Dielectric Membrane Research Articles

Realization of a highly sensitive mass sensor in a quadratically coupled optomechanical system

We propose and analyze an efficient scheme for realizing high-sensitive mass sensor in a quadratically coupled optomechanical system via nonlinear second-order sideband process. This is achieved by exploiting a well-established optomechanical circumstance, where a degenerate parametric amplifier (DPA) is embedded into a membrane-in-the-middle cavity driven by a strong control field and a weak probe pulse. Beyond the conventional linearized approximation, we derive analytical expressions for the efficiency of a second-order sideband and the sensitivity of a mass sensor by using a perturbation method. In this scheme, an added mass deposited on the dielectric membrane can be measured by monitoring the efficiency variation of second-order sideband generation. Using experimentally achievable parameters, we identify the conditions under which nonlinear gain of DPA allows us to enhance the efficiency of a second-order sideband and improve the sensitivity of a mass sensor beyond what is achievable in the linearly coupled optomechanical system based on the detection of mechanical frequency shift. More importantly, we also find that the maximum efficiency of a second-order sideband and the optimum sensitivity of a mass sensor simultaneously serve as an efficient detection for the added mass of a membrane when a control field and nonlinear gain of DPA become strong. The present proposal offers a practical opportunity to design an all-optical nonlinear mass sensor at the picogram level.

Temperature distribution on dielectric membrane structures for sensitive elements of semiconductor gas sensors

The aim of this article is to show a simulation of temperature distribution on dielectric membrane structures with membranes of different dielectric materials in the measuring mode of a semiconductor gas sensor. The simulation results were obtained using the software package Synopsys TCAD. In various moments of the measuring cycle were obtained two-dimensional temperature distributions on membrane structures. Dependencies of temperature versus time for the variety of the coordinates on membranes, temperature versus coordinates at the sensitive layer area’s highest heat value and temperature versus time in the center of the membranes are presented. Recommendations are given for the selection of membrane material for the heat-insulating membrane structure of sensitive elements for semiconductor gas sensors.

Controllable two-membrane-in-the-middle cavity optomechanical system

We report an optomechanical system with two dielectric membranes inside a Fabry-Perot cavity. The cavity resonant frequencies are measured in such a two-membrane-in-the-middle system, which show an interesting band-structure-like diagram. This system exhibits great controllability on the parameters of the system. The positions and angles of each membrane can be manipulated on demand by placing two membranes inside the cavity separately. The eigenfrequencies of the vibrational modes of the membranes can also be tuned individually with piezoelectricity. This scheme could be straightforwardly extended to multiple-membrane-in-the-middle systems, where more than two membranes are involved. Such a well controllable multiple membrane optomechanical system provides a promising platform for studying nonlinear and quantum dynamical phenomena in multimode optomechanics with distinct mechanical oscillators.

Highly sensitive mass detection based on nonlinear sum-sideband in a dispersive optomechanical system.

We present a theoretical scheme to realize high-sensitive mass detection in a dispersive optomechanical system (DOMS) via nonlinear sum-sideband. In this scheme, DOMS assisted by a degenerate parametric amplifier (DPA) provides a well-established optomechanical circumstance, where nonlinear optomechanical interaction between cavity mode and mechanical mode of dielectric membrane is expected for creating the frequency components at optical sum-sideband. Such a scheme for mass detection mainly relies on monitoring the conversion efficiency of generated sum-sideband after the added mass is absorbed on the dielectric membrane. Using experimentally achievable parameters, we find that the conversion efficiency of sum-sideband and the sensitivity of mass detection can be simultaneously improved when the nonlinear gain of DPA increases. Furthermore, our results also demonstrate that this mass detection of DOMS can reach femtogram (fg) level resolution, when the method of mass detection relies on a direct relationship between maximum efficiency of sum-sideband and mass-change of membrane.

