Opto Electro Mechanical Systems Research Articles

A new method for reconstructing the 3D shape of single cells in fruit

Fruit cells’ shape generally reflects the physiological state and quality of the fruit, and indirectly dictates its economics. In this study, a new bio-microscope including three independent and orthogonal channels of opto-electromechanical microscopic observation systems was developed to obtain the three views (e.g., front view, top view, side view) of a single fruit cell using tomato and strawberry at two ripening stages as fruit samples. The obtained three-view images were used to reconstruct the 3D real shape of a single cell based on the 3D geometrical modelling method using Solidworks CAD design software and then compared with the actual geometric size. The average relative errors for the major diameter, minor diameter 1, minor diameter 2, projection perimeter and projection area were 4.04 %, 6.25 %, 5.71 %, 1.69 % and 3.79 %, respectively. This good accuracy makes the newly developed bio-microscope together with the proposed 3D geometrical modelling method a promising 3D shape reconstruction technology for a single fruit cell to extract real and detailed cell morphology information. Furthermore, this method can find applications in other fields such as human and animal cells where soft particles’ 3D shape analysis is important.

Reliability-based topology optimization with stochastic heterogeneous microstructure properties

With advanced manufacturing processes, many modern structural designs need to include microscale uncertainties of material properties and microstructures that can affect overall performances, such as microelectromechanical systems, micro–opto–electro–mechanical systems, and micro-optical electronics systems. Topology design optimization at this scale must consider uncertainties from material microstructures as the scale of the structure and material microstructure is comparable. Very few studies consider microstructure uncertainties in topology design due to their scales are much different in classical mechanical/civil engineering. A novel framework of reliability-based topology optimization is proposed to specifically address this gap for the design. The microscale uncertainties of heterogeneous materials are quantified by the explicit mixture random field model. Then, the material distribution is optimized by a heuristic updating scheme, and sensitivities of reliability constraints are calculated using the adjoint design-point-based importance sampling method. The proposed methodology simultaneously considers microscale hierarchical uncertainties in microstructures and material property variations for each phase. The feasibility of the framework is demonstrated by several numerical examples with different multi-phase materials. Compared with deterministic topology optimization and classical topology optimization with first-order reliability method approximations, the optimal design obtained from the proposed method can achieve accurate target reliability with minimized limit state function evaluations.

Quantitative measurement and mechanism analysis of the high-efficiency laser propulsion of a graphene sponge.

Laser propulsion of a graphene sponge shows tremendous potential in propellant-free flight, photoresponsive actuators and micro opto-electro mechanical systems. However, the mechanism is still in dispute and the propulsion force hasn't been accurately measured, seriously hindering its development. This work develops a quantitative method to measure the propulsion force. It is found that the characteristics of the force agree qualitatively with the Knudsen force due to laser-induced thermal nonequilibrium in rarefied gas, which might be another possible mechanism of laser propulsion of a graphene sponge. Also, this kind of laser propulsion is highly efficient, stable and sustainable.

Spatially Adiabatic Frequency Conversion in Optoelectromechanical Arrays.

Faithful conversion of quantum signals between microwave and optical frequency domains is crucial for building quantum networks based on superconducting circuits. Optoelectromechanical systems, in which microwave and optical cavity modes are coupled to a common mechanical oscillator, are a promising route towards this goal. In these systems, efficient, low-noise conversion is possible using a mechanically dark mode of the fields, but the conversion bandwidth is limited to a fraction of the cavity linewidth. Here, we show that an array of optoelectromechanical transducers can overcome this limitation and reach a bandwidth that is larger than the cavity linewidth. The coupling rates are varied in space throughout the array so that the mechanically dark mode of the propagating fields adiabatically changes from microwave to optical or vice versa. This strategy also leads to significantly reduced thermal noise with the collective optomechanical cooperativity being the relevant figure of merit. Finally, we demonstrate that the bandwidth enhancement is, surprisingly, largest for small arrays; this feature makes our scheme particularly attractive for state-of-the-art experimental setups.

High bandwidth on-chip capacitive tuning of microtoroid resonators.

We report on the design, fabrication and characterization of silica microtoroid based cavity opto-electromechanical systems (COEMS). Electrodes patterned onto the microtoroid resonators allow for rapid capacitive tuning of the optical whispering gallery mode resonances while maintaining their ultrahigh quality factor, enabling applications such as efficient radio to optical frequency conversion, optical routing and switching applications.

Controllable optical response in hybrid opto-electromechanical systems**Project supported by the National Natural Science Foundation of China (Grant Nos. 11304110 and 11174101), the Natural Science Foundation of Jiangsu Province, China (Grant Nos. BK20130413 and BK2011411), the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Grant No. 13KJB140002).

We theoretically investigate the analog of electromagnetically induced absorption and parametric amplification in a hybrid opto-electromechanical system consisting of an optical cavity and a microwave cavity coupled to a common mechanical resonator. When the two cavity modes are driven by two pump fields, a weak probe beam is applied to the optical cavity to monitor the optical response of the hybrid system, which can be effectively controlled by adjusting the frequency and power of the two pump fields. We find that the analog of electromagnetically induced absorption and parametric amplification can appear in the probe transmission spectrum when one cavity is pumped on its red sideband and another is pumped on its blue sideband. These phenomena can find potential applications in optical switching and signal amplification in the quantum information process.

