The authors of this article are characterised by having a background within robotics technology, and have within the last 2-3 years moved into a material & process dominated environment. The authors are among other things responsible within LEGO Company; an internationally known toy developer and producer, for identification, prioritisation and procurement of new technological opportunities within materials, processes and devices providing new functionalities for the LEGO product.

Transducing materials are being used in many aspects of our daily life serving as actuators, sensors, displays, communications and other components of commercial mechanisms. At JPL, such materials are being used to enable novel space and terrestrial applications. This effort involves mostly the use of piezoelectric, electroactive polymers (EAP), and shape memory alloys (SMA). The piezoelectric based devices and mechanisms that were developed include ultrasonic motors, piezopump, ultrasonic/sonic driller/corer (USDC), and ferrosource. Further, the electroactive polymers were used to demonstrate a gripper, wiper, lifter and haptic interfaces. The research and develop tasks consists analytical modeling, experimental corroboration, material characterization as well as device and mechanisms design, construction and demonstration. This effort is multidisciplinary requiring expertise that is complemented through international cooperation. The research team activity will be reviewed in this paper.

The Electrostatic Self-Assembly (ESA) method is a new process that has been successfully tested for the deposition of coatings on glass, silicon, polymer or metallic substrates. This technique allows to control the individual layer composition and the thickness of the coatings on the nanometer scale and has been already proved on substrates with different sizes and shapes such as prisms, curve lens or fibers. The molecular species of the nanolayered structures and the long-range physical order of the layers determine the resulting coating properties. Combining the proper materials it is possible to build up sensitive coatings onto optical fibers for the measurement of humidity, harmful gases, volatile organic compounds or pH. These sensitive films can have thicknesses from 1 nanometer to 1 micron. Here, a review of the different optical fiber sensors fabricated up-to-date using the ESA process is presented. The promising results obtained as well as the new possibilities opened by the synthesis of the new multilayered materials using the ESA method are also studied.

Damping of axial and bending mode vibrations in giant magnetoelastic polycrystalline TbDy alloys was studied at cryogenic temperatures. All specimens of TbDy were arc-melted in the proper composition ratio and dropped into a chilled copper mold. Additional treatments consisted of cold plane-rolling to induce crystallographic texture and then heat-treating to relieve internal stress. Mechanical hysteretic losses were measured at various strains, frequencies, and loading configurations down to 77 K. Both as-cast and textured polycrystalline TbDy samples were tested along with an aluminum specimen for comparison. Loss factors at multiple natural vibration frequencies of the samples were measured for axial modes. Larger damping rates were measured for axial mode vibrations than for bending mode vibrations, possibly reflecting the larger specimen volume contributing to magnetoelastic damping. At LN₂ temperatures TbDy materials demonstrated η > 0.05 at 0.01 Hz and η > 0.1 at higher frequencies from 0.6-1.5 kHz.

In recent years, pre-strained TiNi shape memory alloys (SMA) have been used for fabricating smart structure with carbon fibers reinforced plastics (CFRP). However, since the curing temperature of CFRP is higher than the reverse transformation temperatures of TiNi SMA, special fixture jigs have to be used for keeping the pre-strain during fabrication, which restricted its practical application. We have developed a new method to control the transformation temperatures of SMA by proper thermo-mechanical treatments and composition adjustment, which is suitable to fabricate SMA/CFRP smart composite with a curing temperature of 130C. Furthermore, we tried to develop a new fabrication technique which is also suitable to fabricate SMA/CFRP smart composite with a curing temperature of 180C. It was found that by using cold drawn ultra-thin TiNi wires, TiNi/CFRP composites with a curing temperature of 180C could be fabricated without special fixture jigs. The damage suppression effect by embedded ultra-thin wires in the smart composite was confirmed.

Ti50Ni50-xCux fine fibers were successfully developed by the arc-melted rapid-solidification method.It has been very difficult to do the conventional melt-work processing from the bulk material of this alloy to very fine fiber because of the brittleness from metallic compounds especially in the range of Cu⩾8 at%. The fibers showed good shape memroy effect. As Cu content increased, the temperature hysteresis of recovery strain-temperature curves as well as DSC curves became smaller and the tensile strength showed more than 1000MPa in Ti50Ni40Cu10 at% fiber. Therefore, the developed rapid-solidified, thermoelastic fiber fiber actuator/sensor materials have high potentiality of applications for micro-machines and the fillers of smart composites.