High fidelity moving Z-score based controlled breakdown fabrication of solid-state nanopore

We investigate the current transport characteristics in the electrolyte-dielectric-electrolyte structure commonly used in the in situ controlled breakdown (CBD) fabrication of solid-state nanopores. It is found that the stochastic breakdown process could lead to fidelity issues of false positives (an incorrect indication of a true nanopore formation) and false negatives (inability to detect initial nanopore formation). Robust and deterministic detection of initial physical breakdown to alleviate false positives and false negatives is critical for precise nanopore size control. To this end, we report a high fidelity moving Z-score method based CBD fabrication of solid-state nanopore. We demonstrate 100% success rate of realizing the initial nanopore conductance of 3 ± 1 nS (corresponds to size of 1.7 ± 0.6 nm) regardless of the dielectric membrane characteristics. Our study also elucidates the Joule heating is the dominant mechanism for electric field-based nanopore enlargement. Single DNA molecule sensing using nanopores fabricated by this method was successfully demonstrated. We anticipate the moving Z-score based CBD method could enable broader access to the solid state nanopore-based single molecule analysis.

Development, manufacturing, and validation of a dielectric elastomer membrane actuator–driven contactor

Dielectric elastomers represent a relatively new technology with high potentials for actuators’ applications. Thanks to their lightweight, fast operations, energy efficiency, low power consumption, large deformations, and high scalability, dielectric elastomers permit to develop novel mechatronic systems capable of overperforming standard actuation technologies, such as solenoid valves, in several applications. This article presents a novel design for a dielectric elastomer–driven actuator system which enables closing and opening of a contactor. The design is based on a combination between circular out-of-plane dielectric elastomer membranes and a bi-stable biasing system which allows to increase the out-of-plane stroke. Characterization of the contactor is initially performed in order to establish the actuator requirements in terms of force and stroke. Then, systematic design and manufacturing are carried out for both dielectric elastomer membranes and biasing mechanism. Finally, the effectiveness of the actuator in closing and opening the contactor is validated experimentally. The results show comparable dynamic performance to a conventional electromagnetic drive, with the additional advantage of a significantly lower energy consumption.

Light and Flexible Composite Nanofibrous Membranes for High-Efficiency Electromagnetic Absorption in a Broad Frequency.

With the fast advancement of up-to-date communication technologies, electromagnetic wave (EMW) absorption materials are widely required for various applications. However, it is still a big challenge to produce lightweight, flexible, and high-efficiency EMW absorption materials in a broad-ranging frequency. Herein, we designed to fabricate the magnetic and dielectric nanofibrous membranes which can be effectively used as EMW absorption materials by facile electrospinning process. The as-fabricated composite carbon nanofibers (CNFs), which combined the components of nickel, cobalt antioxidant nanoparticles, and carbon nanotubes, exhibited outstanding magnetic and dielectric properties and strong absorption ability in a wide frequency range. These nanoparticles encapsulated in CNFs are extremely beneficial to the electrical conductivity of the composites through decreasing the contact loss within the CNFs by formation of the metal-metal interfaces. Correspondingly, the RL value of -46.60 dB was reached at 4.88 GHz frequency range with a layer thickness of 5.5 mm for these mechanically light and flexible membranes. The enhanced absorption performance (<-10 dB) in the wide frequency band (4.16-18 GHz) can be achieved by selecting a suitable thickness of the material. Results demonstrate that the permittivity and permeability of developed samples have been largely improved because of the integrated interaction of all introduced components in the structure. The composite membranes are a promising candidate for scalable, lightweight, and high-performance EMW absorption materials in the frequency range from C band to Ku band (4-18 GHz).

Dynamic Response and Stability Analysis with Newton Harmonic Balance Method for Nonlinear Oscillating Dielectric Elastomer Balloons

Subject to various pressure and voltage values, the deformation of a hyperelastic dielectric elastomer membrane may attain different stable and unstable equilibria. In this paper, the neo-Hookean material model is adopted to describe the hyperelastic behavior of a dielectric elastomer membrane. The effects of initial stretch ratio, pressure and voltage on the nonlinear free vibration of a spherical dielectric elastomer balloon are investigated qualitatively and quantitatively. Through a linear stability analysis of the equilibrium states, the safe regime of initial stretch ratio for the deformation of dielectric elastomer balloon is confined. Under specific static driving pressure and voltage, the system oscillates about the stable equilibrium and there is no oscillation in the neighborhood of the unstable equilibrium. Besides, the critical pressure and voltage values are determined. Beyond the critical values, there is no periodic oscillation. Along with the stability analysis, complex dynamical behavior such as drastic change of output regime, sporadic instability and sudden bifurcations can be predicted. By applying the Newton Harmonic Balance (NHB) method for quantitative analysis, the frequency response can be readily predicted. It is found that the nonlinear free vibration frequency decreases with increasing initial stretch ratio and control parameters (pressure and voltage).

