An Ultrasound Transducer by Lead Zirconate Titanate (PZT) Nanofibers

In this paper, we demonstrate Lead zirconate titanate (PZT) nanofibers as a transducer to generate and detect ultrasound acoustic waves. PZT nanofibers with average diameter of 102nm were fabricated by the electrospinning method. The as-fabricated nanofibers were collected and aligned across a 10 μm silicon trench with Au electrodes. After annealing, the device was tested with the pulse/delay method. Two resonant frequencies, 8 MHz and 13MHz, were detected respectively. By using the Hamilton’s principle for coupled electromechanical systems with properly assumed mode shape, the resonant frequency was caudated. Base on the current testing result, a broadband ultrasound transducer was envisioned.

Nonlinear Dynamics of an Imperfect Microbeam Under an Axial Load and Electric Excitation

This study is motivated by the growing attention, both from a practical and a theoretical point of view, toward the nonlinear behavior of microelectromechanical systems (MEMS). We analyze the nonlinear dynamics of an imperfect microbeam under an axial force and electric excitation. The imperfection of the microbeam, typically due to microfabrication processes, is simulated assuming the microbeam to be of a shallow arched initial shape. The device has a bistable static behavior. The aim is that of illustrating the nonlinear phenomena, which arise due to the coupling of mechanical and electrical nonlinearities, and discussing their usefulness for the engineering design of the microstructure. We derive a single-mode-reduced-order model by combining the classical Galerkin technique and the Pade´ approximation. Despite its apparent simplicity, this model is able to capture the main features of the complex dynamics of the device. Extensive numerical simulations are performed using frequency response diagrams, attractor-basins phase portraits, and frequency-dynamic voltage behavior charts. We investigate the overall scenario, up to the inevitable escape, obtaining the theoretical boundaries of appearance and disappearance of the main attractors. The main features of the nonlinear dynamics are discussed, stressing their existence and their practical relevance. We focus on the coexistence of robust attractors, which leads to a considerable versatility of behavior. This is a very attractive feature in MEMS applications. The ranges of coexistence are analyzed in detail, remarkably at high values of the dynamic excitation, where the penetration of the escape (dynamic pull-in) inside the double well may prevent the safe jump between the attractors.

Static Analysis of Electrically Actuated Nano to Micron Scale Beams Using Nonlocal Theory

In this paper, size dependent static behavior of micro and nano cantilevers actuated by a static electric field including deflection and pull-in instability, is analyzed implementing nonlocal theory. Euler-bernoulli assumptions are made to model the relation between deflection of the beam and bending moment. Differential form of the constitutive equation of nonlocal theory is used to find the revised equation for bending moment and substituting in the equilibrium equation of electrostatically actuated beams final nonlinear ordinary differential equation is arrived. Also the boundary conditions for solving the equation are revised and to analyze the size effect better governing equation is nondimetionalized. The one parameter Galerkin method is used to transform this equation to a nonlinear algebraic equation. Arrived algebraic equation is solved utilizing Newton-Raphson method. Size effect on the maximum deflection and deflection shape for various applied voltages is studied. Also effect of beam size on the static pull-in voltage is studied. Results indicate that the dimensionless beam deflection decreases as size decreases while the pull-in voltage increases and specially change of deflection and pull-in voltage is significant for nanobeams.

Electrical Determination of Elastic Modulus of Individual PZT Nanofibers by In Situ SEM

We present an electrical measurement of elastic modulus of single electrospun lead zirconate titanate (PZT) nanofibers under harmonic vibration using in situ scanning electron microscopy (SEM) equipped with a nanomanipulator. The PZT nanofiber was fabricated using an electrospinning process and collected on a silicon substrate with 10 μm trenches. The individual PZT nanofibers were excited with an oscillating electric field applied by a network analyzer and the resonant frequency was observed through the SEM along with the transfer frequency spectra simultaneously. The elastic modulus was calculated as ∼70 GPa from this resonant frequency using Euler-Bernoulli equation.

