3D Cavity Research Articles

Numerical investigations of the development and suppression of the natural convection flow and heat transfer in the presence of electromagnetic force

In this article, a set of parametric studies is performed to establish the optimum configuration of magnetic field strength and its orientation for enhancement in the convection heat transfer. The present numerical analysis reveals the significance of magnetic field and its orientation on the natural convection flow and heat transfer in the 3D cavity at a fixed Rayleigh number (Ra) of 106 and Prandtl number (Pr) of 0.025. The governing partial differential equations consist of continuity, momentum and energy equations coupled along with the Maxwell's electrodynamics equations using OpenFOAM. The unsteady flow in the transitional zone is regulated and suppressed back to the steady-state region by the presence of the magnetic field imposed in x- (Bx), y- (By) and z-direction (Bz). The magnetic field strength is varied by changing the Hartmann number (Ha) in the range of 0 - 200. It is observed that the Bz magnetic field suppressed the undulation in the flow without suppressing the convection current in the enclosure compared to Bx and By magnetic fields, hence, regulating the convection heat transfer. The strength and orientation of the Lorentz force govern the suppression or regulation of flow patterns in the enclosure. The pertinent quantities such as time-averaged Nusselt number (Nuavg) over the hot surface, streamline variations, electric potential distributions, electric current variations, Lorentz force contours, velocity variations (Ux and Uy), and temperature isosurfaces are discussed in detail.

Three-dimensional lattice Boltzmann flux solver for simulation of fluid-solid conjugate heat transfer problems with curved boundary.

A three-dimensional (3D) lattice Boltzmann flux solver is presented in this work for simulation of fluid-solid conjugate heat transfer problems with a curved boundary. In this scheme, the macroscopic governing equations for mass, momentum, and energy conservation are discretized by the finite-volume method, and the numerical fluxes at the cell interface are reconstructed by the local solution of lattice Boltzmann equation. For solving the 3D fluid-solid conjugate heat transfer problems, the density distribution function (D3Q15 model) is utilized to compute the numerical fluxes of continuity and momentum equations, and the total enthalpy distribution function (D3Q7 model) is introduced to calculate the numerical flux of the energy equation. The connections between the macroscopic fluxes and the local solution of the lattice Boltzmann equation are provided by the Chapman-Enskog expansion analysis. As compared with the lattice Boltzmann method, in which the time step and grid spacing are correlated, the local solution of the lattice Boltzmann equation at each cell interface used in the present scheme is independent of each other. As a result, the drawback of the tie-up between the time step and grid spacing can be effectively removed and the developed method applies very well to nonuniform mesh and curved boundaries. To validate the performance of the developed method, the steady and unsteady natural convection in a finned 3D cavity and in a finned 3D annulus are simulated. Numerical results showed that the present scheme can effectively solve the 3D conjugate heat transfer problems with a curved boundary.

Chaotic photon spheres in non-Euclidean billiard

Abstract With the advancement in understanding of the physics inside chaotic systems, chaos has been harnessed from a nuisance to a beneficial factor in optical devices. Light–matter interaction in chaotic systems has been utilised for improving broadband energy harvesting and momentum transformations, achieving light localization beyond diffraction limit and even stabilizing the dynamics of high power laser. While extensive study about wave chaos has been made in deformed microcavities, investigation of how chaos dynamics evolves in curved space manifold remains elusive. Here, we study the non-Euclidean billiard of a torus-like manifold, which is a closed 2D cavity system with effective periodic boundaries. The ray chaotic behaviours on the deformed toroidal surface are explored using the geodesic equation. By tuning the deformation parameter of the torus, we observe the transition of the billiard from the ordered phase state to mixed phase states and then complete ray chaos. The photon sphere of the torus is identified as the transition position from ordered states to chaotic states. Compared with other chaotic behaviours resulted from the random scattering inside deformed cavities, we demonstrate chaotic dynamics purely on a curved surface, which may shed light on the better understanding of chaos in optics.

Wavelength transduction from a 3D microwave cavity to telecom using piezoelectric optomechanical crystals.