Advantages of nonlinear energy harvesting with dielectric elastomers

The paper considers electrostatic energy conversion from ambient vibrations using dielectric elastomers. A novel device for vibration energy harvesting is proposed, studied and compared with a vibroimpact device previously investigated by the authors for the same purpose. The nonlinear dynamic behaviour of the new device is explored numerically and the results presented indicate excellent energy harvesting capabilities with an energy density of 9.15 J∕kg. The proposed device particularly benefits from stiffness nonlinearity of its dielectric membranes as is demonstrated by comparison with their linear behaviour. The influence of nonlinearity is further investigated, with results compared against recent reports on dielectric elastomer energy harvesting and other forms of vibration energy harvesting. Two electrical schemes that can be used for the electrostatic energy conversion are also introduced and compared in terms of their suitability for the proposed device.

A computational model of bio-inspired tunable lenses

Bio-inspired tunable lenses are composed of soft dielectric elastomer membranes, clear liquids and rigid frames. Being a new type of optical lens, its focus can be adjusted by the applied voltage. For this type of micro-lens to be practically used in real life, the functional relationship between the voltage and the focus needs to be determined, together with the impact of lens parameters such as the pre-stretching of soft dielectric elastomer membranes, the scale and the volume of liquids on this relationship, as well as on the maximum change of lens focus. In this paper, a compact computational model is proposed based on the assumption of homogeneous deformation and application of energy methods. The model results fit well with the experimental data. By using this model, the relationship curve between the applied voltage and the focus has been given, and it has been verified that such lens will not fail in operation. Finally, by analyzing the three parameters of lens, we can also demonstrate that the pre-stretching of dielectric membranes and the scale affect the relationship between the applied voltage and the focus the most, with the volume of liquids having the least impact.

Quantum correlation and squeezing dynamics of a dissipative nonlinear optomechanical oscillator: Heisenberg-Langevin approach

In this paper, an optomechanical cavity that is quadratically coupled to the cavity field and formed by a micropillar with Bragg reflectors and a thin dielectric membrane, is studied. In addition, it is considered that this interaction occurs in the presence of Kerr medium, external laser field and damping effects (for cavity field and moving Bragg reflector). Using the Heisenberg-Langevin approach, the dynamics of quantum correlation functions (for cavity field and moveable reflector) and squeezing parameters for quadratures of the cavity field are investigated. In each case, the influences of optomechanical coupling, detuning parameter, thermal mean number of cavity photons and phonons, damping parameters and Kerr medium on the above nonclassicality features are analyzed in detail. It is illustrated that the amount of the above-mentioned physical phenomena can be controlled by appropriately choosing the evolved parameters. Also, we show that photon and phonon blockades emerge in some special cases.

Fine tuning the electro-mechanical response of dielectric elastomers

We propose a protocol to model accurately the electromechanical behavior of dielectric elastomer membranes using experimental data of stress-stretch and voltage-stretch tests. We show how the relationship between electric displacement and the electric field can be established in a rational manner from these data. Our approach demonstrates that the ideal dielectric model, prescribing linearity in the purely electric constitutive equation, is quite accurate at low-to-moderate values of the electric field and that, in this range, the dielectric permittivity constant of the material can be deduced from stress-stretch and voltage-stretch data. Beyond the linearity range, more refined couplings are required, possibly including a non-additive decomposition of the electro-elastic energy. We also highlight that the presence of vertical asymptotes in voltage-stretch data, often observed in the experiments just prior to failure, should not be associated with strain stiffening effects but instead with the rapid development of electrical breakdown.

Bioinspired Low-Noise Wing Design for a Two-Winged Flapping-Wing Micro Air Vehicle

This work investigates the acoustic and thrust performances of different wing designs for a two-winged flapping-wing micro air vehicle (FW-MAV). The reference wings, made of a Mylar film membrane supported by carbon-fiber rods, produce a perceived overall noise of about 68.8 dBA when operating at the flapping frequency of 10 Hz typically required for flying such a flapping wing vehicle. This noise is much higher than the value of the environmental background. Wings of various materials and structural configurations are designed and tested in order to reduce the flapping-wing noise. Sound and force measurements are used to assess their acoustic and lift capabilities. It is found that a wing made with a highly elastic dielectric elastomer membrane can reduce the overall perceived noise of the flapping wing by 12 dBA while slightly increasing the thrust. The mechanisms leading to this noise reduction and their potential applications in quiet FW-MAVs are discussed.