Mechanical switch for state transfer in dual-cavity optomechanical systems

Dual-cavity optoelectromechanical systems (OEMS) are those where two electromagnetic cavities are connected by a common mechanical spring. These systems have been shown to facilitate high-fidelity quantum-state transfer from one cavity to another. In this paper, we explicitly calculate the effect on the fidelity of state transfer when an additional spring is attached to only one of the cavities. Our quantitative estimates of loss of fidelity highlight the sensitivity of a dual-cavity OEMS when it couples to additional mechanical modes. We show that this sensitivity can be used to design an effective mechanical switch for inhibition or high-fidelity transmission of quantum states between the cavities.

Phonon-mediated electromagnetically induced absorption in hybrid opto-electromechanical systems

We predict the existence of the electromagnetically induced absorption (EIA) in the double cavity configurations of the hybrid opto-electro mechanical systems (OEMS). We discuss the origin of the EIA in OEMS which exhibit the existence of an absorption peak within the transparency window. We provide analytical results for the width and the height of the EIA peak. The combination of the EIT and EIA is especially useful for photon switching applications. The EIA that we discuss is different from the one originally discovered by Lezama et al in atomic systems and can be understood in terms of the dynamics of three coupled oscillators (rather than two) under different conditions on the relaxation parameters. The EIA we report can also be realized in metamaterials and plasmonic structures.

A superhigh-frequency optoelectromechanical system based on a slotted photonic crystal cavity

We develop an all-integrated optoelectromechanical system that operates in the superhigh frequency band. This system is based on an ultrahigh-Q slotted photonic crystal (PhC) nanocavity formed by two PhC membranes, one of which is patterned with electrode and capacitively driven. The strong simultaneous electromechanical and optomechanical interactions yield efficient electrical excitation and sensitive optical transduction of the bulk acoustic modes of the PhC membrane. These modes are identified up to a frequency of 4.20 GHz, with their mechanical Q factors ranging from 240 to 1730. Directly linking signals in microwave and optical domains, such optoelectromechanical systems will find applications in microwave photonics in addition to those that utilize the electromechanical and optomechanical interactions separately.

Macrorealism inequality for optoelectromechanical systems

We show how to apply the Leggett-Garg inequality to opto-electro-mechanical systems near their quantum ground state. We find that by using a dichotomic quantum nondemolition measurement (via, e.g., an additional circuit-QED measurement device), either on the cavity or on the nano-mechanical system itself, the Leggett-Garg inequality is violated. We argue that only measurements on the mechanical system itself give a truly unambigous violation of the Leggett-Garg inequality for the mechanical system. In this case, a violation of the Leggett-Garg inequality indicates that physics beyond that of ``macroscopic realism'' is occurring in the mechanical system. Finally, we discuss the difficulties in using unbound nondichotomic observables with the Leggett-Garg inequality.

Hybrid resonant energy harvester integrating ZnO NWs with MEMS for enabling zero-power wireless sensor nodes

This work introduces a novel concept for energy scavenging from ambient vibrations utilizing ZnO nanowires (NWs). This concept relies on the combination into a single device of a resonant element (i.e. an inertial mass suspended by four serpentine springs) and two arrays of NWs grown at both sides of the inertial mass. The NWs can be bent as a result of the resonant motion of the mass. Due to the zigzag-shaped profile of the inertial mass, this bending generates an electric current between the electrodes. This power can be used to supply wireless sensor nodes at the micro and nanoscale level. In addition, this generator can be integrated with other elements that can be achieved by taking advantage of the ZnO NWs and their unique properties such as chemical sensors, optoelectromechanical systems or logic circuits driven by mechanical or optical signals. A detailed fabrication process, containing the NW growth method, is described in this paper. Theoretical calculations and FEM simulations have been performed and show the possibility of using these kinds of devices to scavenge energy from sonic and ultrasonic waves.

Laser Locking and Cavity Manipulation With a Cavity Optoelectromechanical System

Cavity optoelectromechanical systems combine the benefits of ultrasensitive motion transduction and strong mechanical actuation. We demonstrate the potential for photonic applications, implementing a Pound-Drever-Hall laser locking technique and strongly driving another mechanical mode, while remaining locked. The mechanical modes are resonantly excited in a silica microtoroid with a radio-frequency electric field, with the optomechanical coupling then imprinting a modulation on the circulating light and consequently the out-coupled light.

A novel MOEMS pressure sensor: Modelling and experimental evaluation

This paper presents a novel MOEMS (Micro Opto Electromechanical Systems) pressure sensor suitable for localized precision measurements in high temperature environments. The sensor is based on a micromachined Fabry-Perot device (MFPD) that uses a thin film microcantilever beam as the top mirror and a silicon substrate as the bottom mirror of the optical microcavity. The major effect that the viscosity and density of the air surrounding the MFPD have on the viscous damping provides the mechanism for the detection of the pressure. A major advantage of this configuration is that there is no need for a sealed microcavity since the air is trapped by the viscous damping effects. The sensor has been tested up to 90 psi and pressure sensitivities of about 0·04%/psi with a MFPD sensor with a resonant frequency of about 46·7 kHz have been measured.

