Showing papers by "Benliang Zhu published in 2018"

The Development of a New Piezoresistive Pressure Sensor for Low Pressures

Abstract: This paper presents the design methodology and fabrication process of a novel piezoresistive pressure sensor with a combined cross-beam membrane and peninsula (CBMP) diaphragm structure for micropressure measurements. The sensor is then analyzed through various experiments. The sensor is primarily designed based on the optimized sensitivity, and a finite-element method is used to predict the stresses that are induced in the piezoresistors and the deflection of the membrane under different pressures. Compared to other traditional diaphragm types, a significant increase in sensitivity can be achieved by the proposed sensor, and the membrane deflection and nonlinearity error considerably decrease. The sensor fabrication process is performed on an n-type single-crystal silicon wafer, and photolithography is used with five masks to fabricate the sensing elements. Additionally, piezoresistors are formed by boron implantation. The experimental results indicate that the fabricated sensor with the CBMP membrane yields a high sensitivity of 25.7 mV/kPa and a low nonlinearity of −0.28% full-scale span for a pressure range of 0–5 kPa at room temperature.

Design of buckling-induced mechanical metamaterials for energy absorption using topology optimization

Abstract: A novel design concept for buckling-induced mechanical metamaterials for energy absorption is presented. The force-displacement curves of the mechanical metamaterials are analyzed according to the curves of their unit cells, and the energy-absorbing characteristics of mechanical metamaterials are evaluated. Two topology optimization models are proposed. One maximizes the buckling-induced dissipated energy to facilitate the design of metamaterials with high energy absorption and low elastic strain energy. The other maximizes the dissipated energy with a constraint that the mechanical metamaterials should be self-recoverable. An energy interpolation scheme is employed to avoid numerical instabilities in the geometric nonlinear finite element analysis. A two-phase algorithm is proposed to find the optimized result from a uniform initial guess, and sensitivity analysis is performed. The optimized design has a larger amount of buckling-induced dissipated energy than the previously proposed structural prototypes. Moreover, the self-recoverable mechanical metamaterial is successfully designed by topology optimization.

Mechanical Structural Design of a Piezoresistive Pressure Sensor for Low-Pressure Measurement: A Computational Analysis by Increases in the Sensor Sensitivity.

Abstract: This paper proposes a novel micro-electromechanical system (MEMS) piezoresistive pressure sensor with a four-petal membrane combined with narrow beams and a center boss (PMNBCB) for low-pressure measurements. The stresses induced in the piezoresistors and deflection of the membrane were calculated using the finite element method (FEM). The functions of the relationship between the dimension variables and mechanical performance were determined based on the curve fitting method, which can provide an approach for geometry optimization of the sensor. In addition, the values in the equations were varied to determine the optimal dimensions for the proposed membrane. Then, to further improve the sensitivity of the sensor, a series of rectangular grooves was created at the position of the piezoresistors. The proposed diaphragm was compared to existing diaphragms, and a considerable increase in the sensitivity and a considerable decrease in nonlinearity error could be achieved by using the proposed sensor. The simulation results suggest that the sensor with the PMNBCB structure obtained a high sensitivity of 34.67 mV/kPa and a low nonlinearity error of 0.23% full-scale span (FSS) for the pressure range of 0⁻5 kPa. The proposed sensor structure is a suitable selection for MEMS piezoresistive pressure sensors.

Structural Topology Optimization Using a Moving Morphable Component-Based Method Considering Geometrical Nonlinearity

Abstract: The moving morphable component (MMC)-based method is a newly developed approach for topology optimization. In the MMC-based method, the design problem is formulated using a set of morphable components, and the optimized structural topologies are obtained by optimizing shapes, sizes, and locations of these components. However, the optimization process often tends to break the connection between the load area and the supported boundary. This disconnection has a strong influence on the convergence, especially when the large deformation effects are considered. In this paper, a method is developed for topology optimization of geometrically nonlinear structures by using the MMC-based method. A scheme is developed to address the disconnection issue in the optimization process. Several numerical examples are used to demonstrate the validity of the proposed method.

