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In this paper, we discuss using the Casimir force in conjunction with a MEMS parametric amplifier to construct a quantum displacement amplifier. Such a mechanical amplifier converts DC displacements into much larger AC oscillations via the quantum gain of the system which, in some cases, can be a factor of a million or more. This would allow one to build chip scale metrology systems with zeptometer positional resolution. This approach leverages quantum fluctuations to build a device with a sensitivity that can’t be obtained with classical systems.

Optical systems typically use galvanometers (galvos) and scanners. Galvos move, quasi-statically, from one static position to another. Scanners move in an oscillatory fashion, typically at the device resonant frequency. MEMS devices, which have many advantages and are often used in optical systems, are typically high Q devices. Moving from one position to another for a galvo or one amplitude to another for scanners, can take many periods to settle following the ring down. During these transitions, the optical system is inactive. Here, we show how precisely timed pulses can be used (in an open loop manner) to begin or end scanner motion without ring up/ring down time. The size of pulse required is found to depend on the Q of the device, and relationships are derived. The pulse can also be separated into multiple pulse spaced one period apart if pulses of the necessary size are not possible due to constraints of the physical device. For finite Q scanners, the amplitude decreases after the initial pulse due to damping. This can be eliminated by applying an excitation at the frequency of the scanner. The necessary amplitude for this excitation is derived. Finally, by combining this open loop control algorithm with an open loop control algorithm for galvo motion the device can seamlessly move between scanner and galvo functioning. These control algorithms are demonstrated using computer simulations, analytical models and a commercially available MEMS mirror (Mirrorcle Technologies, A8L2.2). [2020-0238]

In this article, we present a nanoelectromechanical system (NEMS) designed to detect changes in the Casimir energy. The Casimir effect is a result of the appearance of quantum fluctuations in an electromagnetic vacuum. Previous experiments have used nano- or microscale parallel plate capacitors to detect the Casimir force by measuring the small attractive force these fluctuations exert between the two surfaces. In this new set of experiments, we aim to directly detect the shifts in the Casimir energy in a vacuum due to the presence of the metallic parallel plates, one of which is a superconductor. A change in the Casimir energy of this configuration is predicted to shift the superconducting transition temperature (Tc) because of the interaction between it and the superconducting condensation energy. In our experiment, we take a superconducting film, carefully measure its transition temperature, bring a conducting plate close to the film, create a Casimir cavity, and then measure the transition temperature again. The expected shifts are smaller than the normal shifts one sees in cycling superconducting films to cryogenic temperatures, so using a NEMS resonator in situ is the only practical way to obtain accurate, reproducible data. Using a thin Pb film and opposing Au surface, we observe no shift in Tc >12 µK down to a minimum spacing of ~70 nm at zero applied magnetic field., Measuring quantum fluctuations with NEMS A nano-electromechanical system (NEMS) allows for the direct measurement of Casimir energy. The Casimir effect relates to the fluctuation of electromagnetic waves between two plates in a vacuum. Previous studies used plate capacitors that function by detecting small Casimir forces exerted on the plates by the electromagnetic fluctuations. Now, a team from the United States and Switzerland led by David Bishop, of Boston University, Massachusetts, and Vladimir Aksyuk of the National institute of Standards and Technology, have developed a technique in which a thin lead superconductor film is placed parallel to a gold surface. This allows direct measurements as the plate and film are brought close together and the actual Casimir energy in the cavity changes. The team measured the Casimir energy via its effect on the superconductor’s “transition temperature”, finding changes no more than 12 micro-Kelvin. The team says their paper “opens a novel experimental window” that future studies should exploit.

Inductive circuits and devices are ubiquitous and important design elements in many applications, such as magnetic drives, galvanometers, magnetic scanners, applying direct current (DC) magnetic fields to systems, radio frequency coils in nuclear magnetic resonance (NMR) systems, and a vast array of other applications. They are widely used to generate both DC and alternating current (AC) magnetic fields. Many of these applications require a rapid step and settling time, turning the DC or AC magnetic field on and off quickly. The inductive response normally makes this a challenging thing to do. In this article, we discuss open loop control algorithms for achieving rapid step and settling times in four general categories of applications: DC and AC systems where the system is either under- or over-damped. Each of these four categories requires a different algorithm, which we describe here. We show the operation of these drive methods using Simulink and Simscape modeling tools, analytical solutions to the underlying differential equations, and experimental results using an inductive magnetic coil and a Hall sensor. Finally, we demonstrate the application of these techniques to significantly reduce ringing in a standard NMR circuit. We intend this article to be practical, with useful, easy-to-apply algorithms and helpful tuning tricks.

The Casimir force, a quantum mechanical effect, has been observed in several microelectromechanical system (MEMS) platforms. Due to its extreme sensitivity to the separation of two objects, the Casimir force has been proposed as an excellent avenue for quantum metrology. Practical application, however, is challenging due to attractive forces leading to stiction and device failure, called Casimir pull-in. In this work, we design and simulate a Casimir-driven metrology platform, where a time-delay-based parametric amplification technique is developed to achieve a steady-state and avoid pull-in. We apply the design to the detection of weak, low-frequency, gradient magnetic fields similar to those emanating from ionic currents in the heart and brain. Simulation parameters are selected from recent experimental platforms developed for Casimir metrology and magnetic gradiometry, both on MEMS platforms. While a MEMS offers many advantages to such an application, the detected signal must typically be at the resonant frequency of the device, with diminished sensitivity in the low frequency regime of biomagnetic fields. Using a Casimir-driven parametric amplifier, we report a 10,000-fold improvement in the best-case resolution of MEMS single-point gradiometers, with a maximum sensitivity of 6 Hz/(pT/cm) at 1 Hz. Further development of the proposed design has the potential to revolutionize metrology and may specifically enable the unshielded monitoring of biomagnetic fields in ambient conditions.