Microwave-to-optical transduction has received a great deal of interest from the cavity optomechanics community as a landmark application for electro-optomechanical systems. In this Letter, we demonstrate a novel transducer that combines high-frequency mechanical motion and a microwave cavity for the first time. The system consists of a 3D microwave cavity and a gallium arsenide optomechanical crystal, which has been placed in the microwave electric field maximum. This allows the microwave cavity to actuate the gigahertz-frequency mechanical breathing mode in the optomechanical crystal through the piezoelectric effect, which is then read out using a telecom optical mode. The gallium arsenide optomechanical crystal is a good candidate for low-noise microwave-to-telecom transduction, as it has been previously cooled to the mechanical ground state in a dilution refrigerator. Moreover, the 3D microwave cavity architecture can naturally be extended to couple to superconducting qubits and to create hybrid quantum systems.

Engineering cross resonance interaction in multi-modal quantum circuits

The existing scalable superconducting quantum processors have only nearest-neighbor coupling. This leads to a reduced circuit depth, requiring a large series of gates to perform an arbitrary unitary operation in such systems. Recently, multi-modal devices have been demonstrated as a promising candidate for small quantum processor units. Always on longitudinal coupling in such circuits leads to implementation of native high fidelity multi-qubit gates. We propose an architecture using such devices as building blocks for a highly connected larger quantum circuit. To demonstrate a quantum operation between such blocks, a standard transmon is coupled to the multi-modal circuit using a 3D bus cavity giving rise to small exchange interaction between the transmon and one of the modes. We study the cross-resonance interaction in such systems and characterize the entangling operation and the unitary imperfections and crosstalk as a function of device parameters. Finally, we tune up the cross-resonance drive to implement multi-qubit gates in this architecture.

Application of the local RBF collocation method to natural convection in a 3D cavity influenced by a magnetic field

This paper explores, for the first time, the application of the novel mesh-free local radial basis function collocation method (LRBFCM) to the solution of a multi-physics problem in three dimensions. A related benchmark problem is solved by considering the natural convection of an incompressible Newtonian fluid in a differentially heated cubic cavity with and without the application of a magnetic field. The research is limited to typical magnetic fields used in the magnetohydrodynamic processing of liquid metals. For this purpose the assumption of small magnetic Reynolds numbers Rem ≪ 1 is made. Spatial discretization is performed by local non-uniform collocation with scaled multiquadrics radial basis functions (RBFs) with the shape parameter set to a constant value and the explicit Euler formula used to perform the time stepping. The involved temperature, velocity and pressure fields are represented on overlapping seven-nodded sub-domains. The pressure-velocity coupling is resolved by the fractional step method. The originality of the contribution represents LRBFCM solution of the classic three-dimensional steady natural convection benchmark for Rayleigh numbers from 105 to 107 and Prandtl number 0.71, and its extension to Prandtl number 0.1, and Hartman numbers 0, 10, 50 and 100. The accuracy of the LRBFCM is found to be comparable with the published benchmark results obtained using established numerical methods.

Predicting the unsteady states of 2D and 3D lid-driven cavities induced by a centrally located circle and sphere

This investigation addresses a systematic numerical method based on the finite volume method and a full multigrid technique to study two-dimensional and three-dimensional flow of an incompressible fluid inside a cavity driven by the motion of the upper lid. Quantitative aspects of two and three dimensional flows in lid-driven cavities are analyzed by encompassing descriptive Reynolds numbers Re bounded by 1000 and 8000 for 2D case, 100 and 1000 for 3D case. Furthermore, the effects of inner spherical shape on fluid flow characteristics have been also investigated. An analysis of the flow evolution demonstrates that, by further increasing Reynolds beyond a certain critical value, the steady flow becomes unstable and bifurcates to the unsteady flow. Results show that the transition to the unsteady regime follows the classical scheme of a Hopf bifurcation, giving rise to a perfectly periodic state. Flow periodicity has been verified through time history plots for the velocity component and phase-space trajectories as a function of Reynolds number for both cases 2D and 3D. It is also concluded that for 2D and 3D configurations, whether the cavity is obstructed or non-obstructed, the refinement of the grid accelerates the appearance of the unsteady regime and delays it in the opposite case. A one-to-one comparison results between a cavity induced by a centrally located inner shape (a sphere for the 3D case and a circle for the 2D case) and a cavity without an inner shape confirms that by using a grid size 642 for the 2D case or 803 for the 3D case, critical Reynolds number for a cavity with an inner shape are less than that without an inner shape. Whilst, for the grid sizes 1282 and 2562 (2D case) the opposite phenomena occurs and it can be inferred that a bidimensional cavity with an inner circle at the center has a critical Reynolds number higher than that without an inner circle. Hence, the unsteadiness is delayed in this case.