The clamant need for field controlled high strain actuator materials in a multitude of emerging smart materials applications has lead to extensive studies over a very wide range of materials systems from ultra soft elastomers to exceedingly stiff martensitic metals. The capabilities which have been achieved and the basic strain mechanisms exploited to achieve high controlled deformation will be briefly reviewed. The focus of the talk will be upon the importance of ferroic systems, where incipient or full spontaneous ordering permits the achievement of strain levels which would otherwise be impossible in such stiff matrices. The struggle to discipline and control spontaneous ordering so as to achieve well controlled anhysteretic response will be discussed, drawing on the examples of the electron irradiation modified polyvinylidene fluoride:trifluoroethylene copolymer and the high strain high coupling response in the single crystal lead zinc niobate: lead titanate (PZN:PT) perovskites. It is interesting to note the common theme of engineering instability in domain and/or sub domain structures important in these two grossly dissimilar material systems and the manner in which this is carried forward in other ferroics. The final important question to be discussed is where these considerations lead for the design of the next generation of improved high strain actuator materials.

This paper describes and demonstrates a technology for making distributed sensors with spatial filtering properties. The concept is based on a porous electrode with variable porosity, which allows to tailor the effective piezoelectric coefficients in two dimensions. Two applications are considered: (i) a modal filter for a cantilever beam, and (ii) a volume displacement sensor for a simply supported plate.

In an attempt to develop piezoelectric sensor and actuator for smart board, complex piezoelectric fibers with metal core were fabricated by both hydrothermal method and extrusion method. The insertion of metal core was significant in view that the fragility of ceramics can be overcome and electrodes are not required in the use as sensor and actuator. In order to evaluate the sensor and actuator abilities of these new-type fibers, a cantilever structure was constructed by embedding them into the surface of CFRP composite board. As a result of vibration test of this CFRP board by electromagnetic vibrator, it was found that the fiber has an obvious sensor function, since electric charge was output from the fiber in proportion to the vibration amplitude. On the contrary, it is also evident that the fiber can function as actuator, since the CFRP board was vibrated by applying an AC voltage between the metal core and CFRP matrix. By connecting the shunt circuit with the piezoelectricity fiber, it was proven that the vibration in the smart board could be suppressed.

A combination of the preparation technique for ferroelectric films such as lead zirconate titanate (PZT) and the micromachining of Si is considered to be an effective way to fabricate piezoelectric microdevices like microactuators called a microelectromechanical system (MEMS). However, the amount of the displacement and force of PZT thin films is not sufficient in some applications of microactuators. To achieve the property of large displacement, increase of the film thickness or improvement of the piezoelectric property is required. One of the techniques to improve the ferroelectric and piezoelectric properties is assumed to be the arrangement of the polarization direction using a texture control process. We successfully preparaed the (100) and (111) dominant oriented Pb(Zr_1-xTi_x)O₃ thin films using a chemical solution deposition (CSD) process. On the other hand, an arc-discharged reactive ion-plating (ADRIP) method is one of the candidates to fabricate the thick PZT films because of high deposition rate such as 3 μm/h. In this work, the texture-controlled PZT thin and thick films deposited onto Pt/Ti/SiO₂/Si substrates were prepared using CSD or ADRIP process for actuator applications. In the case of ADRIP process, (100) and (111) dominant oriented PZT thick films was formed onto CSD derived and texture controlled PZT thin film layer.

The contribution describes the effects of both van der Waals and repulsive electrostatic forces on the function of micron-sized contractile units of the human muscles - sarcomere. The first step of the contraction of 1-2 nm is assumed to be phase transition of the internal structure of actin filaments. The most significant second step of contraction is interpreted as calcium induced phase transition of the lattice of colloid-sized myosin heads, which results in relative actin-myosin sliding of about 6-7 nm. The third step of the contraction of 1-2 nm seems to be the result of the classical myosin heads swinging. The model should provide the engineer and physicist with a simple analogy to technical actuators of high performance.

Cellular space-charge electrets have emerged as a new class of materials for electromechanical devices, offering a huge potential for applications in noise reduction or cancellation, non-intrusive surveillance, advanced monitoring in health care, as well as in non-destructive testing. Here we report on piezoelectric responses in sandwich structures of two dielectric films separated by an air-gap of a few micrometer thickness. The sandwich structure is charged by dielectric barrier microdischarges within the air-gap. Wide ranging similarities to ferroelectric materials are demonstrated, like hysteresis loops in the dielectric and electromechanical properties versus applied voltage. Applications may emerge in electrostatic microelectromechanical devices.

Macrobending in optical fibers causes reduction in the amplitude of the light signal that passes through them. But in this manuscript we present details of using such a macrobend single mode optical fiber in the Mach-Zehnder interferometer configuration to measure displacement or force.