Generating ultra-small droplets based on a double-orifice technique

Abstract: Generating individual, small droplets offers unique possibilities for various applications where precise volume and concentration control are necessary. This paper presents a systematic method for generating ultra-small droplets based on a controllable meniscus break-up procedure. The method utilizes two nozzles that are connected to a computer-controlled syringe through a three-way junction. A syringe is used to extrude the liquid from both orifices until they are connected by a liquid meniscus. Next, draining the liquid out of the meniscus and back into the nozzle will cause the meniscus to thin, which will ultimately result in its break-up and the formation of one small droplet. Both experimental and theoretical studies are presented to demonstrate the validity of the proposed method. It is shown that droplets with volumes from femtoliters to nanoliters can be generated.

Topology optimization of fusiform muscles with a maximum contraction.

Abstract: Understanding the optimal designs in nature is critical in bionics. This paper presents a method for designing the configuration of fusiform muscle with a maximum contractile displacement based on topology optimization methods. A nearly incompressible continuum constitutive model of skeletal muscle is utilized. The contractile displacement from the relaxed state to the contracted state is regarded as the objective function. To handle the numerical difficulties that result from the existence of element density, an energy interpolation equation is employed, and a modification of the constitutive model of skeletal muscle is proposed. Several numerical examples are given to demonstrate the reasonability of the proposed method.

Topology Optimization of Compliant Mechanisms Using Moving Morphable Components with Flexure Hinge Characteristic

Abstract: This paper presents a compliant mechanisms synthesis method using moving morphable components (MMC) topology optimization with a view of replacing de facto hinges by specific flexure hinge characteristic. The shape of a common used corner-filleted hinge is embed into the profile of quadratically varying thickness component. The geometric parameters of the hinge is treated as design variables, participate in the optimization process directly. To obtain relatively stable topological configurations in different spring stiffness, keynodes connectivity preservation is applied which can provide a forced connection between components and input, output and fixed ports. The validity of the method is demonstrated using numerical examples.

Topology Optimization of Flexure Hinges with Distributed Stress for Flexure-Based Mechanisms

Abstract: Flexure hinges have been widely used in precision positioning, precision measurement and other fields due to its high-precision features. Traditional notch flexure hinges often exhibit local stress, which limits the range of motion and reduces the fatigue life of flexure-based mechanisms. This paper proposes a conceptual method for designing flexure hinges with distributed stress by using the topology optimization approach. The topology optimization model is developed. The objective function is presented by equally minimizing the ratio of axial displacement and bending displacement and the maximum stress. A global P-norm stress measure is used to reduce the stress level of flexure hinges. The solid isotropic material with penalization (SIMP) is adopted to describing the topology optimization problem. Numerical examples are used to demonstrate the validity of the proposed method.

Multi-steady-state compliant Bricard mechanism and steady-state analysis method thereof

Abstract: The invention discloses a multi-steady-state compliant Bricard mechanism and a steady-state analysis method thereof. The multi-steady-state compliant Bricard mechanism is formed by connecting a plurality of Bricard basic units in an end-to-end manner so as to form an annular closed structure; each Bricard basic unit comprises two flexible hinges and two rigid connecting parts, which the two flexible hinges are provided with different planes orthogonal to each other, and two rigid connecting parts are used for enabling the flexible hinges to be connected; every two flexible hinges are connectedthrough one rigid connecting part; one flexible hinge is connected to one flexible hinge of the adjacent Bricard basic unit through the other rigid connecting part; the two rigid connecting parts inthe same Bricard basic unit have to be equal in length; but the rigid connecting parts of different Bricard basic units do not have to be equal in length. The multi-steady-state compliant Bricard mechanism and the steady-state analysis method thereof have the advantages that the continuous rotation, multiple steady states and the like of a compliant triple Bricard mechanism can be achieved, meanwhile, the mechanism topology is changeable, the unit number is adjustable, and implementation and popularization are easy.

Multistability Analysis for the Compliant Four-Fold Bricard Loops

Abstract: Threefold over-constrained Bricard mechanisms can be widely used in areas such as deployable mechanism, origami mechanism and compliant mechanisms. However, the triangular topology of this structures cannot meet all the practical stresses and have less application flexibility than quadrilateral. This paper presents, models and analyses the compliant multistable four-fold Bricard mechanisms. First, mechanism prototype is analyzed, including the DOF analysis, the kinematics model and the kinematics relationship. Second, multistable behaviors of the proposed mechanism are analyzed using a energy related method. At last, prototype devices and potential applications are prospected for the proposed Bricard loops.