A tunable high-Q millimeter wave cavity for hybrid circuit and cavity QED experiments

The millimeter wave (mm-wave) frequency band provides exciting prospects for quantum science and devices since many high-fidelity quantum emitters, including Rydberg atoms, molecules, and silicon vacancies, exhibit resonances near 100 GHz. High-Q resonators at these frequencies would give access to strong interactions between emitters and single photons, leading to rich and unexplored quantum phenomena at temperatures above 1 K. We report a 3D mm-wave cavity with a measured single-photon internal quality factor of 3×107 and mode volume of 0.14×λ3 at 98.2 GHz, sufficient to reach strong coupling in a Rydberg cavity quantum electrodynamics system. An in situ piezotunability of 18 MHz facilitates coupling to specific atomic transitions. Our unique, seamless, and optically accessible resonator design is enabled by the realization that intersections of 3D waveguides support tightly confined bound states below the waveguide cutoff frequency. Harnessing the features of our cavity design, we realize a hybrid mm-wave and optical cavity, designed for interconversion and entanglement of mm-wave and optical photons using Rydberg atoms.

Effects of self-propulsion, chirality and noise-correlation on the entropic stochastic resonance of an active Brownian particle

Entropic stochastic resonance (ESR) of an active Brownian particle (ABP) confined in two kinds of 2D cavities is investigated. The chirality and self-propulsion, which represent two vital characteristic features of the ABP, can enhance and suppress the ESR monotonously. Novelty, in the absence of the translational noises, the ESR can be induced by the rotational noise solely on condition that the rotational frequency is large enough. Moreover, the ESR can be detected more easily with increasing noise-correlation. This research is expected to provide a theoretical basis for controlling the ABP in confined spaces.

Impacts of non-homogeneous nanofluid approach and orientation angle on convection heat transfer within a 3D wavy cavity

Steady laminar natural convection and heat transfer inside a tilted 3D wavy cavity filled by water-Al2O3 nanofluid does examined numerically by applying the finite element technique. An isothermal curved heater is located at the right surface of the chamber while the left surface remains in a steady cold temperature. The top and bottom horizontal surfaces (top and bottom) are held adiabatic. The governing equations are formulated in the non-dimensional model using the two-component non-homogeneous equilibrium model through transporting phenomena in nanofluids connecting among the influences of Brownian diffusion and thermophoresis. The results of the dimensionless buoyancy-driven parameter, inclination angle, nanoparticle volume fraction and number of undulations were examined. It is shown that the inclination angle, the wavy shape of the surface plus the features of nanofluid are outstanding control parameters to the rate of the heat transfer and the distribution of the fluid flow.

Self-assembled conjoined-cages

A self-assembled coordination cage usually possesses one well-defined three-dimensional (3D) cavity whereas infinite number of 3D-cavities are crafted in a designer metal-organic framework. Construction of a discrete coordination cage possessing multiple number of 3D-cavities is a challenging task. Here we report the peripheral decoration of a trinuclear [Pd3L6] core with one, two and three units of a [Pd2L4] entity for the preparation of multi-3D-cavity conjoined-cages of [Pd4(La)2(Lb)4], [Pd5(Lb)4(Lc)2] and [Pd6(Lc)6] formulations, respectively. Formation of the tetranuclear and pentanuclear complexes is attributed to the favorable integrative self-sorting of the participating components. Cage-fusion reactions and ligand-displacement-induced cage-to-cage transformation reactions are carried out using appropriately chosen ligand components and cages prepared in this work. The smaller [Pd2L4] cavity selectively binds one unit of NO3−, F−, Cl− or Br− while the larger [Pd3L6] cavity accommodates up to four DMSO molecules. Designing aspects of our conjoined-cages possess enough potential to inspire construction of exotic molecular architectures.

