Flexible Panel Research Articles

Optimization of multi-layer graphene/PMMA synthesized by low-pressure chemical vapor deposition from acetylene precursor

High quality and large-scale graphene are required for large-scale applications, especially flexible transparent conductive touch-screen panels. Chemical vapor deposition is so far the best method for the synthesis of high-quality graphene on the large scale. In this work, we synthesized multi-layer graphene on copper foils by low-pressure chemical vapor deposition from acetylene precursor at the flow rate of 20-40 mL/min and with reaction times from 10-30 minutes. Graphene on copper foils was then coated with PMMA and transferred by a wet chemical etching method. The transmittance and electrical properties of graphene on polymer were investigated. The Raman spectra of graphene synthesized with the acetylene flow rate of 30 mL/min for 10 minutes showed the characteristics of bi-layer graphene (I2D/IG = 1.6) with the lowest sheet resistance values (2.05 kΩ/sq) and the best transmittance (73 %).

The identification of minimum-weight sound packages

Generally, heavier noise control treatments are favored over lighter treatments since heavier acoustical materials generally insulate (block) noise sources more effectively than do lighter materials. In automotive applications, however, heavier materials cannot always be adopted because of concerns about the total weight of the vehicle. Thus, it would be useful to identify lightweight acoustical treatments that can mitigate vehicle interior noise. Automotive sound packages have both absorption and transmission characteristics, and there is inevitably a trade-off between these two. Therefore, it is important to study the exchange between the absorption and transmission of acoustical materials particularly as it pertains to weight. Here, we describe a procedure, based on plane wave analysis, that can be used to identify weight reduction opportunities by adjusting the acoustical properties of a generic sound package, consisting of a fibrous layer and a flexible microperforated panel surface treatment, so that it meets a target sound pressure level in a downstream interior space. It has been found for the configuration studied here that there are lightweight sound package configurations that can maintain acoustical performance equivalent to that of heavier noise treatments, and further, it has been found that the lightest treatments tend to favor barrier performance rather than absorption. Further, the impact of acoustical leaks is considered, and it has been found that even very small leaks can result in a very substantial weight penalty if a specified level of acoustical performance is to be ensured.

Multi-Scenarios Attitude Control of a Satellite with Flexible Solar Panels

The development of space mission design requires mathematical modelling and related numerical simulations. These latter are very important to select the Attitude Determination and Control Subsystem hardware against the mission requirements for attitude and orbit specifications. In this paper, a nonlinear dynamic modelling framework is presented for one degree of freedom of a flexible spacecraft. The dynamics of the structure are derived in the nonlinear Euler equations form for a circular orbit; the gravity-gradient torque is introduced as an external perturbation. The resulting model is used to perform attitude control precision of the pitch axis rotational manoeuvre, via several simulations for various in-orbit operating scenarios, to highlight the coupling effect between the main body and the flexible panels. For this purpose, the spacecraft is considered as a rigid cubic-body with two flexible solar panels deployed on each side of its roll axis. The simulation results show that the flexible motion of the panels has a substantial impact on the spacecraft dynamical responses, especially when considering the external perturbation effects. A classical controller is implemented to control the system three axes manoeuvres and to suppress the flexible panels’ distortions. Numerical results confirm the effectiveness of the proposed model to demonstrate the coupling effects and the control strategy.

Relative Attitude Dynamics and Control of Spacecraft Formation Flying Considering Flexible Panels

As a key technology for orbital applications, researches on spacecraft formation flying (SFF) attract more attention. However, most of existing researches about dynamics and control of SFF focus on rigid spacecrafts without considering the effect of flexible attachments (such as flexible panels). In this paper, relative attitude dynamics and active control of SFF for a flexible spacecraft (follower spacecraft) and a rigid spacecraft (target spacecraft) are investigated. Firstly, a dynamic model of the flexible spacecraft is established by the principle of angular momentum. Then, the equation of relative attitude dynamics between the flexible spacecraft and the rigid spacecraft is derived by the quaternion to represent the attitude relation of the two spacecrafts. Finally, an attitude feedback controller is designed for the SFF system, and its stability is proved by the Lyapunov stability theory. Simulation results indicate that the panel flexibility has an obvious influence on the dynamic behaviour of the system, the designed controller can effectively control the attitude of the two spacecrafts to achieve synchronization, and the elastic vibration of the panels may be suppressed simultaneously.

