Sang Yeol Yang

Paper Actuators Made with Cellulose and Hybrid Materials

Recently, cellulose has been re-discovered as a smart material that can be used as sensor and actuator materials, which is termed electro-active paper (EAPap). This paper reports recent advances in paper actuators made with cellulose and hybrid materials such as multi-walled carbon nanotubes, conducting polymers and ionic liquids. Two distinct actuator principles in EAPap actuators are demonstrated: piezoelectric effect and ion migration effect in cellulose. Piezoelectricity of cellulose EAPap is quite comparable with other piezoelectric polymers. But, it is biodegradable, biocompatible, mechanically strong and thermally stable. To enhance ion migration effect in the cellulose, polypyrrole conducting polymer and ionic liquids were nanocoated on the cellulose film. This hybrid cellulose EAPap nanocomposite exhibits durable bending actuation in an ambient humidity and temperature condition. Fabrication, characteristics and performance of the cellulose EAPap and its hybrid EAPap materials are illustrated. Also, its possibility for remotely microwave-driven paper actuator is demonstrated.

Wirelessly driven electro-active paper actuator made with cellulose-polypyrrole-ionic liquid and dipole rectenna

This paper reports a wirelessly driven electro-active paper actuator that consists of a dipole rectenna array, a power control circuit and two cellulose–polypyrrole–ionic liquid (CPIL) electro-active paper actuators. The CPIL nanocomposite actuator was fabricated by incorporating nanoscaled PPy onto cellulose by an in situ polymerization technique, which was followed by activation in a room temperature ionic liquid. The CPIL actuator shows its maximum bending displacement of 10 mm at an ambient humidity condition with 30 mW electrical power consumption. The CPIL actuator is very stable in its actuator performance. The dipole rectenna array receives microwaves and converts them to dc power so as to wirelessly supply power to the actuators. Three flexible dipole rectenna arrays are designed, manufactured and characterized. The rectenna array that has nine rectenna elements generates the maximum power of 75 mW. This power was used to successfully activate the two CPIL actuators and the control circuit. Detailed fabrication and characterization of the CPIL actuator and the dipole rectenna array as well as the control circuit are explained.

Actuator, sensor and MEMS devices based on regenerated cellulose

In our early work, cellulose has been discovered as a smart material that can be used as sensors, actuators and smart devices. This newly discovered material is described as electro-active paper (EAPap) and has many advantageous properties: lightweight, flexible, dryness, biodegradable, easy to chemically modify, cheapness and abundance. The actuation principle of cellulose EAPap is based on a combination of piezoelectric and ion-migration effect. This paper reports the fabrication of various micro-patterns and structures, such as rectifying antenna and inter-digital transducer on regenerated cellulose film by adopting a micro-transfer printing technique. Fabrication steps are briefly discussed herein and performance of the actuators was evaluated by means of a tip displacement test. Further, potential application of cellulose as humidity sensor was demonstrated by measuring the impedance change on the inter-digital transducer on cellulose film at different humidity levels.

Remotely powered and controlled EAPap actuator by amplitude modulated microwaves

This paper reports on a remotely powered and controlled Electro-Active Paper (EAPap) actuator without onboard controller using amplitude modulated microwaves. A rectenna is a key element for microwave power transmission that converts microwaves into dc power through coupling and rectification. In this study, the concept of a remotely controlled and powered EAPap actuator is proposed by means of modulating microwaves with a control signal and demodulating it through the rectenna rectification. This concept is applied to a robust EAPap actuator, namely cellulose?polypyrrole?ionic liquid (CPIL) EAPap. Details of fabrication and characterization of the rectenna and the CPIL-EAPap actuator are explained. Also, the charge accumulation problem of the actuator is explained and resolved by connecting an additional resistor. Since this idea can eliminate the onboard controller by supplying the operating signal through modulation, a compact and lightweight actuator can be achieved, which is useful for biomimetic robots and remotely driven actuators.

Electrical and Electromechanical Properties of Cellulose-Polypyrrole-Ionic Liquid Nanocomposite: Effect of Polymerization Time

The effect of polymerization time on ionic liquid (IL) nanocoating onto polypyrrole (PPy) adsorbed cellulose and its influence on electrical and electromechanical properties were investigated. Cellulose-PPy-IL (CPIL) nanocomposites were fabricated by polymerization-induced adsorption process followed by subsequent activation in 1-butyl-3-methyimidazolium chloride IL solution. Fourier transform-IR spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy analysis showed successful preparation of the CPIL nanocomposites. Results revealed that CPIL nanocomposites can be utilized to develop a highly durable biomimetic actuators working in ambient condition. Preparation, characterization, and performance test of the actuators are explained.