Design and Characterization of a Soft Dielectric Elastomer Peristaltic Pump Driven by Electromechanical Load

Pumps are widely used in nature and engineering to transport fluids, particles, and mixtures. Compared to those in engineering, most natural pumps are soft, highly efficient, and reliable. In this paper, we design a soft dielectric elastomer peristaltic pump (DEPP) inspired by the human heart. The DEPP is composed of two pump modules and each module consists of four layers of dielectric elastomer membrane and three layers of carbon grease as electrodes. The two pump modules are driven by two complementary signals with different waveforms including square, sine, sawtooth, and triangular waves. We build a measuring system including pressure and flow rate sensors to characterize the DEPP's performance. The experimental results reveal that the square wave voltage provides the highest flow rate and pressure difference compared to the other three waveforms. The mechanical resonance of DEPP is observed and the optimal frequency with square wave voltage is about 1.5 Hz, which falls in the range of the human heart rate. The optimal frequency decreases with the increase of electromechanical loads. In the experiment, compared with the existing dielectric elastomer pump, we obtain the highest average flow rate and the highest instant flow rate as 2.5 L/min and 3.2 L/min, respectively. The maximum pump volume per cycle for the DEPP is 0.09 L. It takes about 1 s for the DEPP to reach a new equilibrium state when the working frequency of the voltage is switched from 1 to 1.5 Hz. It is hoped that this study will guide the development of new artificial hearts and other soft industrial pumps.

Mechanisms of electromechanical wrinkling for highly stretched substrate-free dielectric elastic membrane

In this work, the electromechanical wrinkling of a highly stretched substrate-free dielectric elastic membrane is theoretically and experimentally studied. Considering the hyperelasticity, anisotropy of the bending stiffness, and electromechanical coupled deformation of the dielectric elastic membrane, a general theoretical model for the wrinkling of a pre-stretched substrate-free membrane is developed. The theoretical model analytically predicts the critical voltage and wavelength of the membrane at the onset of its buckling, which agrees well with the experimental and simulation results. In the post buckling stage, based on Föppl-von Karman stain, the buckling amplitude is analytically derived and coincides with the experiments and simulations as well. The effects of pre-stretching ratio, membrane geometry, electrode thickness, and material property on the critical wrinkle voltage, wrinkle wavelength and electrical breakdown are discussed systematically, based on which a full deformation diagram of the substrate-free membrane under voltage is given. Compared to previous works that interpreted membrane wrinkling simply by the direction change of principle stress (from positive to negative), this work takes a significant step forward to develop theoretical models that can analytically and quantitatively predict the wrinkling wavelength, post-buckling amplitude, and critical wrinkling voltage of the substrate-free membrane. The results herein shed useful insights for the regulation and control of membrane wrinkling which holds potential applications in intelligent structures and devices.

The out-of-plane behaviour of dielectric membranes: Description of wrinkling and pull-in instabilities

Voltage controlled dielectric membranes exhibit two fundamental types of instability, strongly affecting their performances: the occurrence of wrinkling, which is due to membranal compressive stresses, and the onset of pull-in, a catastrophic thinning localisation that preludes electrical breakdown. In this manuscript we provide a unifying energetic description of both instabilities for large, out-of-plane and inhomogeneous deformations. By using the ideas of relaxation and regularisation of the energy, originally proposed by Pipkin (1986) and Hilgers and Pipkin (1992) for purely elastic membranes, we show that the onset and development of wrinkling can be effectively described by the relaxed electroelastic energy. For axially symmetric membranes and neo-Hookean materials, we show that pull-in corresponds to failure of the strong ellipticity condition of the regularised electroelastic energy, thus extending to out-of-plane deformations the validity of a previous estimate for planar systems (Zurlo et al., 2017). In agreement with ubiquitous experimental evidence, we also show that wrinkled states are always stable below the pull-in voltage. Our theoretical findings are assessed by the comparison with experiments on out-of-plane, voltage-actuated annular membranes, showing good agreement both in terms of description of wrinkled states, and for the prediction of the pull-in instability.