Exploring the response of a thin, flexible panel to shock-turbulent boundary-layer interactions

The use of nonlinear, dynamic methods for the simulation of aerospace structures has increased dramatically in recent years [1]; however, very little relevant experimental data exists to properly guide these developments. An experimental campaign was initiated by the AFRL Structural Sciences Center (SSC) for three reasons: (1) to observe and measure the effect of turbulence, shock boundary-layer interactions (SBLI) and heated flow on an aircraft-like panel; (2) to explore severe structural events (dynamic instabilities and material failure); and (3) to refine full-field and non-contacting experimental measurement techniques necessary to characterize the flow environment and structural response. All of the objectives were achieved. The panel response to turbulent, heated flow and sensitivity to panel back-pressure modulation was studied, with large-deformation limit cycle behavior leading to panel failure, observed and measured. For the first time, the 3D Digital Image Correlation (DIC) technique was also used to record the panel behavior while filming through the flow and SBLI environment. Finally, fast reacting pressure sensitive paint (PSP) was used, concurrently with 3D DIC, to record the dynamic pressure across the panel surface.

Sound radiation from a finite perforated panel set in a rigid baffle: A fully coupled analysis

A fully coupled formulation is presented for sound radiation from a finite flexible perforated panel set in an infinite rigid unperforated baffle. The panel is excited by a point harmonic force and radiates sound into the acoustic medium on both sides of the baffle. Prior to coupling with the fluid, the change in the inertial and stiffness properties of the panel due to perforations and their effect on the in vacuo natural frequencies and mode shapes are accounted for using the receptance method. The coupled acoustic and structural equations are formulated using the 2-D wavenumber transforms. Since the formulation is in terms of the panel velocity, a certain square root singularity that typically appears in the denominator is avoided. The self- and inter-modal coupling coefficients are evaluated either analytically or numerically. The radiated power, panel mean quadratic velocity and radiation efficiency plots are obtained for different perforation ratios for both center and off-center excitations. At first, our formulation is validated against an unperforated case using a study available in the literature. Next, for our perforated panel case, we assume that both the half-spaces are filled with the acoustic fluid. It is observed that the radiation efficiency decreases with the increase in the perforation ratio, irrespective of the surrounding acoustic medium. However, for the water-loaded panel, the radiation efficiency is found to be lower than when the panel is immersed in air. It is found that for a light fluid like air, a one-way coupled formulation is adequate. The natural frequencies of a water-loaded perforated panel are also presented. It is found that for a given mode, the natural frequency increases with increase in the perforation ratio.

Mechanical simulation of foldable AMOLED panel with a module structure

Abstract The stress analysis of the flexible AMOLED panel is a fundamental study for designing optimal structures with good foldability. Current research assumes linear elastic models. In the present work, A visco-hyperelastic constitutive model was employed to describe the nonlinear behavior of the optically clear adhesive (OCA). The finite element method for simulating the folded panel was constructed to analyze the effect of panel structure on the stress and strain distributions. Compared with the bending state of the single device, the flexible panel module is shown to have multiple neutral planes. The maximum longitudinal stress of the AMOLED device is located at the folding symmetry, while the maximum strain in the OCA layer is located at the transition area between the bending and unbending areas. Finally, the simulated results show that increasing the thickness of the first OCA layer which located between the cover window and the polarizer is more efficient for preventing peeling effect or delamination occurred to the panel.

Cu(In,Ga)Se2 monograin powders with different Ga content for solar cells

Monograin layer (MGL) solar cell technology based on CuIn1-xGaxSe2 (CIGSe) monograin powder crystals is a promising approach for the future low-cost production of flexible solar panels. In this study, CuIn1-xGaxSe2 monograin powders (0 ≤ x ≤ 1) were prepared from binary compounds in the liquid phase of potassium iodide as flux material in evacuated quartz ampoules at 720 °C. The crystal structure and the lattice parameters of the CIGSe monograin powder crystals were determined by using X-ray diffraction analysis. A linear decrease of the lattice parameters with increasing Ga concentration was detected. The photoluminescence (PL) spectra of the CIGSe crystals were dominated by the edge emission band that shifted towards higher energies with increasing Ga content. Moreover, additional deep PL band (below 1.0 eV) appeared for Ga contents above x = 0.21 showing higher relative intensity with increasing Ga content. The effective bandgap energy of the CIGSe monograin powder materials ranged from 1.0 eV to 1.68 eV as the [Ga]/([In] + [Ga]) ratio increased from 0 to 1.0. An efficiency of 12.8% (active area) was obtained with the MGL solar cell based on CuIn1-xGaxSe2 monograin powder with Ga content of x = 0.21.

