This article introduces some analytical and experimental researches on the application of smart materials, especially shape memory alloys (SMAs) and FBG optical fibers to control the shape and vibration of
aerospace structures such as the inflated cylindrical beam and wing. In the first section, the methodology
for adjusting the configuration of inflated cylindrical beam using SMA thin film is presented. The second
one is about the aeroelastic characteristics of Smart Composite Wing fabricated using SMA actuators and a
FBG optical flber sensor.
This paper describes fabrication, evaluation and demonstration of the active laminate proposed by Asanuma. It was made by hot-pressing of an aluminum plate as a high CTE material, a unidirectional CFRP prepreg as a low CTE material and an electric resistance heater, a KFRP prepreg as a low CTE material and an insulator between them, and copper foils as electrodes. In this study, its performances such as shape change as a function of electric-resistance heating temperature were examined and compared with those of a stainless steel type one. As the results, it became clear that 1) the curvature of the active laminate linearly changes only in the fiber direction as a function of temperature between room temperature and its hot pressing temperature by electric resistance heating of carbon fiber in the CFRP layer, and 2) the active laminate was made into complicated forms, that is, a hatch and a stack types, and their actuation performances were successfully demonstrated.
Recently, the authors developed Si3N4, Al2O3 and mullite ceramics with good self-crack-healing abilities. It was shown that the optimized crack-healing condition to get high temperature strength was: 1573K, 1 h, in air, and the healed zone exhibited the same strength as the base material. Using this good healing ability, a new methodology to guarantee the reliability of ceramic components "crack-healing + proof test" was proposed. However, if a crack initiated during service, reliability would be severely impaired. Therefore, if a material can crack-heal during service, and if the healed zone has enough strength at the temperature of healing, it would be very desirable for structural integrity. From the above points of view, a new methodology to guarantee the structural integrity of ceramic components using in-situ crack-healing ability was proposed and the usefulness was discussed using the test results in terms of crack-healing behavior and proof test theory by the authors.
The present paper describes development of active fiber-reinforced metals utilizing their thermal deformation caused by non-uniform distribution or combination of continuous and discontinuous fibers. These types of SiC/Al composites, that is, a laminate of continuous-fiber layer and unreinforced one, that of discontinuous-flber layer and unreinforced one, and that of continuous-fiber layer and discontinuous-flber one were fabricated, and their thermal deformation characteristics were investigated. As the results, all of the composites curve unidirectionally in the flber direction by cooling from the hot pressing temperature. Though the curvature of the composite reinforced on one side decreases by reducing the fiber length, the curvature change during thermal cycles between room temperature and 813 K can be clearly observed even in the case of the discontinuous flber type. The tensile strength of the composite reinforced with continuous flber on one side successfully increases by lamination of the continuous-fiber layer and the discontinuous one. The curvature of this type of active composite can also reproducibly change during the thermal cycles due to the difference of the fiber lengths, and exists between the continuous-flber type and the discontinuous-fiber type ones.
Carbon fiber reinforced (CFRPs) are increasingly commonly used composite materials based on carbon faiber. To evaluate the strength was used the tensile test, bending test and Carpy impact Test. We concluded that EB irradiation reinforced mechanical properties for CFPRP.
Recently, low noise gears without lubrication are required for business machines and robots, because they
are used in open space. The present article provides a new type gear consisting of steel and resin (called
Delrin-100), which has good lubrication characteristics. Our gear has profile shifted steel gear teeth.
Delrin-100 resin is inserted in a grove, which is cut around the gear teeth of the steel gear so as to have
strong gear teeth. Hence, the tooth made of Delrin resin is supported at both sides. This means that only
resin gear tooth contacts to the follower gear tooth, but steel gear tooth does not contact. Production
processes are presented for the gear, and its characteristics are investigated. It is ascertained that the
strength of our gear is greater than that of a plastic gear, and noise of our gear is small in comparison with
plastic gears. The design method is presented, and effects of frictions on the position control are also
In order to realize true regenerative medicine, we have developed a novel technology for the reconstruction
of tissues and organs by utilizing intelligent materials. Cells are cultured on temperature-responive culture
surfaces at 37 °C, and harvested as transplantable cell sheets by reducing temperature. With these cell
sheets we regenerate various kinds of tissues including cornea and heart.