Impact of a rotating cone on forced convection of Ag–MgO/water hybrid nanofluid in a 3D multiple vented T-shaped cavity considering magnetic field effects

Forced convection of hybrid Ag–MgO/water nanofluid in a three-dimensional T-shaped vented cavity with multiple ports under the effects of a inner rotating cone and magnetic field is numerically studied with finite volume method. The simulation is performed for various values of parameters such as: Reynolds number (between 100 and 1000), Hartmann number (between 0 and 60), angular velocity of the rotating cone (between − 200 rad/s and 0), aspect ratio of the circular cylinders of the base of the cone (between 0.5 and 2) and nanoparticle solid volume fraction of the hybrid nanofluid ( $$\phi _1$$ between 0 and 0.01, $$\phi _2$$ between 0 and 0.01). It was observed that the average heat transfer rate rises with higher values of Reynolds number, Hartmann number above a specified value, angular rotational speed of the cone, aspect ratio of the cone for values above 1 and solid nanoparticle volume fractions of the hybrid particles. In total, 61% of average heat transfer enhancement for left horizontal upper surface is achieved with the imposed magnetic field. The enhancement in the average Nusselt numbers is 25.6% for the rotating cone at the highest angular velocity as compared to a motionless one. The average heat transfer increases almost linearly with hybrid solid nanoparticle volume fraction, while 8.96% and 15.52% enhancements are obtained for varying the solid volume fraction of the particles with the lower and higher thermal conductivity up to 0.01.

Numerical study on convective flow and heat transfer in 3D inclined enclosure with hot solid body and discrete cooling

Purpose This study aims to deal the numerical simulation on buoyant convection and energy transport in an inclined cubic box with diverse locations of the heater and coolers. Design/methodology/approach The left/right walls are cooled partially whereas the other walls are kept adiabatic. In the left/right walls, three different locations of the cooler are examined, whereas heater moves in three locations in the middle of the enclosed box. The governing models are numerically solved using the finite-element method. Findings The simulations are done on several values of the Rayleigh number and cavity inclination angles and different locations of the heater and coolers. The results are presented in the form of streamlines, isosurfaces and Nusselt numbers for different values of parameter involved here. It is recognized that the inclination of the box and the locations of the coolers strongly influence the stream and energy transport inside the enclosed domain. Research limitations/implications The present investigation is conducted for steady, laminar, three-dimensional natural convective flow in a box for different locations of cooler and tilting angles of a cavity. The study might be useful to the design of solar collectors, room ventilation systems and electronic cooling systems. Originality/value This work examines the effects of different locations of cooler and tilting angles of a cavity on convective heat transfer in a 3D cavity. The study is useful for thermal engineering applications.

Manufacturing and Characterization on aThree-Dimensional Random Resonator of Porous Silicon/TiO2 Nanowires for Continuous Light Pumping Lasing of Perovskite Quantum Dots

In recent years, all inorganic bismuth lead-halide perovskite nanocrystals [CsPbX3 (X[Formula: see text][Formula: see text][Formula: see text]Cl, Br, I)] have received extensive attention due to their high performance in fluorescence quantum yield, narrow emission spectrum, and adjustable emission range. However, the disadvantages of high cost and poor stability have greatly limited the development prospects of the material. Here, in order to develop a perovskite quantum dot lasing cavity with high chemical stability, high quality factor and low fabrication cost, we have successfully fabricated a 3D random cavity device based on porous silicon/TiO2 nanowires. A TiO2 nanowire is grown on the porous silicon to form a 3D resonant cavity, and a perovskite quantum dot is spin-coated on the surface of the 3D resonant cavity to form a novel 3D complex film. The novel structure enhances the chemical stability and lasing quality factor of the resonant cavity while the fluorescence generated by the large quantum dots in the spatial interference structure constitutes the feedback loop, which will provide favorable support for the development of information optics.

III-nitride photonic cavities

Abstract Owing to their wide direct bandgap tunability, III-nitride (III-N) compound semiconductors have been proven instrumental in the development of blue light-emitting diodes that led to the so-called solid-state lighting revolution and blue laser diodes that are used for optical data storage. Beyond such conventional optoelectronic devices, in this review, we explore the progress made in the past 15 years with this low refractive index material family for the realization of microdisks as well as 2D and 1D photonic crystal (PhC) membrane cavities. Critical aspects related to their design and fabrication are first highlighted. Then, the optical properties of passive PhC structures designed for near-infrared such as their quality factor and their mode volume are addressed. Additional challenges dealing with fabrication pertaining to structures designed for shorter wavelengths, namely the visible to ultraviolet spectral range, are also critically reviewed and analyzed. Various applications ranging from second and third harmonic generation to microlasers and nanolasers are then discussed. Finally, forthcoming challenges and novel fields of application of III-N photonic cavities are commented.