High-Resolution Flexible AMOLED Display Integrating Gate Driver by Metal–Oxide TFTs

This letter proposes a high-resolution [200 (RGB) * 600, 282 PPI) flexible active matrix organic light emitting display (AMOLED) integrating a new gate driver, of which the substrate is a polyimide material. Flexible In–Zn–O thin-film transistors (TFTs) with back channel etched structure reveal a good stability at different curvature radii. The integrated gate driver employing bi-side driving method consists of seven TFTs and two capacitors with the advantages of simple topology, low power, full-swing output, and small area. The conventional 2T1C pixel circuit with top emission structure is applied to the proposed flexible AMOLED panel. And the flexible panel has a good full-color display quality without obvious defects at the bending condition. It is shown that the output signals of the proposed gate driver have no distortion and good noise suppressed characteristics even up to 600 stages and maintain stable under a long-time continuous operation up to 15 days.

Aerothermoelastic experimental design for the AEDC/VKF Tunnel C: Challenges associated with measuring the response of flexible panels in high-temperature, high-speed wind tunnels

There is a lack of carefully-crafted aerothermoelastic experimental data that can be used for validation purposes. To address this need, the Air Force Research Laboratory Structural Sciences Center is currently planning an experiment in the Arnold Engineering Development Center von Kármán Facility Tunnel C to examine the aerothermoelastic response of flexible models that are representative of high-speed aircraft outer mold line panels. The test will utilize an infrared camera and the stereo digital image correlation technique to provide simultaneous, full-field measurements of the surface temperature and panel motion. This paper provides an overview of the proposed experiment and addresses challenges relevant to aerothermoelastic testing in high-temperature, high-speed wind tunnels.

Robust adaptive vibration control of an underactuated flexible spacecraft

Designing a controller for multi-body systems including flexible and rigid bodies has always been one of the major engineering challenges. Equations of motion of these systems comprise extremely nonlinear and coupled terms. Vibrations of flexible bodies affect sensors of rigid bodies and might make the system unstable. Introducing a new control strategy for designing control systems which do not require the rigid–flexible coupling model and can dwindle vibrations without sensors or actuators on flexible bodies is the purpose of this paper. In this study, a spacecraft comprising a rigid body and a flexible panel is used as the case study, and its equations of motion are extracted using Lagrange equations in terms of quasi-coordinates. For oscillations on a rigid body to be eliminated, a frequency estimation algorithm and an adaptive filtering are used. A controller is designed based on the rigid model of the system, and then robust stability conditions for the rigid–flexible system are obtained. The conditions are also developed for the spacecraft with more than one active frequency. Finally, the robust adaptive vibration control system is simulated in the presence of resonance. Simulations’ results indicate the advantage of the control method even when several active frequencies simultaneously resonate the dynamics system.

DCT/IDCT Constant Geometry Array Processor for Codec on Display Panel

Algorithms, architectures and 8 X 8 processing element chip design are discussed based on constant geometry 2-Dim. DCT and IDCT. Both DCT and IDCT can be computed with the same hardware for image codec applications. An array of identical PEs is used for butterfly as well as recursive addition stages only with programming of regular interconnections between stages for fault tolerance of system on panel or flexible display panel. Also methodologies to optimize computation speed and amount of required hardware are discussed. An efficient distributed arithmetic ROM for coefficient multiplication is proposed to minimize chip area and to facilitate the PE programming. Chip area, computation time, with image qualities are evaluated with advantages.

The effect of photovoltaic panels on the microclimate and on the tomato production under photovoltaic canarian greenhouses

Photovoltaic greenhouses are mixed systems, combining electricity and agricultural production in the same area. Moreover, this type of greenhouse conserves all the properties of a conventional greenhouse, as well as offering the possibility of producing and selling electricity.The aim of the present study is to assess both the impact of the shade caused by the photovoltaic panels on the microclimate and the quality of fruits in the greenhouse. Measurements were carried out in an experimental Canary type greenhouse covered with flexible photovoltaic panels on 10% of its total roof area.Results illustrate that this occupancy rate of the photovoltaic panels arranged in checkerboard pattern does not have a significant effect on the agronomic parameters e.g. height, stem diameter and tomato yield, and climatic parameters under the greenhouse cover. Additionally, the presence of photovoltaic panels has a negative effect on the development of the population of Tuta absoluta.