Diamond-Like Carbon and Carbon-Like Nanocomposite electrodes, novel materials in the field of
biosensors, made with different ratio of sp3/sp2 carbon hybridization or doped with elements such as Ni, Si
and W, were characterized electrochemically by cyclic voltammetry and by amperometric measurements
towards hydrogen peroxide. SiCAr1 and SiCNi5% were chosen as sensitive transducers for elaboration of
amperometric glucose biosensors. Immobilization of glucose oxidase was carried out by cross-linking with
glutareldehyde. Measurements were made at a fixed potential + 1.0 V in 40 mM phosphate buffer pH 7.4.
SiCAr1 seems to be more sensitive for glucose (0.6875 μA/mM) then SiCNi5% (0.3654 μA/mM).
Detections limits were respectively 20 μM and 30 μM. Michaelis-Menten constants for the two electrodes
were found around 3 mM. 48% and 79% of the original response for 0.5 mM glucose remained respectively
for both electrodes after 10 days.
A novel colorless and odorless chemical code system was constructed with gas-phase biosensors
(bio-sniffers). Three volatile chemicals, hydrogen peroxide (H2O2), lactate and choline vapors were used
for chemical code. The bio-sniffer devices for these 3 chemicals were constructed by applying catalase,
lactate oxidase and choline oxidase immobilized membrane to a Clark-type oxygen electrode, respectively.
Each bio-sniffer showed high selectivity for their chemical vapor due to the substrate specificity of the
enzyme without crosstalk error. Thus, a 3-bit (8-channel) chemical code was successfully recognized and
distinguished by 3 kinds of the bio-sniffers.
The technology of mercaptide self assembly has previously been used to immobilize molecules onto
epitaxial metals but is not practical for many surfaces. In this study, a designed tag was employed for the
electrochemical immobilization of protein on metals (ECtag). In the case of protein, ECtag can be designed
with a 6-mer amino acid (alfa-amino-1H-imidazole-4-propionic acid) homopeptide. It was employed as an
ECtag ligand and was introduced to a objective protein molecule through genetical process. ECtag forms
co-ordinate bonds with Ni2+ and other divalent metal ions. Protein A (specific affinity protein against igG)
was chosen as a model protein for the immobilization, and was genetically tagged with an ECtag for
immobilization onto a Pt electrode surface through the reduction of ECtag:Ni2+ to ECtag:Ni by the
electrode potential. The immobilization process can be performed through very simple wet-electrochemical
The morphology of water swellable microgel padicles in its aqueous dispersion was studied by
freeze-fracture transmittance electron microscope (FF-TEM) technique. The FF-TEM images showed the
microgel particles were spherical shape and when its concentration was high, the soft gel particles were
packed tightly with the deformation of their shape. The direct observation results support that the
pseudo-plastic flow behavior of the semi-dilute microgel aqueous dispersion, namely, the apparent yield
stress is likely to be due to the closed packing of the soft microgel particles.
For the purpose of reinforce both the bioactivity and mechanical strength of implant material, which
recovers bone defects, bioactive glass is coated on the surface of titanium substrate. To evaluate the
function of bioactibity, immersion test in simulated body fluid is carried out and confirmed the
performance of this material, that the apatite precipitates on the surface of coated glass in two days. This
coating method of bioactive materials is effective for the reinforcement of bioactivity for metal implants.
This paper is concerned with the swimming characteristics and the structure dynamics of diving beetle
legs. Diving beetles are highly adapted for aquatic life. When swimming, all of these insects use their
flattened, paddle-shaped hind legs like oars. Their hind legs have a thick fringe of swimming hairs. Since
diving beetles are excellent swimmers, the swimming behavior is studied with a high speed video camera
system. The structural properties of legs are also studied by an optical microscope and scanning electron
microscope. Some functional principles underlying leg design are revealed.
We study a non-contact support and transportation of flexible steel plate by magnets. The magnetic support
system is essentially unstable because we get only attractive force by the magnet. Electromagnetic force is
controlled so as to keep the plate position at a fixed position. It is difficult to design the control system due to
the strong non-linearity of the force by the electromagnet and the flexibleness of the plate. We employ the
sliding mode control theory to get good quality control.
We have been proposing a magnetic force control method using the inverse magnetostrictive effect of
magnetostrictive materials. With a parallel magnetic circuit consisting of iron yokes and permanent
magnet, the magnetic force exerting on the yoke varies with the mechanical stress applied to the
magnetostrictive material. The characteristics of the magnetic force, such as stress-sensitivity and range of
the variation, are mostly dependent on the material properties of the magnetostrictive material. In this
paper, we investigate the potential of the Galfenol, with high piezomagnetic constant and high saturation
on our proposing method. The comparison of the theoretical and experimental results of magnetic force
clarifies the advantages of the Galfenol.
