A new LaSMP smart material exhibits shape memory behaviors and stiffness variation via UV light exposures. This dynamic stiffness provides a new noncontact actuation mechanism for engineering structures. Isogeometric analysis utilizes high order and high continuity NURBS as basis functions which naturally fulfills C 1 -continuity requirement of Euler-Bernoulli beam and Kirchhoff plate theories. The UV light-activated frequency control of LaSMP laminated beam and plate structures based on the isogeometric analysis is presented in this study. The accuracy and efficiency of the proposed isogeometric approach are demonstrated via several numerical examples in frequency control. The results show that, with LaSMPs, broadband frequency control of beam and plate structures can be realized. Furthermore, the length of LaSMP patches on beams is varied, which further broadens its frequency variation ranges. Studies suggest that 1) the newly developed IGA is an effective numerical tool and 2) the maximum frequency change ratio of beam and plate structures respectively reach 24.30% and 6.37%, which demonstrates the feasibility of LaSMPs induced vibration control of structures.

Conductive polymer nanocomposites (CPNCs) have gained a lot of attention by the researchers, in recent times, due to their diverse technological applications in different domains. This paper discusses the additive manufacturing of conductive polymer nanocomposite. Maghemite-Multiwalled carbon nanotubes were synthesized, and later dispersed in an acrylate resin, followed by curing with UV DLP 3D printer, under the presence of external magnetic field. Maghemite-Multiwalled carbon nanotubes showed superior magnetic properties, when compared to Multiwalled carbon nanotubes and lead to improvements in preferential alignment of filler material in the polymer matrix. The initial experimental results show preferential alignment of Maghemite-Multiwalled carbon nanotubes in the polymer matrix under the influence of external uniform magnetic field, at an intensity of 120 Gauss.

Light-activated shape memory polymers (LaSMPs) exhibit stiffness variations when exposed to ultraviolet (UV) lights. Thus, LaSMP could manipulate structural natural frequencies with UV light exposures when laminated on structures. This study aims to experimentally demonstrate the effectiveness of LaSMP frequency control of a flexible beam. The natural frequency of a three-layered Euler-Bernoulli beam composed of LaSMP, adhesive tape and the flexible beam is analyzed and its frequency formulation exhibits the LaSMP stiffness influence. As the LaSMP adopted in this study is a new spiropyran based composition, a generic Young’s modulus model is proposed and then simplified to model the present LaSMP composition. To make sure the experiment is carried out in a homogenous light field, the light intensities of the UV surface light source at different positions are tested. The temperature change of the LaSMP sample under UV exposures is also measured. The time constant of the reverse reaction and the threshold intensity of the reverse reaction are measured. LaSMP Young’s modulus variation is tested with a uniaxial tension experiment. The constitutive model of LaSMP’s Young’s modulus is validated by experimental data. With these preparations, the LaSMP laminated flexible beam model is exposed to the UV lights and its natural frequencies are identified with a data acquisition and analysis system. The maximum natural frequency variation ratio achieves 5.67%. Comparing both theoretical and experimental data of natural frequency control, this study also validates the LaSMP Young’s modulus constitutive model.

The light-activated shape memory polymer (LaSMP) is sensitive to ultraviolet light with specific wavelength. It is featured with dynamic stiffness. In this study, LaSMP is used to control the vibration of thin ring shells induced by external loading. Firstly the variation of LaSMP’s Young’s modulus is modeled. The mathematical model reflects the influence of light intensity, the decay coefficient and thickness of LaSMP. Besides, the model is suitable for LaSMPs with different reaction orders. Then, with Lamé parameters and the radii of rings the governing equations of the flexible ring laminated with LaSMP actuators are established. Love operators of LaSMP actuators are derived. Based on the mode expansion method, the modal forces of external loading and LaSMP actuators are given. The modal participation factors are analyzed with the modal forces. As the variation of Young’s modulus to the light intensity is nonlinear, the control effect of LaSMP actuators to common harmonic excitation is not perfect. Because the neural network control is effective to identify complex models, it is introduced to adjust the profile of light intensity. In the case study, the model of LaSMP’s Young’s modulus is validated with the experimental data. Then the forced harmonic responses of the ring are studied. For the mode n =2, the modal participation factor is reduced by 47.7% with the control of LaSMP actuator. To further enhance the control effect, the phase shift method is applied. With π/6 phase shift, the modal participation factor is reduced by 80.8%. With the neural network control method, the modal participation factor is cut down by 98.1%. The study shows that LaSMP actuator provides a new choice to control the forced vibration of flexible rings. It is also possible to apply LaSMP actuator to vibration control of other thin shell structures.