Low-temperature poly Si TFTs via BLDA for a Ne-sputtered Si film using sputtered gate SiO2

ABSTRACTAmorphous SiO2 and amorphous Si films were deposited on glass using radio frequency (RF) sputtering, and were subsequently poly-crystallized using blue-laser diode annealing (BLDA) scanned by a CW beam. Ne, which has a smaller atomic radius than Ar, was used for the sputtering of the Si film. For the gate insulator, a small amount of O2 gas diluted with Ar was flown during the sputtering to optimize the SiO2 film with a low leakage current. A simple TFT structure with a metal source and drain (S/D) was adopted to realize a low-temperature process with a low fabrication cost. Furthermore, to confirm the effectiveness of the sputtered gate oxide, a poly-Si TFT adopting a Si film deposited using plasma-enhanced chemical vapor deposition (PE CVD) for the channel was fabricated and was compared with the TFT with a sputtered Si film for the channel. Reasonable Vg-Id characteristics were obtained for both poly-Si TFTs. The TFT structure with a metal S/D formed through a low-temperature sputtering-based process is expected to be applied to Si TFTs on an arbitrary flexible panel.

A uW Backscatter-Morse-Leaf Sensor for Low-Power Agricultural Wireless Sensor Networks

Nowadays, the monitoring of plant water stress is of high importance in smart agriculture. Instead of the traditional ground soil-moisture measurement, the leaf sensing is a new technology, which is used for the detection of plants needing water. In this paper, a novel, low-cost, and low-power system for leaf sensing using a new plant backscatter sensor node/tag is presented. The latter, can result in the prevention of water waste (water-use efficiency), when is connected to an irrigation system. Specifically, the sensor measures the temperature differential between the leaf and the air, which is directly related to the plant water stress. Next, the tag collects the information from the leaf sensor through an analog-to-digital converter, and then, communicates remotely with a low-cost software-defined radio reader using monostatic backscatter architecture. The tag consists of the sensor board, a microcontroller, an external timer, and an RF front-end for communication. The timer produces a subcarrier frequency for simultaneous access of multiple tags. The proposed work could be scaled and be a part of a large backscatter wireless sensor network. The communication protocol exploits the low-complexity Morse code modulation on a 868 MHz carrier signal. The presented novel proof-of-consent prototype is batteryless and was powered by a flexible solar panel consuming power around $20~\mu \text{W}$ . The performance was validated in an indoors environment where wireless communication was successfully achieved up to 2 m distance.

Dynamics analysis of planar rigid-flexible coupling deployable solar array system with multiple revolute clearance joints

Abstract This paper numerically analyzes action of journal at clearance joint and interaction of journal between multiple clearance joints to reveal the dynamic behavior of planar rigid-flexible coupling solar array system considering joint clearance in depth. A typical solar array model used is composed of a rigid main-body described by Nodal Coordinate Formulation (NCF) and two flexible panels described by Absolute Nodal Coordinate Formulation (ANCF). The system consists of two torque springs, one closed cable loop (CCL) configuration, two latch mechanisms and two clearance joints. The normal contact force effect and tangential friction effect at clearance joint are considered by using nonlinear contact force model and amendatory Coulomb friction model, respectively. Action and interaction of clearance joints are studied to indicate motion property of journal in initial phase, deployment phase and post-lock phase, which provide foundations for effect analysis of overall dynamic behavior. Then comparison results reveal the effects of joint clearance, panel flexibility and their coupling on dynamics of solar array system at these three phases. Coupled with clearance at collision phase, elastic vibration property of flexible panels dominates to cause system shock; while coupled with clearance at contact phase, suspension damping property of flexible panels dominates to steady the system. Finally, rational distribution of clearance size may provide a way to balance wear degree between joints. Decrease joint clearance with more intense collision could reduce the wear depth and balances wear degree between clearance joints.

Improvement of the sound absorption of flexible micro-perforated panels by local resonances

Abstract To further improve the sound absorption enhancement of flexible micro-perforated panels (FMPPs), a new sort of perforated sound absorbers – metamaterial-based micro-perforated panels (MMPPs) – is proposed by combining a micro-perforated host panel and local resonators (LRs) attached on a sub-wavelength scale, targeting the flexural waves. Theoretical and numerical models show that MMPPs are able to further enhance sound absorption in a wide frequency range. The theoretical model is developed based on the effective medium method as the structural wavelength in the host panel is much larger than the distance between the LRs, and the full simulation model, including visco-thermal effects, is conducted by utilizing multi-physical coupling integrated in COMSOL. Besides, a structural finite element unit cell method is used to evaluate the stop band behavior of the MMPP. Good agreement is achieved between the theoretically predicted acoustical properties and the simulation results for both conventional FMPPs and the proposed MMPPs, validating the numerical and theoretical models. Both models reveal that the sound absorption enhancement of the MMPP stems from the resulting acoustic surface impedance improvement, caused by the sub-wavelength attached local resonances. The effect of key properties of the LRs (i.e. mass, damping and multiple resonances) on the sound absorption performance of MMPPs is then analyzed by applying the theoretical model and effective frequency-adjustability of the absorption enhancement performance is found. The proposed MMPP shows great potential for the noise reduction industry.