This paper describes mover materials successfully developed in 2005. They are compressive Sm-Fe alloy
film and its composite multimorph mover devices. The composition dependence of magnetostriction was
studied. The giant magnetostriction (GM) was found from 28 to 34 at%Sm. Furthermore, the largest
compressive value of magnetostriction was 1400 ppm in a SmFe2.2 film prepared at 423 K of substrate
temperature under 0.5 Pa of argon gas sputtering pressure. The high magnetostrictive susceptibility was
also obtained in the bimorph composite GM device constructed with extensive (positive) Tb-Fe and
compressive (negative) Sm-Fe alloys fllms.
The compound TbFe2 and SmFe2 are known to exhibit the largest positive and negative
receptively. Thin fllms prepared by magnetron sputtering process were obtained film structure showed by
Thornton model. The change of this film structure was expected influence of magnetostriction properties.
SmFe alloy thin films were prepared by D.C. magnetron sputtering process at different substrate
temperatures from 323 K to 623 K and at different argon gas pressure of 0.5 and 0.8 Pa. A magnetostriction
of the Sm-Fe alloy film increased with decreasing gas pressure on sputtering. The maximum value of
magnetostriction over 1300 ppm at 1.0 MA/m was found in a Sm-Fe film prepared at 423 K of substrate
temperature below crystallization temperature and at 0.5 Pa of argon gas pressure.
Two types of multi-ferroic actuator/sensor devices. i.e. (1) magnetically driven composite actuator and (2)
multi-functional surface acoustic wave (SAW) sensor by MEMS are presented for intelligent/smart
technologies. The large-scale robust composite actuator (1) is designed to combining the ferromagnetic
property with superelasticity of shape memory alloy (SMA) because it can be driven with high speed as
well as considerably large strain by applying a wireless magnetic field. The composite is reinforced by the
superelastic fiber or lamellar of shape memory alloys (TiNi, CuAlMn) in the ferromagnetic metal(Ni, Fe)
matrix. Secondarily, multi-functionally designed, multi-ferroic senor device of surface acoustic wave
(SAW) is introduced. Piezoelectric LiNbO3(x-y cut) base materials are used. IDT has been produced by
lithography. On the surface part between IDTs, environmentally active material films such as SMA, FSMA,
magnetostrictive alloy etc. are formed by magnetron-sputtering. These results show the possibility of a
new type of multi-functional composite actuator and sensor based on multi-ferroic effect.
Ferromagnetic shape memory alloys have been developed by means of the melt spinning technique. The
alloys are multi-functional materials, which have both the ferromagnetic property and shape memory property.
We have focused our interest on Fe-Mn-Si based alloys, which are nonmagnetic material due to high
manganese content. To improve ferromagnetic function, we have investigated to add rare earth elements
and compared effects of Nd, Sm, Dy, and Ho in detail. The results show that the ferromagnetic functions
can be improved by adding up to 1wt% rare earth elements. The additions worked to shift the Curie pint
upward and to increas the residual saturation magnetization even after heat-treatment. The heat-treatment
has been optimized to obtain the largest saturation magnetization and the perfect shape memory recovery.
A new drive system using shape memory alloy(SMA) wire is introduced in this paper. The system is designed
for a car with the shape recovery force of SMA wire. A loop of SMA wire processed to memorize the straight
line is set around a large pulley and a small one. When the wire around the small pulley is heated partially
with hot vapor, it generates the recovery force at the heated part of the wire and turn to the torque to run
the pulley. A bundle of wires can produce larger torque and it is possible to make SMA heat engine with
the torque. In this study, the factors related to the rotational speed, such as diameter of small pulley, wire
loop number and room temperature, were investigated. Moreover the relationship between wire loop
number and torque too. It shows that the factors plays very important role. The speed of the unmanned car
reached a few kilometers per hour.