Optics offers great possibilities for the design of cheap force sensors. One of the applications where these sensors are needed, is a computer pen. There, the force sensor is used to measure the contact forces between the pen tip and the paper. The optical tri-axial force sensor presented in this paper is designed for this purpose. The sensor is based on a flexible structure, which converts the force into a displacement. This displacement is measured optically, with a LED, a photodiode and a moving plate between these two components. Tests show that this simple measuring principle reaches a resolution of 60nm and a linearity of 1% in the range of 500μm. Based on these experiments, a mechanical structure is designed. Special attention is spent to get an equal stiffness and, therefore, an equal sensitivity in all directions. In addition each axis is provided with an emergency stop, to protect the sensor against overloading. The design results in a sensor with the size of 8.4mm x 8.4mm x 44.2mm. After production and assembly, this sensor is tested. It has a resolution of 0.01N, a sensitivity of 40mV/N and a linearity of 2%. Moreover, the sensor is insensitive to temperature variations, due to an extra dummy pair of LED and photodiode.

During construction of extra high structures such as a skyscraper or a main tower of a long bridge, just a slight wind can generate low frequency vibration, and the maximum displacement at the top of structure can increase up to a few meters. Occurrence of low frequency vibration causes a fear of operators and it deteriorates awfully safeness. The purpose of this paper is a control of low frequency vibration above-mentioned with a development of small-lightweight actuator which can control a big displacement and that of control system which guarantees a stable control. As a first step, beam structure is estimated. Design of modal sensor using PVDF film sensor is explained. For an actuator, SMA/CFRP hybrid moment actuator is used. This actuator has been developed in the recent studies by authors with special consideration on the interfacial strength between SMA wires and matrix. Basic characteristics of this actuator is presented in this paper. To drive this moment actuator smoothly, punctual temperature control in real time which includes rapid heating, exact current control and some cooling control is required. Adaptive feedforward control system is, therefore, designed here for this actuator aiming to apply to beam structure. As a result, control effect on beam structure is demonstrated experimentally. Verification of performance of this actuator is also shown.

Inductive transducers with magnetic fluids (MF) for aerodynamic measurements have as essential components one or two pairs of identical electrical coils of circular cross section, uniformly wound. The carcasses of every pair of coils have the role of vertical cylindrical reservoir and communicate at the bottom creating a certical U-shaped tube. At the equilibrium this tuve is half filled with MF. The MF has the role of a magnetic liquid core. This U system measure a pressure difference in gases at the top ends of the carcasses, this one is proportional to the difference between the inductances of the coils. For these transducers the paper presents the mechanical functioning principle the detailed correction solution for inclination and acceleration, a theoretical electronic measuring system having only one element for zero adjustment and also some technical characteristics of these transducers obtained by a numerical simulation method.

Temperature sensing with optical devices is a very promising research field because of many attractive features common to all-optical sensing schemes. Many recent works have presented optical sensors made with fiber optic Bragg gratings where the temperature information is encoded into a wavelength shift of the transmitted or reflected Bragg spectrum. This calls for specialized readout schemes and it cannot be integrated with other electronic circuits needed for calibration and or compensation. On the other hand, all-silicon integrated sensors have many interesting features from their inherent low processing cost to integrability with signal-processing electronics. In this paper we present a novel approach to temperature sensing with optoelectronic devices which relies on the usage of bare silicon as the transducing material. The device is composed by a single mode input waveguide, a MMI region where the higher order modes are allowed to propagate and two output waveguides. The refractive index variation in the MMI section due to temperature shifts induces different phase velocities of the propagating modes. The position of the input and output waveguides together with the length and width of the MMI section are chosen in order to maximize the sensitivity of the device as it will be shown in the full paper. Analytical calculations are presented together with BPM simulations aimed to the maximization of the sensitivity of the sensor. Analytical calculations are presented together with BPM simulations aimed to the maximization of the sensitivity of the sensor.

In this paper a fibre optic evanescent wave absorption sensor for measuring low concentrations of dissolved ammonia in water ranging from 12ppb to 2800ppb is presented. A plastic clad silica core (PCS) fiber with unclad middle region acts as the sensing element. Exposure of this sensing region to water samples containing Nessler’s reagent causes evanescent wave absorption, which increases with increasing concentration of ammonia. The use of a super-bright blue light emitting diode (LED) as light source reduces the size and cost of the system considerably. In order to reduce the effect of power supply fluctuations or ambient variations of the LED, a reference arm and ratio detector are employed. A comparative study between the present sensor and the conventional spectrophotometric method has also been carried out.

When driver and receiver electronics for an ultrasound measurement system are physically implemented, parasitic components are introduced in the system. These may arise from bond wires, circuit board paths or cabling. The parasitic components will influence the excitation pulse behavior as well as amplitude and time of arrival for received pulses. In the system investigated, a coaxial cable is used to connect the transducer with the electronics. The inductance and capacitance of the cable are dominating parasitic components in the system. This paper investigates the effects of these components for varying cable lengths and compares measurements with system simulations using SPICE models. The simulations give highly accurate temporal behavior of the excitation pulse. The peak to peak amplitude and the perceived time of flight of the received echo in a pulse echo system is measured. Amplitude variations of 60% are recorded for cable lengths varied between 0.07 m and 2.3 m., with simulations predicting the same variations. The time of flight is measured using the excitation pulse as time trigger. Variations are up to 40 ns for a total travel time of about 8 μs. The simulations predict this variation within a few ns.

