Inspired by the auditory systems of small animals, such as spiders, the tachinid fly, Ormia ochracea, and mosquitoes, a novel low-noise, flow-sensing capacitive MEMS microphone capable of sensing acoustic particle velocity is introduced. Unlike conventional microphones that have a diaphragm for sensing sound pressure, this design consists of a thin, porous, movable structure that is intended to be driven by viscous forces as a result of the sound-induced flow. This viscous force then rotates the movable structure around a middle central hinge and creates a change in capacitance caused by a relative motion between neighboring beams. The whole structure is made of one layer of silicon using a silicon-on-insulator (SOI) wafer using photolithography technology with a device layer thickness of 5 μm. The movable part has dimensions of 0.7 mm × 1.2 mm and is placed above a cavity inside the bulk silicon that facilitates the flow of sound particles. This microphone responds to flow (a vector) rather than pressure (a scalar). Ultimately, experimental results demonstrate a sensitivity of approximately 5 mV/Pa, a noise floor between 10−4 and 10−5 Pa/Hz, and directivity ratios reaching up to 77 at 2000 Hz, underscoring its potential for high-performance acoustic applications.

Treatment with Adriamycin (ADR) is one of the major causes of chemotherapy-induced cardiotoxicity and therefore is the principal limiting factor in the effectiveness of chemotherapy for cancer patients. Apigenin (API) has been shown to play a cardioprotective role. The present study examined the effect of API on ADR-induced cardiotoxicity in mice. Sixty male Kunming mice were randomly divided into 4 groups: a control group, ADR model group, low-dose API treatment group (125 mg·kg-1), and high-dose API treatment group (250 mg·kg-1). Blood samples were taken to evaluate a spectrum of myocardial enzymes. Cardiomyocyte apoptosis was measured using a TUNEL assay, and cardiomyocyte autophagy was observed using electron microscopy. Moreover, apoptosis-related proteins, such as Bax and Bcl-2, autophagy-related proteins, including Beclin1 and LC3B, and PI3K/AKT/mTOR pathway-related proteins were examined with western blot. Our results demonstrate that ADR caused an increase in the serum levels of cardiac injury markers and enhanced cardiomyocyte apoptosis and autophagy. API administration prevented the effects associated with ADR-induced cardiotoxicity in mice and inhibited ADR-induced apoptosis and autophagy. API also promoted PI3K/AKT/mTOR pathway activity in ADR-treated mice. In conclusion, API may have a protective effect against ADR-induced cardiotoxicity by inhibiting apoptosis and autophagy via activation of the PI3K/AKT/mTOR pathway.

Microfabrication is a critical area to many branches of science and engineering. However, to many students accustomed to seeing transistors as things that come in a lab kit, it is an obscure subtopic of their discipline. Beginning in 2009, the authors undertook a broad multidisciplinary approach to bring microfabrication into all aspects of the Binghamton University science and engineering curriculum. This program was coupled with a comprehensive assessment activity to evaluate the program's effectiveness and continuously improve it year by year. This paper reports the details of the implementation process, the techniques that were found to bring a hands-on experience to large classes, and the lessons learned from the assessments of this program to make this topic a mainstream part of engineering and science education.

A silicon microelectromechanical systems microphone is described that detects sound pressure gradients. The diaphragm consists of a stiffened plate that rotates around a central axis in response to sound pressure gradients. The motion of the diaphragm is converted into an electronic signal through the use of interdigitated comb fins that enable capacitive sensing. Measured results show that the microphone achieves a substantially lower low-frequency sound pressure-referred noise floor than can be achieved using existing dual miniature microphone systems. Measured directivity patterns are shown to be very close to what is expected for sound pressure gradient receivers over a broad range of frequencies.

We present a study of the dynamic behavior of a MEMS device constituted of an imperfect clamped-clamped microbeam subjected to electrostatic and electrodynamic actuation. Our objective is to develop a theoretical analysis, which is able to describe and predict all the main relevant aspects of the experimental response. Extensive experimental investigation is conducted, where the main imperfections coming from microfabrication are detected and the nonlinear dynamics are explored at increasing values of electrodynamic excitation, in a neighborhood of the first symmetric resonance. The nonlinear behavior is highlighted, which includes ranges of multistability, where the non-resonant and the resonant branch coexist, and intervals where superharmonic resonances are clearly visible. Numerical simulations are performed. Initially, two single mode reduced-order models are considered. One is generated via the Galerkin technique, and the other one via the combined use of the Ritz method and the Padé approximation. Both of them are able to provide a satisfactory agreement with the experimental data. This occurs not only at low values of electrodynamic excitation, but also at higher ones. Their computational efficiency is discussed in detail, since this is an essential aspect for systematic local and global simulations. Finally, the theoretical analysis is further improved and a two-degree-of-freedom reduced-order model is developed, which is capable also to capture the measured second symmetric superharmonic resonance. Despite the apparent simplicity, it is shown that all the proposed reduced-order models are able to describe the experimental complex nonlinear dynamics of the device accurately and properly, which validates the proposed theoretical approach.