Using Product Archaeology to Integrate Global, Economic, Environmental, and Societal Factors in Introductory Design Education

Design education has traditionally been incorporated into the engineering curriculum in the junior or senior year through upper level mechanical design courses and capstone design projects. However, there is a general trend in engineering education to incorporate design activities at the freshman and sophomore level. The design aspects of these courses provide a unique opportunity to integrate global, economic, environmental, and societal factors with traditional design considerations. Incorporating these early in an engineering curriculum supports a broad engineering education in accordance with ABET required Outcome h. In this paper we introduce global, economic, environmental, and societal factors into a sophomore level engineering design course using strategies adapted from a Product Archaeology paradigm. Specifically, functional modeling is synthesized with a product dissection platform to create a foundation to demonstrate the broader impacts of engineering design decisions. The effectiveness of using Product Archaeology-based educational strategies to facilitate the learning objectives of Outcome h is evaluated using student surveys taken over a two year period.

Upper Level Engineering Design Instruction Using a Product Archaeology Paradigm

Historically, the teaching of design theory in an engineering curriculum was relegated to a senior capstone design experience. Presently, however, engineering design concepts and courses can be found through the entirety of most engineering programs. Educators have recognized that engineering design provides a foundational platform that can be used to develop educational strategies for a wide array of engineering science principles. More recently, educators have found that product archaeology provides an effective platform to develop scalable learning materials, strategies, and educational innovations across these design courses. In this paper, we focus on the upper level design experience and present a set of innovative strategies aimed at teaching design in a global perspective. Moreover, this approach facilitates meeting the challenging requirements of ABET’s Outcome h. The effectiveness of the strategies is assessed using a benchmark national survey on the Engineer of 2020. Results demonstrate a significant increase in student perception across a number of skill and knowledge areas, which are critical to the next generation of engineers.

Building Bridges for Engineering Education: The Experience of Partnership With Building Industry for Sustainable Solutions

Due to a demand for more sustainability, with as ultimate goal Zero Emission Buildings, building design becomes more complex. Building design transfers from a mainly architect led process into a approach for multi-disciplinary design teams to cope with the growing complexity of the process. A supportive design method was developed in cooperation with the Dutch professional organizations of architects and consulting engineers. The design method provides overview and helps to structure the communication and reflection between design team members. The design method is focused on sustainability and the creation of sustainable solutions in the conceptual phase of building design. After testing the method in workshops as part of a training program in industry, the design method was transferred and applied at the department of architecture for master students for their multidisciplinary Master project Integral Design. The workshops became part of the permanent professional education program of the Dutch society of architects, several in-company workshops for industry were held and a course is now being developed for the Dutch society of building services engineers. So the partnership with building industry let to the developed design support method which acted as a kind of bridge for engineering education.

3-Dimensional Force Curve and Dissipation Model Acquisition Using the Spectral Inversion Method in Tapping Mode AFM

Atomic force microscopy (AFM) has been a field driving at exploring nanoscale surfaces and measuring both topography as well as material properties. One of the phenomena that has attracted significant interest is tip-sample dissipation, which was initially investigated by Cleveland and coworkers [Appl. Phys. Lett. 72, 2613–2615 (1998)]. In this paper we expand on that work by developing a method to map the total conservative and non-conservative forces simultaneously in space and as a function of relative tip-sample velocity. This is accomplished through Fourier analysis performed on the response of a torsional harmonic cantilever (THC) probe, previously developed by Sahin and coworkers [Nature Nanotechnology 2, 507–514 (2007)]. The effect of a select group of AFM parameters (cantilever resonant frequency, force constant, quality factor, amplitude set point and excitation amplitude) is simulated in a feasible range of experimental conditions, which maximizes the spatial and velocity range of the oscillating tip, such that useful maps of the total force as a function of tip velocity and position can be acquired. We analyze the observed trends and propose an approach to acquire analytical models of the local tip-sample dissipative and conservative forces.

Determining Necessary Parameters for Nanoinjector Electrodes During Attraction

This paper outlines the adaptation of a mathematical computer model used to simulate the motion of DNA particles in order to determine the best geometry and setup for a prototype cell injection system. The model predicts DNA motion due to electrophoresis near micromachined electrodes. Ten key electrode parameters are identified to test for significance, and three key test measurements are identified to help compare the various setups. A simple design of experiment is used to organize and analyze the data collected from forty-one simulations of the DNA motion within the electric field. Based on the simulations of attracting DNA to the lance for injection, it is found that a compact ring electrode placed underneath an insulated lance will yield the optimal results. Two additional areas for research are recommended.