Fabrication of 3D polymer microstructures using electron beam lithography and nanoimprinting technologies

Recently, with the advancement in bio-MEMS and micro optoelectromechanical systems (MOEMS), 3D microstructures have become increasingly important and efficient fabrication processes are currently being sought. In this paper, a novel 3D fabrication process has been proposed by utilizing the proximity effect of electron beam lithography (EBL) to create 3D microstructures on negative photoresists as the primary molds, which are subsequently transferred to their corresponding negative molds using nanoimprinting lithography (NIL), and to form the final replicas by either electroforming or polymer spin casting to reduce cost. The effect of electron backscattering on the 3D topography is firstly investigated and the relationship among the spatial distribution of electron beam irradiation, the spot size and the dosage level of irradiation is experimentally characterized in SU-8 to establish a dosage kernel distribution function. A mathematical procedure based on linear operation of this kernel function is then proposed to mimic the EBL fabrication process. The subsequent experiments indicate that the predicted surface profiles agree with the experimental results to large extent and the proposed mathematical operations are valid for the purpose of designing the fabrication process. Finally, the SU-8 primary molds are transferred to NEB to form secondary molds via the nanoimprinting process. It shows that the nanoimprinting process can essentially reproduce the shape and geometry of the primary molds. However, due to the nature of polymer-to-polymer contact printing, the elastic restitution of materials induces a slight deviation of the final device size and a further study should be made in the future to minimize such types of error. Although the above problems are reported, nevertheless, the primary experimental results indicate that this proposed fabrication process is capable of creating 3D shape microstructure in the order of 1 µm and should be useful for related optical-, bio- and RF-MEMS applications.

Development of novel optoelectromechanical systems based on "transparent metals" PBG structures

Developed a novel smart optoelectromechanical structure, fabricated using a multilayer, metal-dielectric photonic band gap (PBG) structure. We discuss innovative devices with electrically controllable optical properties that can be used as sensors with optical output signals for applications in harsh or hostile environments (pressure sensors, micro gravimeter, or micro accelerometer) or as optical modulators and optical limiters. Theoretical models of these novel devices together with experimental prototypes have been developed, and characterization of the devices has been performed. Moreover, microelectromechanical devices have been studied for application to this field and are presented. In particular, the problem of realizing highly sensitive accelerometers has been addressed, and it will be shown that the proposed approach allows detecting displacements of a few nanometers.

Key Elements of Biomedical Polymer-based Opto Electro Mechanical Systems for a New Generation of Microscope and Microanalysis Biochips

In this talk, the development of key elements for BioPOEMS (Biomedical Polymer-based Opto Electro Mechanical Systems) will be discussed as a new generation of microscopic and microanalysis biochips. Current BioMEMS (Biomedical Microelectromechanical Systems) technology is in its infancy stage. Just as silicon-based microelectronics technology went through many stages since the late ‘60's, BioMEMS technology will have to overcome many obstacles before becoming a mature industry. The IC industry was made possible by the development of fabrication processes, integration technologies, and design tools. Similarly, the field of BioMEMS must prepare new components with biomaterials and tools for the development of new microsystems, enabling the combination of biological sensors and actuators with the rapidly growing capabilities of bioinformatics.Polymers are not only used in macroscopic systems, but are now increasingly finding use in the microscopic realm such as microfluidic devices. Among the many different classes of polymers, it is the fluoropolymers that provide the most unique material characteristics.

InP-based micromachined Mach-Zehnder interferometer stress sensors

In the field of III–V-based compounds, new functionalities can be reached by integrating micromechanical structures with electro-optical functions, in order to fabricate Micro Opto Electro Mechanical Systems (MOEMS). A possible application is an InP-based integrated optical stress sensor. Such a system is based on a partly suspended waveguide that can be strained under the effect of an external stress. The photoelastic effect induces a phase shift that can be converted into an intensity shift of the signal if the device is configurated as a Mach-Zehnder interferometer. This system can be integrated monolithically with the optical source and the photodetector. The mechanical, photoelastic and optical properties of this structure has been simulated in order to configurate the alloy composition of the epitaxial layers and the geometry of the device. Micromachining processes have been developed in order to realize InP-based suspended microstructures by sacrificial layer etching and bulk micromachining. Preliminary results showed that the optical behaviour of the waveguides is close to the theoretical analysis. Characterisation of the complete interferometer is underway in our group.

Fabrication of InP-based freestanding microstructures by selective surface micromachining

InP-based microstructuring methods are presented with a view to develop micro opto electro mechanical systems (MOEMS). Fabrication parameters and dimensions of the freestanding structures are determined for specific technological constraints (etching selectivities, anisotropy, sticking phenomena). thick InGaAs deformable cantilevers, bridges and membranes have been fabricated by elimination of around -thick InAlAs sacrificial layers. Showing high aspect ratio, smooth surfaces and high accuracy in thicknesses, these microstructures are perfectly suitable for optical applications.