We present a study of the dynamic behavior of a microelectromechanical systems (MEMS) device consisting of an imperfect clamped-clamped microbeam subjected to electrostatic and electrodynamic actuation. Our objective is to develop a theoretical analysis, which is able to describe and predict all the main relevant aspects of the experimental response. Extensive experimental investigation is conducted, where the main imperfections coming from microfabrication are detected, the first four experimental natural frequencies are identified and the nonlinear dynamics are explored at increasing values of electrodynamic excitation, in a neighborhood of the first symmetric resonance. Several backward and forward frequency sweeps are acquired. The nonlinear behavior is highlighted, which includes ranges of multistability, where the nonresonant and the resonant branch coexist, and intervals where superharmonic resonances are clearly visible. Numerical simulations are performed. Initially, two single mode reduced-order models are considered. One is generated via the Galerkin technique, and the other one via the combined use of the Ritz method and the Pade approximation. Both of them are able to provide a satisfactory agreement with the experimental data. This occurs not only at low values of electrodynamic excitation, but also at higher ones. Their computational efficiency is discussed in detail, since this is an essential aspect for systematic local and global simulations. Finally, the theoretical analysis is further improved and a two-degree-of-freedom reduced-order model is developed, which is also capable of capturing the measured second symmetric superharmonic resonance. Despite the apparent simplicity, it is shown that all the proposed reduced-order models are able to describe the experimental complex nonlinear dynamics of the device accurately and properly, which validates the proposed theoretical approach.

A MEMS differential microphone is described in which the diaphragm design is inspired by the mechanics of directional hearing in the fly Ormia ochracea. The 1 mm by 3 mm diaphragm is designed to rotate about a central pivot in response to sound pressure gradients. The diaphragm is designed to have its dominant resonance mode within the audible frequency range and to have as little viscous damping as possible (to minimize the effects of thermal noise). The motion of the diaphragm is detected using an optical sensing scheme that includes a semiconductor laser (VCSEL), photodetectors, a mirror, and a diffraction grating. To minimize the adverse effects of the light damping on the response, an active feedback system is implemented to achieve active Q control. This uses the output of the optical detection scheme to drive the diaphragm through a capacitive actuator. The microphone and optoelectronics are packaged into an assembly that can be incorporated into a mock behind-the-ear hearing aid. The microphone is shown to achieve a noise floor that is approximately 17 dBA lower than what can be achieved using a pair of existing low noise hearing aid microphones to create a directional hearing aid.

A Conceptual Framework for the Development of a Course in Nano/Micro-Scale Systems Engineering Cetin Cetinkaya1 ∗, Ian I. Suni2, Silvana Andreescu3, Mandy B. Esch4, Weili Cui5, David J. Jones6, Stephen Jones5, Gregory S. Chojecki7, James D. Stephens1, and Armin S. Vahdat1 1Department of Mechanical and Aeronautical Engineering, 2Materials Technology Center, Southern Illinois University, Carbondale, IL 62901, USA 3Department of Chemistry and Biomolecular Science, Clarkson University, Potsdam, NY 13699, USA 4Department of Biomedical Engineering, Cornell University, Ithaca, NY 14853, USA 5Department of Mechanical Engineering, State University of New York at Binghamton, Binghamton, NY 13902, USA 6Global Foundries, Malta, NY 12020, USA 7Department of Chemical and Biomolecular Engineering, Clarkson University, Potsdam, NY 13699, USA

Microfabrication is a critical area to many branches of science and engineering. Beginning in 2009, we undertook a broad multidisciplinary approach to bring microfabrication into all aspects of the science and engineering curriculum. This program was coupled with a comprehensive assessment activity to evaluate the program's effectiveness and continuously improve it year to year. In this paper, we report on the details of our implementation process, the techniques we have found to bring a hands-on experience to large classes and the lessons learned from our attempts to make this topic a mainstream part of engineering and science education.