A simple method is proposed for simulating the behavior of shape memory alloys at grain level. Different from many previous models in the literature, this model is applicable for not only proportional load at a constant temperature but also complicate non-proportional load together with temperature variation. The capability of this model is demonstrated by simulating the strain response of a set of combined tensile-shear stress loading.

With the intention of developing devices for optical communications, we have worked upon acousto-optic deflection in the Bragg regime, at 1.55 µm wavelength. Recently, still using the acousto-optic interaction, we have taken an interest in the 2×2 switching function. In this paper, we present an acousto-optic switch architecture based on phased array transducers. This switch is made of a single TeO₂ crystal, in which we superimpose two diffraction gratings created by two RF signals. First, we talk about the acousto-optic interaction, and make a general presentation of the switch's architecture. Then, we present some previous characterisations of the structure, in terms of diffraction efficiency according to the number of piezoelectric transducers electrically supplied and the RF power applied. We also study the diffracted optical beam profiles.

On exposure at different chemical substances several physical quantities of porous silicon, such as reflectivity, photoluminescence, and electrical conductivity, change drastically. In particular, we have used porous silicon microcavities as chemical sensors, measuring resonant peak shifts in the reflectivity spectra due to capillary condensation of the vapor in the silicon pores. Understanding sensor behaviour depends on the dielectric function model and on the interaction mechanism assumed. With proper choices, we can also quantitatively characterize the Porous Silicon Microcavity sensing device features.

In this paper a new method for measuring simultaneously, thickness and refractive index of transparent plates is proposed. The method is based on a very simple lateral variable shear wavelength scanning interferometer. The transparent plate is made to rotate at controlled and constant angular speed. Radiation from a laser diode propagates though the sample and experiences an even number of reflections at the sample-air interfaces. The emerging wave fronts are laterally sheared with a shear depending from the actual angle of incidence. Varying the emission wavelength of the laser source a variation of the phase of interference signal is obtained. In this way, interferometric signals as function of incidence angle for each laser wavelength λ were obtained. Evaluating phase variations in correspondence of normal incidence, by a simple non-linear fit, it is possible to determine the optical thickness n.d. Then, retrieving the phase of the overall interference signal for all available incidence angles and employing the previously evaluated optical thickness, the refractive index value can be determined. Finally, geometrical thickness d was obtained straightforwardly as end result. The effectiveness and straightforwardness of the method has been demonstrated for a silicon sample and also for a z-cut Lithium Niobate sample.

The interactions between viologens and polyaniline of different intrinsic oxidation states in the solid state, under photo-irradiation, were investigated. These interactions were facilitated by depositing a thin coating of polyaniline onto low-density polyethylene films, which have been surface grafted with viologen. The films were characterized by X-ray photoelectron spectroscopy, UV-visible absorption spectroscopy and sheet resistance measurements. The polyaniline coatings were observed to change from the insulating state to the conducting state upon near-UV irradiation. The reaction of the fully reduced form of polyaniline (leucoemeraldine) with viologen is dependent on the presence of oxygen. It is proposed that the conversion of the polyaniline to the conductive state occurs through a protonic acid doping mechanism whereby hydrochloric acid is formed during the ring-opening reaction of viologens with amine nitrogen of the polyaniline upon irradiation of the films. The adhesion of PANI to the viologen-grafted film as assessed by peel tests is good and the stability studies indicated that the conductivity of the photo-irradiated films is stable in air. However, the films undergo rapid dedoping in water, resulting in a loss of conductivity.

Low frequency modes of tower structure generated by a strong wind or by an earthquake occur deterioration or a collapse of structure because stress concentration happens at the root of structure. High frequency modes, on the other hand, are often possible to be disregarded because they can be damped immediately. In general, all vibration modes which are generated in the structure are tried to be suppressed when it is said as 'vibration control'. There remind, however, a lot of problems to realize a stable control in this case. The object of present paper is a pick up and a suppression of specific vibration modes which occur such problems, it means here low frequency modes, among all of generated vibration modes in structure. First of all, a design of modal sensor made of PVDF film is proposed to pick up only low frequency modes separately by using FEM analysis. Then, an applied method of SMA/CFRP hybrid actuator, which can generate great force in a field of low frequency, is explained. By using these PVDF modal sensor and SMA moment actuator, vibration model can be simplified by means of modification to low dimensions. Consequently, modal control system, which suppresses only low frequency vibration modes, is constructed. At the end of the present paper, effect of this control system is demonstrated experimentally.