A sensor is unobtrusive if it doesn’t interfere with the design, mechanical properties, and the functionality of the structure it is integrated with. This paper discusses the development of unobtrusive piezo-resistive sensors and their production using additive manufacturing. Short carbon fibers were dispersed in an acrylate resin and subsequently cured with UV DLP 3D printer to be used as a strain-sensing device. Varying the amount of carbon fiber resulted in resistivity variation of the composite. The composite was found to be piezo-resistive, and gauze factor at a concentration of 12% carbon fiber by volume was obtained through mechanical load testing.

To design and optimize for capabilities of additive manufacturing processes it is also necessary to understand and model their variations in geometric and mechanical properties. In this paper, such variations of inkjet 3D printed parts are systematically investigated by analyzing parameters of the whole process, i.e. storage of the material, printing, testing, and storage of finished parts. The goal is to both understand the process and determine the parameters that lead to the best mechanical properties and the most accurate geometric properties. Using models based on this understanding, we can design and optimize parts, and fabricate and test them successfully, thus closing the loop. Since AM materials change rapidly and this process will have to be repeated, it is shown how to create a cost and time efficient experimental design with the one-factor-at-a-time and design of experiments methods, yielding high statistical accuracies for both main and interaction effects. The results show that the number of intersections between layers and nozzles along the load-direction has the strongest impact on the mechanical properties followed by the UV exposure time, which is investigated by part spacing, the position on the printing table and the expiry date of the material. Minor effects are found for the storage time and the surface roughness is not affected by any factor. Nozzle blockage, which leads to a smaller flow-rate of printing material, significantly affected the width and waviness of the printed product. Furthermore, the machine’s warm-up time is found to be an important factor.

While thin beams are widely used structural elements in Micro-Electro-Mechanical-Systems (MEMS) there are very few studies investigating the laser machining of clean high aspect ratio silicon beams. This work presents a systematic study of selected influencing cutting parameters with the goal of machining high aspect ratio beams with low side wall surface roughness (R a ) and high cross section verticality, i.e. low taper angle. The Taguchi method was used to find the optimal setting for each of the selected parameters (pulse frequency, laser diode current, pulse overlap, number of patterns to be marked, gap size between patterns) utilizing orthogonal arrays and signal-to-noise (S/N) ratio analysis. Double-sided clamped beams of 100μm width and 10mm length were machined in silicon wafers of 525μm thickness using a nanosecond solid-state UV laser system (355nm wavelength). Our experimental results show that beams with an aspect ratio as high as 17.5 can be manufactured. Furthermore, a surface roughness of R a = 0.37μm and taper angle of α = 2.52 degrees can be achieved. This will make the fast fabrication of MEMS devices with aspect ratios as high as those from deep reactive ion etching possible.

The power spectrum of human heart rate measured over 24 h exhibits “power-law” 1/f alpha-type spectral behavior with alpha approximately 1. This may be one of the reasons why 1/f noise help people make relaxed, or feel comfortable. As a result, people feel relaxed by looking at a candle light, listening to the sound of ocean wave, or feeling the breezing wind because all of these natural phenomenon is based on the 1/f noise fluctuation. Considering this feature, a technical approach of 1/f noise fluctuation has been applied to various industry products, ranging from light illumination, fan control, temperature control, etc. to implement cozy products. For example, one typical example would be a lighting product mimicking a candle light, which illuminate just like a true candle. A candle light provides a cozy atmosphere to relax our mind by forgetting severe business issues, which is because of the nature of 1/f noise fluctuation as mentioned above. However, it is not suitable to do something important by concentration under a candle light because of the changes of brightness and the blinking nature of candles. This study designs and develops 1/f noise-fluctuated cozy lighting system with stable brightness and chromaticity without blinking so that people unconsciously feel relaxed under this lighting system without noticing the 1/f noise fluctuation and concentrate on work or operation. In order to implement this lighting system, combination of two types of white LED lights were used. White LED lights are manufactured by the combination of different colors having different spectrum. For example, Blue with YAG fluorophore, Blue with RG fluorophore, UV with RGB fluorophore, etc. provide all white LED lights. This means that it is possible to make two different types of LED lights which have the same white color with different combination of spectrums. If the two white colors of the two LED are the same, nobody cannot notice when the two LEDs are switching over each other, periodically or randomly. People only think that the white color is constantly provided by the white LED light. However, if the switching is based on 1/f noise fluctuation, some positive effect can be expected under this lighting system. This paper shows the overview of the idea of 1/f noise-fluctuated cozy lighting system, and then presents the two basic challenges of the idea towards concentration improvement; Combination of two types of white LED and 1/f noise-fluctuated switching system. These two challenges are presented using a prototype lighting systems developed in this study.