In this study we present a theoretical and experimental investigation of a microelectromechanical system (MEMS). The device is constituted of a clamped-clamped polysilicon microbeam electrostatically and electrodynamically actuated. The microbeam has a slightly curled up configuration, which is an imperfection commonly encountered as a consequence of the microfabrication process. Using a laser Doppler vibrometer, many experimental frequency sweeps are conducted in a neighborhood of the first symmetric natural frequency. To simulate the dynamics, we derive a single-mode reduced-order model. Extensive numerical investigations are performed, based on frequency response diagrams and behavior charts. The overall scenario of the response is explored, when both the frequency and the electrodynamic voltage are varying. This analysis is able to provide a very good matching with the experiments. Nevertheless, the theoretical predictions are not completely fulfilled in some aspects. In particular, the range of existence of each attractor is smaller in practice than in the simulations. This is because the theoretical curves represent the ideal limit case where disturbances are absent, which never occurs in experiments and practice. To overcome this drawback and extend the results to the practical case where disturbances exist, we develop a dynamical integrity analysis. After introducing dynamical integrity concepts, we perform integrity profiles and integrity charts. They are able to describe if each attractor is robust enough to tolerate the disturbances. They detect the parameter range where each branch can be reliably observed in practice and where, instead, becomes vulnerable, i.e., depending on the expected disturbances, they provide valuable information to operate the device in safe conditions according to the desired outcome.

A highly innovative miniature silicon comb sense differential microphone diaphragm is described that is highly stable when subjected to various bias voltages [1]. The bio-inspired microphone diaphragm consists of a 1mm by 2mm stiffener-reinforced plate fabricated out of phosphorous doped polysilicon that is supported on a central hinge [2, 3, and 4]. Interdigitated comb fingers are formed around the perimeter at the ends of the diaphragm by reactive ion etching the polysilicon to create the gaps between the two sets of comb fingers. It is demonstrated with a fabricated prototype device that this design avoids many key limitations of capacitive microphones through use of a unique comb-sensing design and approach. It provides the means for design and construction of highly innovative capacitive microphones with enhanced sensitivity that can be readily and cost-effectively produced through silicon microfabrication. Potential applications include manufacturing of next-generation hearing aids, security devices, portable digital devices, cell phones and teleconferencing equipment.

A silicon micromachined biomimetic optical microphone has been recently demonstrated to have directional response and low noise [J. Acoust. Soc. Am. 125(4), 2013–2026 (2009)]. In this microphone, the motion of one end of the pivoting rectangular diaphragm is detected using an integrated optical interferometer and each end can be actuated using separate electrostatic actuators. This configuration enables one to selectively enhance either the directional, anti-symmetric rocking mode or the omni-directional symmetrical second vibrational mode of the diaphragm in two separate active feedback loops. A circuit model with two electrical ports to actuate each side of the diaphragm, and two acoustic ports to drive each mode has been developed to illustrate the electronic method. The model includes the effect of the air medium and the backside cavity through mechanical impedances which are verified through measurements. With the two-sided active feedback scheme, the model predicts significant improvements in the directional response resulting in more than 10-dB improvement in the residual intensity index when the microphone is used for gradient measurement in an intensity probe.

The analysis and design of a MEMS directional microphone are described that incorporates electronic feedback to achieve active Q control. The microphone diaphragm consists of a 1 × 2-mm stiffened plate fabricated out of polycrystalline silicon that is supported on a central hinge. The sound pressure gradient incident on the diaphragm produces a rocking motion about the central hinge. Interdigitated comb fingers at each end of the diaphragm enable both capacitive sensing and electrostatic actuation. The diaphragm has been designed to have its dominant resonant mode have a frequency of approximately 1 kHz. By minimizing sources of passive damping, the thermal noise of the microphone has been shown to be lower than the noise floor of existing two-microphone systems used in directional hearing aids [Miles et al., J. Acoust. Soc. Am. 125 (2009)]. However, this low-passive damping also results in an undesirable resonance within the audible frequency range. To minimize the adverse effects of this resonance, a simple analog electronic feedback system is designed that can result in acceptable performance in both the frequency and time domains. [Work funded by NIH Grant R01 DC009429.]