Structure and electrical properties of cobalt-containing amorphous hydrogened carbon films were
investigated. Cobalt doped films were prepared by RF discharge of methane gas and DC co-sputtering of
the cobalt target. The structure of the films was examined by transmission electron microscope (TEM) and
Raman spectroscopy. Cobalt atoms form the grain and they are well dispersed in carbon matrix. The
results of Raman spectroscopy show the structure of the carbon is amorphous. But the spectra of the
samples after the heat treatment shows different. D peak position was shifted toward the lower frequency
and this indicated the change of carbon chemical bonding state. Room temperature resitance and
temperature dependence on resistance were also investigated. Resistance at room temperature decreases
drastically with increase of metal concentration. Temperature dependence on resistance with the
concentration variation of the samples indicate , that electrical properties of the samples with strongly
effected by the concentration of embedded cobalt.
We have developed a probe manipulation technique, and fabricated apparatus that can manipulate and
weld fine metal objects of 10 μm to 100 μm. They are caught with a tungsten probe by applying voltages
less than 100 V to the probe. Fine metal objects are welded by contact welding and non-contact welding
using the tungsten probe as an electrode after it was set in place. Contact welding corresponds to resistant
welding, and non-contact welding corresponds to arc welding. Here, we introduce the application of a
smart probe for probe cards. Noble metal alloy particles of 40-75 μm are welded at the top of a
rhenium-tungsten alloy wire of 125 μm in diameter using the apparatus. The composite will be the smart
probe by sharpening the tip. The smart probe will improve the performance of the probe cards. The tip of
the noble metal alloy reduces the contact resistance and will extend the life of the probe card. A cross
section of the welding interface between the wire and the particle is examined by an SEM and an EDX.
Particle assemblage by probe manipulation is a built-up process to fabricate microstructures. We
investigated the probe manipulation method featured by applying voltages to the probe to control the
adhesion force. Two types of probe are fabricated. One is a monopole probe and the other is a dipole probe.
The former is composed of a needle-like metal wire, and the voltage is applied between the probe and the
external electrode like a metal substrate. The latter is composed of a needle-like electrode and a stainless
tube arranged concentrically. The tip of the monopole probe was shaped hemispherically by insulating
resin. The monopole probe can catch fine particles of 10 μm to 100 μm on the metal substrate, while the
monopole probe can catch both conductive particles and dielectric particles without the restriction of
substrates. The particles jump up to the tip of the probe and adhere. The features of the two probes are
Influences of electron beam (EB) irradiation on the impact value for alkali free glass were studied by a
standard Charpy impact test. EB increased impact values of the glass. Evidently, The increased impact
value was mainly due to an increase in the bonding energy for the stronger-bonded metals (Si or
Al)-oxygen atomic pairs in the atomic network structure, as well as a relaxation of the network structure.
Bone mass is increased by adequate exercises. This phenomenon has been mainly explained as chemical
reactions of bone cells in the biochemical field. Because the cells can be considered as structural systems
composed of mechanical components of cytoskeletons and focal adhesions in the view of mechanical
dynamics, the mechanical properties of the cells can affect the response of them to the mechanical
stimulation such as the variation of the bone mass to the stimulation. In this study, mechanical properties of
an osteoblast, which is one of bone cells, were measured experimentally. The tensile and viscoelastic
properties of the cell were measured with tensile and creep tests. The tensile load could be obtained with
measuring the deflection of a micropipette, whose spring constant was calibrated after each test. As a result,
the relationship between the tensile load and the elongation of the cell was obtained. In addition to the
tensile test, the increase of the elongation of the cell was measured keeping the tensile load as constant in
the creep test. Using these experimental results, a three-element model of the cell for viscoelasticity was
introduced and the value of each element was identified.
A metallic closed cellular material for smart materials has been fabricated by sintering of metal coated
powder particles. Powder particles materials coated with nickel-phosphorus alloy layers using electro-less
plating were pressed into pellets (green pellets) and sintered in vacuum at high temperature using an
electric furnace or a spark plasma sintering system. Then a metallic closed cellular material containing
organic material was then constructed. The cross-sections of the specimens were observed using the
scanning electron microscope. The compressive and damping tests were carried out to measure the
mechanical property of this material. The results of the compressive tests show that this metallic closed
cellular material has a long plateau region and high-energy absorption. In addition, the specimens sintered
at different conditions have different mechanical properties. The compressive strength would increase due
to the increasing of cell wall thickness. The results of the damping tests show that the internal friction of
this material is same as that of pure aluminum.
