parylene are adopted as encapsulants to improve the performance of IPMC [10]. The PDMS layer which was adopted in this research can not only smooth the surface but also be treated as an encapsulation process to improve the performance. There are many applications using IPMC as an actuator. We believe that this paper is the first effort to implement IPMC in a three-dimension deformable mirror area.


Design and fabrication of a large-stroke deformable mirror using a gear-shape ionic-conductive polymer metal composite.

Wei HC, Su GD - Sensors (Basel) (2012)

Schematics of the electro-osmotic migration of hydrated counter-ions within the IPMC network. Black bars and red balls stand for hydrophilic side chains and hydrophobic main chains, respectively.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472876&req=5

f1-sensors-12-11100: Schematics of the electro-osmotic migration of hydrated counter-ions within the IPMC network. Black bars and red balls stand for hydrophilic side chains and hydrophobic main chains, respectively.
Mentions: Ionic polymer-metal composite (IPMC) is a promising alternative material for use in fabricating MEMS-based DMs because of its ability to exhibit large bidirectional actuation with low applied voltage. Figure 1 shows the schematics of the electro-osmotic migration of hydrated counter-ions within the IPMC network. It is a sandwich structure with a layer of Nafion® inside and two layers of metal outside as the electrodes. The chemical formula of Nafion® can be separated into two chains. The hydrophobic main chain forms the backbones to determine the mechanical strength, which is the black bar. The hydrophilic side chain terminated by ionic groups, such as SO3− for cation exchange, is the red ball noted fixed anion. The working principle of IPMC actuation is that when an electric field is applied, hydrated cations move through the cluster networks which are formed by the chains towards the cathode so that the volume expands near the cathode side and contracts near the anode side. As a results the IPMC bends toward the anode. According to the actuation mechanism, the real internal stress inside Nafion® should be symmetric and linear distributed along its thickness [6], which is positive in one layer and is negative in another layer of Nafion®. Traditionally, the IPMC in cantilever beam shape can only generate bending motions, but actuators with the capability of complex deformation are highly desirable in many applications. Pugal et al. [7] presented an electrode patterned IPMC with a twist motion for bionics applications. In recent works [8], we proposed a three-deformational gray box model based on the finite element method (FEM). According to this model, the deformation of IPMC in arbitrary shapes which were confined with different boundaries can be predicted more easily. Therefore, arbitrary deformation can be achieved and pre-designed. In this work, a gear-shape IPMC was designed and demonstrated to deform like a rotationally symmetric, or aspheric, surface. The experimental results agreed well with the simulation data which will be discussed in the latter sections. However, IPMC is known for practical challenges, such as reliability in dry air and the back-relaxation phenomenon. This is mainly due to the actuation mechanism which depends on the movement of hydrated cations inside it. Therefore, the effects of water content on the actuation performance of ionic polymer–metal composites are quite important [9]. Thereafter, encapsulation processes applied to IPMCs are nowadays a critical subject to their practical use. PDMS and parylene are adopted as encapsulants to improve the performance of IPMC [10]. The PDMS layer which was adopted in this research can not only smooth the surface but also be treated as an encapsulation process to improve the performance. There are many applications using IPMC as an actuator. We believe that this paper is the first effort to implement IPMC in a three-dimension deformable mirror area.

Bottom Line: Finally, a gear shaped IPMC actuator was designed and tested.Optical power of the IPMC deformable mirror is experimentally demonstrated to be 17 diopters with two volts.The needed voltage was about two orders lower than conventional silicon deformable mirrors and about one order lower than the liquid lens.

View Article: PubMed Central - PubMed

Affiliation: Graduate Institute of Photonics and Optoelectronics, National Taiwan University, No. 1, Roosevelt Road, Section 4, Taipei 10617, Taiwan. d96941017@ntu.edu.tw

ABSTRACT
Conventional camera modules with image sensors manipulate the focus or zoom by moving lenses. Although motors, such as voice-coil motors, can move the lens sets precisely, large volume, high power consumption, and long moving time are critical issues for motor-type camera modules. A deformable mirror (DM) provides a good opportunity to improve these issues. The DM is a reflective type optical component which can alter the optical power to focus the lights on the two dimensional optical image sensors. It can make the camera system operate rapidly. Ionic polymer metal composite (IPMC) is a promising electro-actuated polymer material that can be used in micromachining devices because of its large deformation with low actuation voltage. We developed a convenient simulation model based on Young's modulus and Poisson's ratio. We divided an ion exchange polymer, also known as Nafion(®), into two virtual layers in the simulation model: one was expansive and the other was contractive, caused by opposite constant surface forces on each surface of the elements. Therefore, the deformation for different IPMC shapes can be described more easily. A standard experiment of voltage vs. tip displacement was used to verify the proposed modeling. Finally, a gear shaped IPMC actuator was designed and tested. Optical power of the IPMC deformable mirror is experimentally demonstrated to be 17 diopters with two volts. The needed voltage was about two orders lower than conventional silicon deformable mirrors and about one order lower than the liquid lens.

No MeSH data available.