Role of dielectric layer and beam membrane in improving the performance of capacitive RF MEMS switches for Ka-band applications

In this paper, we have analyzed the role of dielectric layer and different beam membranes on the performance parameters of shunt capacitive RF MEMS switch. The investigation mainly focused on the major challenges of performance parameters are reducing actuating voltage and improving the isolation. The actuation voltage is reduced by incorporation of non-uniform meanders to the serpentine membrane structure and also improved the isolation using 50 nm AlN dielectric thin film. Here, we have incorporated the holes to the top membrane which help the switch to improve the insertion property. The actuation voltage required to move the switch downwards is 5.4 V and the switch operates at transition time of 12 μs. The isolation − 72.4 dB is observed at the frequency of 27 GHz and insertion − 0.34 dB is observed at the frequency of 27 GHz. The characteristics of switch have been observed by simulating the switch design in FEM tool and results have been compared with theoretical calculations. Finally, the switch is optimized based on the switch performance parameters and it is suitable for Ka-band applications.

Two-membrane cavity optomechanics

We study the optomechanical behaviour of a driven Fabry–Pérot cavity containing two vibrating dielectric membranes. We characterize the cavity mode frequency shift as a function of the two-membrane positions, and report a ∼2.47 gain in the optomechanical coupling strength of the membrane relative motion with respect to the single membrane case. This is achieved when the two membranes are properly positioned to form an inner cavity which is resonant with the driving field. We also show that this two-membrane system has the capability to tune the single-photon optomechanical coupling on demand, and represents a promising platform for implementing cavity optomechanics with distinct oscillators. Such a configuration has the potential to enable cavity optomechanics in the strong single-photon coupling regime, and to study synchronization in optically linked mechanical resonators.

Enhanced quasiparticle lifetime in a superconductor by selective blocking of recombination phonons with a phononic crystal

When quasiparticles in a BCS superconductor recombine into Cooper pairs, phonons are emitted within a narrow band of energies above the pairing energy at 2$\Delta$. We show that a phonon bandgap restricting the escape of recombination phonons from a superconductor can increase the quasiparticle recombination lifetime by more than an order of magnitude. A phonon bandgap can be realized and matched to the recombination energy with a phononic crystal, a periodically-patterned dielectric membrane. We discuss in detail the non-equilibrium quasiparticle and phonon distributions that arise in a superconductor due to a phonon bandgap and a pair-breaking photon signal. Although intrinsically a non-equilibrium effect, the lifetime enhancement in the small-signal regime is remarkably similar to an estimate from an equilibrium formulation. The equilibrium estimate closely follows $\exp(\Omega_{bg}/k_BT_b)$, where $\Omega_{bg}$ is the phonon bandgap energy bandwidth above 2$\Delta$, and $T_b$ is the phonon bath temperature of the coupled electron-phonon system. We discuss the impact of a phononic bandgap on the performance of superconducting devices, and propose a superconducting microwave resonator circuit to measure the enhancement in the quasiparticle lifetime.

A novel dielectric elastomer membrane actuator concept for high-force applications

Dielectric elastomer actuators (DEAs) are known to be lightweight, energy efficient, and scalable in performance. Two well-studied DEA concepts are represented by stacked and membrane DEAs, respectively. The first configuration is known for providing high forces, while the second one results in high strokes. This work proposes a novel design solution, which combines the advantages of both concepts, i.e., high force and stroke, based on a stack of high stroke (3 mm) membrane DEAs. While a single silicone-based DE membrane provides an actuation force on the order of hundreds of mN only, the proposed stacking results into a parallel mechanical connection, which increases the overall force to the double-digit newton range. The biasing mechanism, which is necessary to operate the dielectric elastomer membrane as an actuator, is placed within the passive frame of the DEAs, leading to an overall compact design. To demonstrate the potential of the concept, two prototypes capable of generating record high forces are assembled and tested. The first one allows to lift a weight of 10 kg up to 3 mm, while the second one allows to generate a compression force of 87 N, while working compressing a linear spring with a stiffness of 30.7 N mm−1 up to 2.8mm. These prototypes allow to establish a boosting factor of about 200 for the force output of membrane DEAs.