Superconducting-circuit based Aulter-Towns splitting effect

The superconducting quantum bit(qubit) based on Josephson junction is a macroscopic artificial atom. The basic parameters of the artificial atom can be changed by micro and nano machining. The three-dimensional (3D) Transmon qubit is a kind of qubit with the longer decoherence time. It is coupled with a 3D superconducting cavity by means of capacitance. It is a man-made coupling system between atom and cavity field, which can verify the effects of atomic physics, quantum mechanics, quantum optics and cavity quantum electrodynamics. In this paper, transmon qubits are prepared by the double angle evaporation method, and coupled with aluminum based 3D superconducting resonator to form 3D transmon qubits. The basic parameters of 3D transmon are characterized at an ultra-low temperature of 10 mK. The 3D transmon parameters are <i>E</i><sub>C</sub> = 348.74 MHz and <i>E</i><sub>J</sub> = 11.556 GHz. The coupling coefficient <i>g</i><sup>2</sup>/<i>Δ</i> between qubit and the 3D cavity is 43 MHz, which is located in the dispersive regime. The first transition frequency of qubit is <i>f</i><sub>01</sub><italic/> = 9.2709 GHz, and the second transition frequency is <i>f</i><sub>12</sub> = 9.0100 GHz. The 3D resonator is made of the material 6061T6 aluminum, the loaded quality factor is 4.8 × 10<sup>5</sup>, and the bare frequency of the resonator is 8.108 GHz. The Jaynes-Cummings readout method is used to find the optimal readout power to distinguish among the qubit in the ground state <inline-formula><tex-math id="M1">\begin{document}$ \left| {\rm{0}} \right\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="23-20200796_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="23-20200796_M1.png"/></alternatives></inline-formula>, qubit in the superposition state of <inline-formula><tex-math id="M2">\begin{document}$ \left| {\rm{0}} \right\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="23-20200796_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="23-20200796_M2.png"/></alternatives></inline-formula> and <inline-formula><tex-math id="M3">\begin{document}$ \left| {\rm{1}} \right\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="23-20200796_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="23-20200796_M3.png"/></alternatives></inline-formula>, and qubit in the superposition state of <inline-formula><tex-math id="M4">\begin{document}$ \left| {\rm{0}} \right\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="23-20200796_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="23-20200796_M4.png"/></alternatives></inline-formula>, <inline-formula><tex-math id="M5">\begin{document}$ \left| {\rm{1}} \right\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="23-20200796_M5.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="23-20200796_M5.png"/></alternatives></inline-formula> and <inline-formula><tex-math id="M6">\begin{document}$ \left| {\rm{2}} \right\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="23-20200796_M6.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="23-20200796_M6.png"/></alternatives></inline-formula>. Then, the Aulter-Townes splitting (ATS) experiment can be fulfilled in this system. Unlike the method given by Novikov et al. [Novikov S, Robinson J E, Keane Z K, et al. 2013 <i>Phys. Rev. B</i> <b>88</b> 060503], our method only needs to apply continuous microwave excitation signal to the qubit, and does not need to carry out precise timing test on the qubit, thus reducing the test complexity of observing ATS effect. The ATS effect in resonance and non-resonance regime are observed. In the resonance ATS experiment, in order to obtain the peak value and frequency of resonance peak, Lorentz curve can be used for fitting peaks, and the ATS curve of double peak can be fitted by adding two Lorentz curves together. In the non-resonance ATS experiment, the detection signal is scanned, and the ATS double peak will shift with the different coupling signal detuning, forming an anti-crossing structure. The two curves formed by crossing free structure give two eigenvalues of Hamiltonian. By solving the equation, the experimental results can also be found to be consistent with the theoretical results.

Three-dimensional transmon coherence measurement method based on network analyser