Cellulose electro-active paper: actuator, sensor and beyond

Recently, cellulose has been discovered as a smart material that can be used as sensors and actuators. This newly discovered material is termed as electro-active paper (EAPap) that has merits in terms of lightweight, flexible, dryness, biodegradable, biocompatible, easy to chemically modify, cheap and abundance. The actuation principle of cellulose EAPap bending actuator is known to be a combination of piezoelectric effect and ion migration effect. This paper presents further investigation of cellulose EAPap for its possibilities in biomimetic actuator, sensor, MEMS, acoustic devices and others. Biomimetic actuator is made with cellulose EAPap by fabricating rectifying antenna (rectenna) array on it. Cellulose EAPap material is customized to satisfy the material requirement for actuators and other devices. The material improvement all about cellulose EAPap is introduced. To fabricate the rectenna array, micro patterning of metallic layer in conjunction with Schottky diode fabrication on the cellulose was made. The Schottky diode fabrication allows possibility of thin film transistor fabricated on a cellulose paper. Microwave power transmission is demonstrated by using rectenna arrays, which can be used for many applications. Some of the device fabrication along with brief demonstrations is illustrated.

Flexible Patch Rectennas for Wireless Actuation of Cellulose Electro-active Paper Actuator

This paper reports a flexible patch rectenna for wireless actuation of cellulose electro-active paper actuator (EAPap). The patch rectenna consists of rectifying circuit layer and ground layer, which converts microwave to dc power so as to wirelessly supply the power to the actuator. Patch rectennas are designed with different slot length at the ground layer. The fabricated devices are characterized depending on different substrates and polarization angles. The EAPap integrated with the patch rectenna is actuated by the microwave power. Detailed fabrication, characterization and demonstration of the integrated rectenna-EAPap actuator are explained.

Design and applications of flexible dipole rectenna for smart actuators and devices

Flexible dipole rectenna devices appeared to be attractive for this study because of the adaptability on complex structures; possibility for higher power density features, and ability of coupling. In this paper, design concepts and results of various flexible dipole rectennas will be discussed including their efficiencies. Using the result, some applications of the system will also be addressed. A typical output of a flexible dipole rectenna array produced up to 70 VDC and 300 mA with a 200W amplifier. The irradiance of the microwave power is measured as 20 - 200 mW/cm2 at the distance of 130 cm from the horn. In this research, a 4 x 5 flexible rectenna array was used for actuation of a propeller of MAV which is required approximately 3W as an input power. The design concept of various rectennas that depends on the requirements of input for propellers/actuators in a vehicle is discussed.

Microwave power transmission of flexible dipole rectenna for smart sensors and devices

There are several potential candidates for energy transmission technologies suitable for smart actuators and sensors. Smart materials have actively been developed in previous decades in order to sense environmental changes or to actuate proper devices, but their applications as a practical system are limited due to the requirements of hardwire circuits and power supply. These limiting factors have been key challenges to overcome for practical applications of smart materials. This paper presents the design, fabrication and test of flexible dipole rectenna arrays for wireless microwave power transmission. Low voltage/high current rectenna array is designed and the maximum current of 980 mA and the maximum power of 7.2 W are observed. Since this rectenna array is sensitive to the polarization angle, a polarization-free rectenna array is designed. Output voltage, current, power, efficiency and the influence of polarization angle as well as incidence angle on the performance of rectenna array are investigate.

Investigation of coplanar strip dipole rectenna elements for microwavepower transmission: simulation and experiment

The performance of dipole rectenna for microwave power transmission is very critical to the size and configuration of the dipole rectenna. Thus, it is important to verify the performance of dipole rectenna by comparing its performance in terms of simulation and experiment. This paper reports an experimental and computational investigation of coplanar strip (CPS) dipole rectenna for microwave power transmission. Rectenna consists of an antenna and a rectifier that involves a Schottky diode. CPS dipole antenna and rectenna are simulated using commercial software, so called Ansofts HFSS and Designer. CPS dipole antenna as well as rectenna is fabricated on a copper coated polyimide substrate using an etching process. The characteristics of CPS dipole antenna are tested by using a pulse analyzer and spectrum analyzer under a 1.2 W microwave power incidence. Comparison of the simulation results with the experiments is made. The verified simulation approach for the CPS dipole rectenna will bring an effective design approach of rectennas for microwave power transmission.