At the microscale, the ability to precisely move objects on the scale of microns is a challenge. One method is to use microbiorobots (MBRs), constructed of a neutrally-buoyant microstructure powered by a monolayer of swarmer flagellated bacteria adhered to the surface. The bacteria swim to propel the microstructure in a fluidic environment in the absence of external forces. The trajectory is a combination of translation and rotation, with the rotation generally observed to be clockwise when viewed from above. In order to create a dynamic model of the inherent motion of MBRs, we use UV light to immobilize the bacteria on different regions of an MBR and characterize the resultant motion. We show that the bacteria on the edge of the structure have different force contributions than those in the center of the microstructure where the flagella cannot interact with the surface under that MBR. This is a step towards improved accuracy in the control of MBRs when external forces are applied for manipulation.

The monitoring and control of combustion systems co-firing coal and biomass is a critical consideration when aiming to increase the proportion of biomass being combusted. This is because it is likely that the combustion will become increasingly unstable as the biomass proportion increases. In order to develop a flame monitoring and control system, flame signal data sets were collected from combustion measurements taken on a 500kW pilot scale combustion test facility. The sensors used were photodiodes with sensitivities in the UV, visible and IR wavelengths. The analysis of these data, identified flame features that can be related to operational parameters such as flame stability, excess air level, NOx and CO emissions. These features were then applied in the development of an intelligent flame monitoring and optimisation system for individual burners based on these low cost sensors. The testing of the monitoring and control system on a pilot scale burner and at full scale are described in this paper.

We present a method to detect the non-uniform elastic property changes of sensor coatings on microcantilever arrays due to radiation, analyte binding or adsorption. The method uses measurements of the resonance frequencies of higher order flexural modes to identify with high sensitivity the location and magnitude of non-uniform elasticity changes in a microcantilever coating. We validate theoretical predictions and demonstrate the method by monitoring the time evolution of resonance frequencies of different flexural modes of microcantilevers functionalized with a small drop of a photosensitive polymer as it is exposed to ultraviolet (UV) radiation. The method is particularly well-suited for measuring quantitatively the time varying elastic properties of thin films or biological materials attached to microcantilevers.

Nano-imprinting lithography (NIL) has been developed over 15 years and has shown its great potentials for nanopatterning and nano-fabrication. In this paper, new ideas on improving current nano-imprinting methods have been proposed and preliminary experimental tests are carried out. These proposed nano-imprinting methods are all based on the utilization of pulsed laser sources, either in UV or IR region, and can be easily implemented into a roller-based configuration, which is more effective and much faster than conventional planar type nano-imprinting methods. First of all, based on the Laser Assisted Direct Imprinting (LADI) method proposed in 2002, a modified roller-based LADI method is developed by applying a cylindrical quartz roller for mechanically loading as well as for optically focusing of a deep UV laser beam into a line. This modification not only fulfills a continuous type of LADI process but also more efficiently utilizes the laser energy so that large-area LADI is possible. Experimental testing demonstrates an imprinting rate of 3∼10 cm 2 /min. Secondly, a new nano-imprinting lithography based on pulsed infrared laser heating is proposed and demonstrated. It utilizes the partial transparency of silicon crystals at IR spectrum to heat up the photo-resist layer. Possible improvements and applications on this IR-NIL will be addressed. Finally, a new method of direct contact printing and patterning of a thin metal film on silicon substrate based on the idea of nano-imprinting is presented. This method combines the effects of loaded contact pressure and IR pulsed laser heating at the metal-film/substrate interface to form a stronger bonding between them, and therefore complete the direct pattern transferring of metal film on substrate. Good experimental results are observed and possible applications will be discussed.

