Semiconducting ZnO layer chemically grown on regenerated cellulose and its flexible paper transistor were studied. ZnO
layer-cellulose composite was prepared by a simple chemical reaction process which included alkaline hydrolysis at low
temperature lower than 100 °C and used wet regenerated cellulose as a hydrophilic substrate. By increasing the
concentration of ZnO seeding layer on cellulose, the area of ZnO cluster also increases. In the low concentration
conditions from 20 mM to 50 mM, it is observed that the average size of ZnO nanorods increases as the seeding
concentration increases. However, flower-shaped ZnO structure is observed in higher concentration over 50 mM due to
clustering effect during the growth of ZnO rods. Thin ZnO layer composed of nano-rods seemed to be grown well on
regenerated cellulose and layer thickness of ZnO was well controlled by reaction time. Structural data of as grown
ZnO/cellulose provides the crystal orientation-limited growth mechanism of ZnO nano-rod, which can be controlled by
the reaction time of chemical process. Using conventional lift-off process, thin ZnO layer based transistor was fabricated
by forming source/drain as well as gate electrode. More detailed ZnO-cellulose based transistor is discussed.
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 Ansoft's 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
This paper reports a remotely-driven electro-active paper (EAPap) actuator by modulated microwaves. So far we
have demonstrated a remotely driven EAPap actuator by means of rectenna and control circuit. The rectenna consists of
dipole antenna and rectifying circuit, which converts microwave to dc power. Once microwaves are incident on the
dipole rectenna, it converts microwaves into a dc power and the control circuit feeds the power to the EAPap actuator by
alternating it so as to produce a bending motion of the EAPap actuator. However, due to the power consumption of the
control circuit, the remotely-driven actuator system requires more dc power to activate the control circuit. Thus, we
propose a remotely-driven EAPap actuator that does not require the control circuit. Instead of the control circuit,
microwaves are modulated with the control signal, and by rectifying the modulated microwaves with the rectenna, the
control signal can be regenerated for activating the EAPap actuator. Detailed modulated microwave, rectenna design,
fabrication, characterization and the actuation of rectenna-EAPap by modulated microwave are explained.
A cellulose solution was prepared by dissolving cotton pulp in LiCl/ N,N-Dimethylacetamide (DMAc) solution, and
functionalized multi-walled carbon nanotubes (MWCNTs) were reacted with N, N-Carbonyldiimidazoles to obtain
MWCNTs-imidazolides. By acylation of cellulose with MWCNTs-imidazolides, MWCNTs were covalently bonded
with cellulose chains. Using the product, MWCNTs covalently bonded cellulose composite (M/C) composite was
fabricated with mechanical stretching to align MWCNTs with cellulose. Finally, inter-digital comb electrode was formed
on the composite via lift-off process. Chemo-electrical properties of the M/C composite in response of absorption of the
volatile vapors corresponding to 1-propanol, 1-butanol, methanol and ethanol were investigated. Due to sensitive and
reversible expansion/contraction of the M/C composite matrix in response to absorption of each analyte, the M/C
composite showed fast and reversible change in chemo-electrical property. The ranking of relative resistance response of
the composite was methanol < ethanol < 1-propanol < 1-butanol.
For many sensors, bio-sensors, and probes, it is critical to provide a suitable power
source nano or micro scale feature size, flexible structure, and physiologically
friendly materials. In this study, rectenna array was considered as a power source
using microwave that transmits through the tissues of humans or animals. In
addition, biological effects on humans and animals are discussed as well.
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.
We studied the wireless power transmission capabilities of microwave through
human skin-tissue. Microwave transmission through simulated human skins was
tested with rectenna array as a power receiver located under the simulated human
skin tissue. Most of transplanted medical devices and sensors require power to
operate autonomously but currently by imbedded battery. Wireless power
transmission alleviates the needs of imbedded power source and hard-wire power
network. We used human skin-like materials, such as various polyurethanes and
pork skin, under X-band microwave exposure. Transmission rate through various
polyurethanes under the threshold limit value (TLV) and dielectric constant was
measured in this experiment. It is also critical to measure specific absorption rates
(SAR) of polyurethanes and transmission rates through polyurethanes as well as
pork skin. This paper presents power transmission rates under varying thickness of
polyurethanes, and effectiveness and efficiency of rectennas under the TLV of
microwave power. In addition, we will discuss milimeter wave thermograph and
hazards the absorption characteristics of human skin under 8-13 GHz using the
results of polyurethanes and pork skin.
Significant amount of pentacene can be dissolved in N-methylpyrrolidone (NMP) solvent. The solution color
changed from deep purple to intense yellow. As the dissolution time increased, UV-visible absorption increased and
several new absorption peaks were appeared. The solution was mixed with poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate) (PEDOT:PSS). PEDOT:PSS or PEDOT:PSS doped with pentacene was
spin-coated to the Al coated substrate. Au-electrode was fabricated on top of the semiconductor. Three-layered Schottkys
diode comprised of Al, PEDOT:PSS or PEDOT:PSS-pentacene, and Au with thickness of 150nm, 420nm, and 1200nm,
respectively were fabricated. The current densities of 4.8μA/cm2 at 2.5MV/m and 440μA/cm2 at 1.9MV/m were obtained
for the Au/PEDOT:PSS/Al and Au/PEDOT:PSS-pentacene (3.2 mg)/Al Schottky diodes, respectively. The current
density of Schottky diode enhanced about two order of magnitude by doping pentacene to PEDOT:PSS.
There are several potential candidate energy harvesting technologies for smart actuators and
devices, such as space vehicles, high altitude airships, MAVs (Micro-Aero Vehicles), and
smart robots. Smart material actuators have actively been developed during the last couples of
decades for controlling flow-fields over aircraft wings, shape changes for step-motions, or discrete motion of actuators, but their applications as a practical system are limited due to hardwire circuits and high voltage requirements. The wired power configuration provides lack of maneuverability of the system, especially it is not possible for micro aerial vehicles (MAVs), space vehicles, and airship applications. In addition, the hard wiring may not be a suitable
solution due to the network complexity. Moreover, the weight increase may be attributed to the a wired network, the complex gate switching of power and control networks needed, and the
interdependency of power and control routines needed.
Flexible dipole rectenna devices appeared to be attractive for various applications because of
the adaptability on complex structures; possibility for higher power density features, and ability
of high coupling efficiency. In this paper, design concepts and results for various flexible dipole
rectennas as well as effects of incident angle of microwave energy on rectennas will be discussed including their efficiencies. The discussion will also include the effects of distance
between microwave source and rectennas on airship vehicles. Using the result, some applications of the system will also be addressed.
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.
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.
This paper deals with micro-patterning process of EAPap (Electro-Active Paper) for achieving biodegradable and flexible MEMS. EAPap has been known as an active material with an interesting actuation phenomenon of papers. Such active materials were made by depositing very thin electrodes on both sides of cellulose paper strip. When an electric field is applied to the paper strip, a large displacement was produced. This active material has merits in terms of large strain, low voltage, low power consumption, dryness, cheap and biodegradable nature. This material can be designed in such a way that its advantages can be optimized. With these advantages and possibility, this material is attractive for biodegradable and flexible MEMS. This paper reports a micro-patterning process on flexible EAPap material. Key issues in this biodegradable MEMS fabrication with EAPap are 1) the preparation of EAPap material for micro scale fabrication, 2) micro patterning possibility on EAPap and 3) functional capabilities of sensing and actuation. This paper will introduce a micro contact printing for the micro patterning process on the EAPap flexible membrane.