(Invited) Advanced Crystallization Using Blue Laser-Diode Annealing for Low Temperature Poly Si TFTs

Laser Crystallizations using Blue Laser-Diodes Annealing (BLDA) as well as conventional Excimer Laser Annealing (ELA) are discussed for mounting the TFTs on flexible panels. On glass, high crystallinity of Si films can be obtained by using multi-shots ELA as well as CW laser scanning [1, 2]. There are some issues for Si film after ELA, such as rough Si surface or shots MURA including the fabrication cost. As a result of scanning BLDA for thin Si films, remarkable crystallization occurs with keeping the surface smooth not only for CVD film but also for sputtered Si film [3]. By changing the laser power of 445 nm beam, the grain size can be controlled from micro-grains to large grains as well as to anisotropic long crystal grains [4]. For the Si films of heavily phosphorus doped condition, the resistivity decreased drastically due to the increase in the carrier mobility with high carrier concentration after BLDA of single beam scanning as well as after multi-shots ELA [5]. To realize high performance poly Si films directly not only on flexible glass [6] but also on flexible plastic sheet, effective laser annealing for high quality Si film by low temperature deposition is expected and a design for the thermal buffer layers on flexible sheet is effective [7]. To perform ultra-low temperature TFT process, metal source/drain structure without using ion implantation is also proposed. High performance poly Si TFTs with low fabrication cost on flexible panel should be possible not only for n-channel but also for p-channel [8, 9]. References M. Tai, M. Hatano, S. Yamaguchi, S. K. Park, T. Noda, M. Hongo, T. Shiba and M. Ohkura, Proc. of AM-LCD, TFT3-3, p.231 (2002)T. Noguchi, Mat. Res. Soc. Symp. Proc., 557, p.213 (1993),T. Okada, K, Sugihara, S. Chinen and T. Noguchi, J. Korean Phys. Soc., 66, No.8, pp.1266-1269 (2015). .T. Noguchi, J. Inf. Display, 11, No.1, p.12 (2010).T. Noguchi and T. Okada, J. of Inf. Display, 15, No.1, p.47 (2014).T. Harada, F. Gakiya, Y. Ishiki, T. Okada, T. Noguchi, K. Noda, A. Suwa and H. Ikenoue, Proc. of IDW, AMDp2-11L, p.444 (2016).T. Okada, J.D. Mugiraneza, K. Shirai, T. Suzuki, T. Noguchi, H. Matsushima, T. Hashimoto, Y. Ogino and E. Sahota, Jap. J. Appl. Phys. 51, 03CA02 (2012).K. Sugihara, K. Shimoda, T. Okada and T. Noguchi, J. Inf. Display, 18, No.4, 173-176 (2017).T. Ashitomi, T. Harada, T. Okada, T. Noguchi, O. Nishikata and A. Ota, J. Inf. Display, 18, No.4, 185-189 (2017).

Robust adaptive control of a 6-DOF space robot with flexible panels

Robust adaptive control of a 6-DOF space robot with flexible panels are investigated in this paper. Dynamic model of the robot system is present firstly. Based on computed torque control method, a robust adaptive controller considering the uncertainties of the robot system is proposed to achieve the trajectory tracking and to suppress the elastic vibrations of the panels, and the stability of the controller is guaranteed by the Lyapunov stability theory. The trajectory tracking is performed by using the designed controller. Simulation results indicate that the designed controller can effectively make the robot system with uncertain parameters reach a desired target and the elastic vibration of the panels may be suppressed simultaneously.

Effects of Shock Location on Aeroelastic Stability of Flexible Panel

Focusing on the aeroelastic stability of heated flexible panel in shock-dominated flows with arbitrary shock impingement location condition, a systematic theoretical analysis model is established. The von-Karman large deflection theory is used to account for the geometrical nonlinearity. Local first-order piston theory is employed in the region before and after shock to estimate the aerodynamic pressure. The results show that the shock impingement location has a significant effect on the stability of the flexible panel. The change of the critical dynamic pressure (for which flutter onset occurs) is not a monotonic function of the shock impingement point from one endpoint to the other. Specifically, the nondimensional critical flutter dynamic pressure increases as the shock impingement points move from the left to the right in the middle region, and the value of the critical flutter dynamic pressure varies substantially as the shock is located near the boundary of the panel. The variation is larger for higher shock strength. For a large shock strength, panel can buckle (or diverge) rather than only flutter even without thermal stresses. The sensitivity of the panel dynamics to the shock impingement location may have interesting implications for the case of a moving incident shock.