This article discusses the current status and achievements of R2R technology for large area nano-scaled optical devices developed at MSL/ITRI. Firstly, a single layer of nanostructure on polymer film is designed for anti-reflection purpose by finite difference time domain (FDTD) method in the visible light spectrum. The conical array with around 1 aspect ratio, like moth-eye shape and showing superior performance in the optical simulation, has been adapted for the R2R experiments. The development of R2R process includes roller machine design and fabrication, roller mold design and making, development of rolling imprint process, characterization of rolled devices. In this study, large area (200mm *200mm) Ni template was fabricated with DUV exposure, followed by dry etching and electroforming process, respectively. Then, the template was bonded on the roller mold with magnetic film to make nanostructure roller mold. With the delicate nanostructure roller mold, systematic experiments have been conducted on the home-made roller machine with various parameters, such as linear speed, dose rate, and material modifications. The duplicated nanostructure films show very good optical quality of anti-reflection (AR < 1%) and are in good agreement with the theoretical predictions. Besides, the duration of the roller mold has been highly promoted to hundreds of imprint in the UV embossing process.

Researchers have demonstrated that imprint lithography techniques have remarkable replication resolution and can pattern sub-5nm structures. However, a fully capable lithography approach needs to address several challenges in order to be useful in nano-manufacturing applications. This paper presents the key technical challenges as well as the progress achieved to-date in these areas. A promising nanoimprint technique that has been previously discussed in the literature is a UV curing technique known as Step and Flash Imprint Lithography (S-FIL). In this article, a variant of the S-FIL process — known as drop-on-demand UV nano-imprint process — that addresses many of the key manufacturing challenges is discussed. This process has the ability to address challenges such as process repeatability in residual layer control, low defectivity, ability to fully automate the lithography process, nano-resolution alignment, and the ability to handle pattern density variations. All nano-imprint lithography techniques essentially replicate the patterns present in a master mold (or template). One of the demanding challenges is the creation of this template. Patterning, metrology, inspection, and defect repair issues relevant to template fabrication are discussed. Finally, with a brief discussion of near-term practical applications in the areas of photonics, magnetic storage, and CMOS devices is presented.

We report easy and fast fabrication methods to prepare densely packed polystyrene (PS) and silicon nano-dots using one-step excimer laser irradiation on cylindrically nanopatterned block copolymer materials, without any additional selective etching steps before a non-selective etching. Preferential etching in more ultraviolet (UV)-sensitive block component, and non-selective removal of all block components allowed transferring nanopatterns in block copolymer masks to inorganic silicon substrates, when an appropriate laser intensity was used. Surface melt flows of block components, which severely undermine the initial orders of nanopatterns in a block copolymer mask, were observed at the laser intensity near the ablation threshold of the less UV-sensitive component. Thus, in order to obtain mask-image-like topographic nanopatterns on the target material surfaces, the intensity of excimer laser radiation should be sufficiently lower than the ablation threshold of the less UV-sensitive component as long as the intensity is higher than that of the more UV-sensitive component. Numerical analyses on the photothermal excimer laser ablation in binary mixture systems predicted the presence of a matrix-assisted excimer laser ablation in the less UV-sensitive component at the laser intensity lower than its ablation threshold, owing to the heat conduction from the more UV-sensitive component during the nanoscopic level of time duration.

Temperature profiles in PET (Polyethylene Terephtalate), PBT (Polybutylene Terephtalate), and PS (Polystyrene) films created due to excimer laser irradiation were estimated analytically from the model of semi-infinite heat flux and numerically from the model based on 1-D heat equation. For the analytical estimation of temperature profile, we initially assumed that all of the irradiated excimer laser energy was confined in surface, and the energy was considered as a constant heat flux during the laser irradiation period. Calculation results showed that this assumption is somewhat inadequate for polymer materials especially for the polymers with low UV absorption coefficients, because we could not exclude the absorption of excimer laser energy in bulk. In order to reduce the error from this assumption, temperature profiles were estimated from numerical solution, which included a heat generating function representing absorption of excimer laser beam in polymer. Temperature measurement results showed a good agreement with this calculation, but only when ablation was not significant (i.e., for PS).