Due to the nonlinearity, time-delay of magneto-rheological (MR) suspension system, application of linear
feedback control strategy is limited. Therefore, a human-simulation intelligent control (HSIC) for MR
suspension is proposed and studied. To determine the time-delay magnitude of MR damper, an
experimental apparatus is founded and the response time is tested for various operating conditions. The
results show that the response time of MR damper is about 30 ms that cannot be ignored in real time
control. A hybrid Taguchi genetic algorithm (HTGA) is adopted to tune the parameters of the HSIC
controller. To verify the feasibility of our approach, road test are carried out. The results show that after
some threshold parameters are optimized by HTGA, HSIC can achieve better ride comfort and stability
compared to passive suspension.
Since magneto-rheological (MR) suspension has nonlinearity and uncertainty, a new adaptive fuzzy
control strategy using a hybrid Taguchi genetic algorithm (HTGA) is proposed to improve ride quality. The
controller consists of two control loops. The inner open loop controls a nonlinear MR damper to achieve
tracking of a desired force. The outer loop implements a fuzzy logic controller (FLC) using HTGA. The
HTGA is used to tune the membership functions and fuzzy control rules of FLC with initial skyhook
control rules. To verify the control performance, FLC based on HTGA for semi-active suspension system
is simulated. The simulation results show that FLC based on HTGA can achieve smaller acceleration root
mean square (RMS) than simple FLC and better ride quality compared with passive suspension under
In this paper, the Eyring constitutive model parameters have been identified via minimization of the error
function defined as error sum between shear stresses from experimental tests in laboratory of Chongqing
University and shear stresses depicted the Eyring constitutive model. Authors have theoretically set up
flow control equations for magneto-rheological (MR) fluids in annular channels using the Eyring
constitutive model and N-S equations in hydrodynamics. The velocity profiles of MR fluids through
annular channel are obtained by means of flow control equations mentioned above. In accordance with
piston velocity and annular channel geometrical parameters of MR fluid shock absorber, MR shock
absorber performances have been predicated by means of analytical methodology developed in this paper.
In the light of technical requirements of front suspension of Chanan star minibus, a MR fluid shock
absorber, which is designed and fabricated in Chongqing University according to design method presented
in this paper, has tested by electro-hydraulic servo vibrator and its control system in National Center for
Test and Supervision of Coach Quality. The experimental results reveal that the analytical methodology
and design theory are reasonable.
This paper describes the aging process of the interfacial instability of magnetic fluids subjected to
vertically oriented magnetic field. The interfacial instabilities of two kinds of magnetic fluids were
observed for a long time. The time series of the interfacial instability aging (spike pattern transition) of
magnetic fluids was examined by the photographic recording methods. It was found that the interfacial
spike pattern of magnetic fluids changes with time dramatically.
Magnetorheological (MR) fluids can vary their rheological characteristics by applying magnetic field
strength and have been applied to various kinds of devices. In this study, an MR fluid was applied to an
engine mount. This MR engine mount can not only mount an engine to insult its vibration, but also absorb
impact force applied to drivers when a car collides in an accident. As an engine is the heaviest component
of a car, the impact force can be reduced by controlling the damping force of the engine with the MR
engine mount. In order to design the MR engine mount, we measured the typical characteristics of the MR
fluid, as which we obtained the relationship of the shear stress to the flow rate, the magnetic flux density
and the gap length of the MR fluid flowing, and the response time to the magnetic flux density. Using
these experimental results, the MR engine mount was designed to satisfy the desired controllable range of
the damping force.
A new-type tire is presented, in which there is no air leakage when nails break the tire. The broken part is
repaired automatically by its self-repairing mechanism. The self-repairing sealant layer is consisting of two
rubber sheets with lattices inside. Polymer particles are inserted in the lattices in the sealant. Coolant fluid
diluted with water is inserted in the polymers umiformly, and so the polymer particles expand with water diluted
coolant fluid, and become gel. Hence, they stop air leakages in the tire. The sealant is pasted to the inside wall of
the tire. A method of making the sealant is developed, and vibration characteristics of the tire with the sealant
This paper discusses the development of a parallel distributed structural health monitoring system based
on the wireless sensor network and multi-agent system for large scale engineering structures. The
distributed smart wireless sensor network node is researched first. Then the multi-agent definition in the
structural health monitoring system and their cooperation structure is researched. A bolt and load
monitoring system is developed to realize a small multi-agent based health monitoring system.