Microfabrication is a critical area to many branches of science and engineering. In this work-in-progress paper, we describe our plan to introduce microfabrication technology in a comprehensive, cross-curricular way through lectures, demonstrations and experiments from freshman through junior classes across four disciplines (Electrical and Mechanical Engineering, Chemistry, and Physics). Immediately following, in the senior year, will be an opportunity for students in these disciplines to take a multidisciplinary microfabrication capstone course that will serve as a complete introduction to clean room theory and practice. This approach will fundamentally show microfabrication as being based on many disciplines and vital to most modern technologies. Assessment will be done for each level of the project, and assessment results will be used to continuously improve the course over time and gauge the success of attracting students into this area.

An in situ electron microscopy study is presented of adhesion interactions between single-walled carbon nanotubes (SWNTs) by mechanically peeling thin free-standing SWNT bundles using in situ nanomanipulation techniques inside a high-resolution scanning electron microscope. The in situ measurements clearly reveal the process of delaminating one SWNT bundle from its originally bound SWNT bundle in a controlled-displacement manner and capture the deformation curvature of the delaminated SWNT bundle during the peeling process. A theoretical model based on nonlinear elastica theory is employed to interpret the measured deformation curvatures of the SWNTs and to quantitatively evaluate the peeling force and the adhesion strength between bundled SWNTs. The estimated adhesion energy per unit length for each pair of neighboring tubes in the peeling interface based on our peeling experiments agrees reasonably well with the theoretical value. This in situ peeling technique provides a potential new method for separating bundled SWNTs without compromising their material properties. The combined peeling experiments and modeling presented in this paper will be very useful to the study of the adhesion interactions between SWNTs and their nonlinear mechanical behaviors in the large-displacement regime.

We present an investigation of the nonlinear dynamics of clamped-clamped micromachined arches when actuated by a dc electrostatic load superimposed on an ac harmonic load. The Galerkin method is used to discretize the distributed-parameter model of a shallow arch to obtain a reduced-order model. The static response of the arch due to a dc load actuation is simulated, and the results are validated by comparing them to experimental data. The dynamic response of the arch to a combined dc load and ac harmonic load is studied when excited near its fundamental natural frequency, twice its fundamental natural frequency, and near other higher harmonic modes. The results show a variety of interesting nonlinear phenomena, such as hysteresis, softening behavior, dynamic snap-through, and dynamic pull-in. The results are also shown demonstrating the potential to use microelectromechanical systems (MEMS) arches as bandpass filters and low-powered switches. An experimental work is conducted to test arches realized of curved polysilicon microbeams when excited by dc and ac loads. Experimental data are shown for the softening behavior and the dynamic pull-in of the curved microbeams.

The effect of the shape and distribution of perforations in parallel plate capacitive MEMS devices on squeeze-film damping is presented. The squeeze film effect is the most important damping effect on the dynamic behavior of most MEMS devices that employ capacitive sensing and actuation, which typically employ narrow air gaps between planar moving surfaces [1, 2]. The stationary plate of a capacitive device is often perforated to reduce the damping and sensor noise and improve the frequency response. The formula for determining the total viscous damping in the gap contains a coefficient Cp that is associated with the geometry and distribution of the holes on the stationary plate. In this study, the coefficient Cp is determined using the finite element method using ANSYS by analogy with heat conduction in a solid with internal heat generation. Round, elliptical, rectangular, and oval holes that are distributed either aligned or offset are analyzed and compared. It is shown that the surface fraction occupied by the perforations is not the only factor that determines Cp. Both the shape and distribution strongly affect the damping coefficient [3, 4]. By using elongated perforations that are properly distributed, the squeeze film damping could be minimized with the minimum amount of perforation. The analysis performed in this work is quite general being applicable to a very large spectrum of frequencies and to various fluids in capacitive sensors. These results can facilitate the design of mechanical structures that utilize capacitive sensing and actuation, such as accelerometers, optical switches, micro-torsion mirrors, resonators, microphones, etc.

A miniature differential microphone is described having a low-noise floor. The sensitivity of a differential microphone suffers as the distance between the two pressure sensing locations decreases, resulting in an increase in the input sound pressure-referred noise floor. In the microphone described here, both the diaphragm thermal noise and the electronic noise are minimized by a combination of novel diaphragm design and the use of low-noise optical sensing that has been integrated into the microphone package. The differential microphone diaphragm measures 1 x 2 mm(2) and is fabricated out of polycrystalline silicon. The diaphragm design is based on the coupled directionally sensitive ears of the fly Ormia ochracea. The sound pressure input-referred noise floor of this miniature differential microphone has been measured to be less than 36 dBA.