<sec>Three-dimensional(3D) transmon is a kind of superconducting qubit with long decoherence time, which has important applications in superconducting quantum computation, quantum optics, cavity quantum electrodynamics, et al. Rabi oscillation is a vital method to characterize the decoherence time of quantum system, and it is also a basic experiment to demonstrate the energy level evolution of quantum system. In order to test the Rabi oscillation of 3D transmon, strict timing control is necessary, and the process of testing and debugging is complicated. In this paper, 3D transmon samples are fabricated and their basic parameters <i>E<sub>C</sub></i> = 348.74 MHz and <i>E<sub>J</sub></i> = 11.556 GHz are tested and characterized. The coupling coefficient <i>g<sup>2</sup></i>/Δ between qubit and the 3D cavity is 43 MHz, which is located in the dispersive regime. The qubit’s first transition frequency <i>f</i><sub>01</sub><italic/> = 9.2709 GHz, and the second transition frequency <i>f</i><sub>12</sub> = 9.0100 GHz. The 3D resonator is fabricated by the material 6061T6 aluminum, the loaded quality factor is 4.8 × 10<sup>5</sup>, and the bare frequency of the resonator is 8.108 GHz.</sec><sec>Through comparison, it is found that the Rabi oscillation time obtained by the proposed method is shorter than by the Jaynes-Cummings method. The main reasons are as follows. First, the measurement of network analyzer is a continuous measurement, and the test signal always affects the decoherence process of 3D transmon. Second, the quantum bit is in the ground state after decoherence, and the ground state measured by the network analyzer accounts for a relatively high proportion, which causes the curve measured by the network analyzer to be one-sided attenuation oscillation. Third, the dispersive readout method is related to the quality factor of the superconducting cavity. The storage time of microwave photons in the superconducting cavity is longer than the decoherence time of 3D transmon, so the quantum information is partially decohered before leaving the superconducting cavity, which will shorten the Rabi oscillation time.</sec><sec>An innovative Rabi oscillation test method based on network analyzer is presented. The test system based on this method is simple to build and can be used as a new way to quickly verify whether 3D transmon has quantum characteristics. This method can also be extended to other quantum systems for preliminarily verifying the time domain characteristics.</sec>

A long-lived capacitively shunted flux qubit embedded in a 3D cavity

We report the experimental realization of a 3D capacitively shunt superconducting flux qubit with long coherence times. At the optimal flux bias point, the qubit demonstrates energy relaxation times in the range of 60–90 μs and a Hahn-echo coherence time of about 80 μs, which can be further improved by dynamical decoupling. Qubit energy relaxation can be attributed to quasiparticle tunneling and unwanted two-level-system defects, while qubit dephasing is caused by flux noise away from the optimal point. Our results show that 3D c-shunt flux qubits demonstrate improved performance over other types of flux qubits, which is advantageous for applications such as quantum magnetometry and spin sensing.

Encapsulation and Release of Recognition Probes Based on a Rigid Three-Dimensional DNA "Nanosafe-box" for Construction of a Electrochemical Biosensor.

Herein a rigid three-dimensional (3D) DNA "nanosafe-box" (DNB) for encapsulation and release of a recognition probe (N3) is designed to construct an electrochemical biosensor with the use of electroactive two-dimensional metal-organic framework (2D MOF) nanosheets as signal tags for ultrasensitive detection of mercury ion (Hg2+). Initially, N3 is locked in the 3D cavity of DNB by blocker DNA. After addition of target Hg2+, exonuclease III (Exo-III) digestion is initiated to the liberate DNA "key" (K); thereby, the free K triggers a strand displacement reaction for exposing the prelocked N3 to successfully ligate dibenzocyclooctyne (DBCO)-tagged anchor via metal-catalyst-free click chemistry, in which amounts of 2D MOF nanosheets containing Co(II) as electron mediator are introduced accompanied by significant electrochemical response. Compared with traditional linear or stem-loop DNA nanostructure, the well-designed 3D DNB possesses remarkably enhanced mechanical rigidity and structural stability, resulting in improved accessibility of probes and increased loading amounts of signal tags. More importantly, by this way of encapsulation and release of recognition probes, the background signal is decreased dramatically, leading to increased sensitivity of the proposed biosensor. Consequently, this electrochemical biosensor exhibits outstanding analytical performance for Hg2+ detection with a low detection limit of 33 fM and dynamic linear range of 0.1 pM to 10 nM. This strategy offers an ingenious method for detection of metal ions and biomarkers, possessing potential applications in environmental tests and clinical diagnosis.

Piezo-optomechanical coupling of a 3D microwave resonator to a bulk acoustic wave crystalline resonator

We report the observation of coupling between a 3D microwave cavity mode and a bulk mechanical resonator mediated by piezoelectric and radiation pressure effects. The system is composed of a quartz bulk acoustic wave resonator placed inside a microwave re-entrant cavity, which is designed to act as both the electrodes for piezoelectric actuation and a 3D resonator. The cavity electromagnetic mode is modulated by a 5 MHz bulk acoustic wave shear mode, which is modeled and experimentally verified using the input-output formalism. Through finite element method simulations, we calculate the various contributions to the electromechanical coupling and discuss the potential of the system to reach high cooperativities as well as suitable applications.