A spatial resolution of real-time bioradiography system was closely measured using PDMS (polydimethyl siloxane) microfluidic chips with microchannels down to 20um wide. We measured the spatial resolution by comparing line width of a chemiluminescence image and a beta-ray image. Both images were obtained using identical microchannel. Using our method, a spatial resolution can be measured within an equal condition to actual observation. In addition, the spatial resolution was improved upto 20um FWHM(Full Width at Half Maximum), which is 50 times better than that of conventional method. Owing this method, we experimentally confirmed that b-ray scattering degrades the spatial resolution of the β-ray image.
In this paper, Empirical Mode Decomposition (EMD) is employed to eliminate noises existing in
experimentally acquired ultrasonic guided Lamb wave signals. The detailed procedures are provided and
several examples involving both narrowband and wideband signals are given to show the validity of the
proposed de-noising method. Comparisons are made with the results obtained by the well-known Wavelet
method. It is found that both EMD-based and Wavelet-based de-noising methods can yield acceptable
results. It is also found that EMD-based de-noising method can separate noises from noise-polluted signals
more efficiently due to its adaptive nature in the de-noising process, and that less empirical information is
required as compared with the Wavelet-based de-noising method. Based on the results reported herein, one
may conclude that EMD-based de-nosing method can be effectively used to get a clear and significant
response signal, an important step in the area of structural health monitoring. Further research should be
made to establish a reliable criterion for separating a useful IMF from noise components in general cases.
Active, semi-passive and passive noise isolations of a plate bonded with piezoelectric elements were
studied and their effectiveness is compared. The noise is generated by a loudspeaker inside a box and
transmitted to the outside through the plate. The frequency of the noise was swept around the first
resonance mode of the plate. The results show that the damping effect at the first resonance mode reaches
7.4dB with semi-passive technique, 13.5dB with active technique and 8.2dB with passive technique. The
influence of sweeping speed on the control performance of each approach was investigated, and a large
decrease of performance was observed for semi-passive control (70% of decrease) at the sweeping speed
of 200Hz/sec. A decrease of 30% is observed in case of active control, whereas there is almost no decrease
of performance with passive technique. Increasing the excitation level leads to non-linear behavior of the
plate inducing a much lower damping. The influence of excitation level on the control performance of
three approaches was investigated. The results show that all these three techniques are easily affected by
For high voltages, large hystereses are usually observed in multi-stack actuators. To cancel it, either
hysteresis modeling or closed loop system can be used. To overcome the limitations of both techniques,
we present here an application of the correlation of the strain and polarization to build a self-sensing
hysteresis cancellation. The advantage of this technique is to remain efficient for various voltage profiles
and don't require additional sensor.
This work concerns the study of bone regeneration between two parts of a cut bone that occurs while the
elongation of such bone. In the actuation that can move one part of the bone with respect to the other the
displacement will be discontinuous consisting of very small steps to maintain a daily given very small gap
between the two bone parts. The forces required are very weak because they only stretch the tendons that
are elongated in few displacements. The actuator described in this paper fulfils given specifications and is
of few centimetres dimensions. It is a piezoelectric actuator so that the use of magnetic resonant imagery
could be possible even if the patient wears such actuator. The principle of displacement is inchworm and
its total range is only determined by the length of the rotor (moving part). A prototype has already been
achieved. This paper deals with the design and the characterization of this actuator.
Some dielectric elastomers produce large electric-field-induced strains that can be used for
electromechanical actuation. When an electric field E is applied on an electroactive polymer film
electroded on both sides, the film is subjected to a stress T due to the electrostatic force (Maxwell stress)
and this causes it to deform, producing a strain in the plane perpendicular to the applied field. We have
measured the transverse strain responses of silicone (Dow Corning HS III) Maxwell stress actuator
samples of different sizes over a wide displacement range and a frequency range from DC up to 100 Hz.
The static and dynamic strain responses of the materials to a variety of driving electric flelds such as step
fields, AC fields and DC bias fields have been measured as functions of amplitude and frequency. The
effect of a mechanical tensile pre-load on the transverse strain has also been investigated. A pre-load
initially causes an increase in the strain but the strain decreases when larger values of pre-load are applied.
Numerical finite element simulations of the material using the commercial software package ANSYS and
suitable models of hyperelasticity provide good agreement with most of our observations on the electric
field and pre-load dependencies of the transverse strain.
This paper reports the development of a wrist-watch type wearable system for mental stress evaluation. A
pulse sensor has been developed using the PVDF film for heart beat intervals detection. Visualization of
mental stress using a modified Symmetrized Dot Patterns (SDP) method has been proposed. The system is
testified through mental stress experiments.