Optical systems typically use galvanometers (aka galvos) and scanners. Galvos move optical elements such as mirrors, quasi-statically, from one static position to another, and an important figure of merit is their step-settle relaxation time. Scanners move in an oscillatory fashion, typically at the device resonant frequency. MEMS devices, which have many advantages and are often used in such optical systems, are typically high Q devices. Moving from one position to another for a galvo or one frequency/amplitude to another for scanners, can take many periods to settle following the ring down. During these transitions, the optical system is inactive and the time is not being efficiently used. In this article we show how a novel class of open loop control algorithms can be used to rapidly change position, frequency and amplitude, typically in well under the period of the device. We show how the MEMS designer can excite, with complete, high-speed control, a vibrational mode of the system. We call this modal engineering, the ability to control the modes of the system in a practical, fast way. This control of the modes is accomplished with open loop control algorithms.

Systematic investigations of the effects of mechano-electric coupling (MEC) on cellular cardiac electrophysiology lack experimental systems suitable to subject tissues to in-vivo like strain patterns while simultaneously reporting changes in electrical activation. Here, we describe a self-contained motor-less device (mechano-active multielectrode-array, MaMEA) that permits the assessment of impulse conduction along bioengineered strands of cardiac tissue in response to dynamic strain cycles. The device is based on polydimethylsiloxane (PDMS) cell culture substrates patterned with dielectric actuators (DEAs) and compliant gold ion-implanted extracellular electrodes. The DEAs induce uniaxial stretch and compression in defined regions of the PDMS substrate at selectable amplitudes and with rates up to 18 s−1. Conduction along cardiomyocyte strands was found to depend linearly on static strain according to cable theory while, unexpectedly, being completely independent on strain rates. Parallel operation of multiple MaMEAs provides for systematic high-throughput investigations of MEC during spatially patterned mechanical perturbations mimicking in-vivo conditions., While strain is known to affect cardiac electrophysiology, experimental systems to interrogate the effect of rapid strain cycles on cardiac tissue are lacking. Here the authors introduce a multielectrode array that can induce rapid dynamic strain cycles on cardiomyocyte strands and see effects of strain amplitude but not strain rate on impulse conduction.

Microelectromechanical systems (MEMS) provide engineers with a rich palette of technical solutions to a wide range of actuation and sensing challenges. MEMS devices are low cost, easily integrated with sense and drive electronics, are robust, and can be designed to respond to electrical, mechanical, or chemical stimuli. Because they are mechanical, MEMS devices suffer from being relatively slow in comparison with purely electronic devices. However, it has been shown that by using feedforward drives developed using controls theory approaches, it is possible to significantly improve the step and settle time of MEMS actuators. This paper uses this technique to demonstrate the use of pulse width modulation to linearly drive MEMS. Furthermore, it demonstrates an overdrive method capable of improving the step and settle time of a commercial MEMS device by a factor of 1500. The approach is general and can be used for a wide range of devices and actuation methods, such as electrostatic, electromagnetic, and thermal actuation. This provides engineers a simple method to design high ${Q}$ MEMS devices with sub-millisecond response times, opening the phase space for more micromechanical solutions. [2017-0261]

Using a microelectromechanical systems (MEMS)-based Fab-on-a-Chip, we quench-condense lead thin-films. Suppressing the formation of lead islands makes it possible to grow a homogeneous and continuous film as thin as 2 nm, without the use of an adhesion layer. Thermal cycling from 3 K to as low as 10 K reveals irreversible annealing of the thin-film characteristic of a metastable state. The transition to the stable state is smooth and is completed by cycling the temperature above,similar to 42 K, where a distinctive resistance minimum is observed. This resistive minimum is accompanied by an unexpected peak in the superconducting transition temperature. After further thermal cycling, the standard metallic/superconductive behavior is established. The MEMS-based approach yields a platform for systematic studies of quench-condensed thinfilm materials, making an intriguing parameter space of mesoscopic physics experimentally accessible.

Insects are a constant source of inspiration for roboticists. Their compliant bodies allow them to squeeze through small openings and be highly resilient to impacts. However, making subgram autonomous soft robots untethered and capable of responding intelligently to the environment is a long-standing challenge. One obstacle is the low power density of soft actuators, leading to small robots unable to carry their sense and control electronics and a power supply. Dielectric elastomer actuators (DEAs), a class of electrostatic electroactive polymers, allow for kilohertz operation with high power density but require typically several kilovolts to reach full strain. The mass of kilovolt supplies has limited DEA robot speed and performance. In this work, we report low-voltage stacked DEAs (LVSDEAs) with an operating voltage below 450 volts and used them to propel an insect-sized (40 millimeters long) soft untethered and autonomous legged robot. The DEAnsect body, with three LVSDEAs to drive its three legs, weighs 190 milligrams and can carry a 950-milligram payload (five times its body weight). The unloaded DEAnsect moves at 30 millimeters/second and is very robust by virtue of its compliance. The sub-500-volt operation voltage enabled us to develop 780-milligram drive electronics, including optical sensors, a microcontroller, and a battery, for two channels to output 450 volts with frequencies up to 1 kilohertz. By integrating this flexible printed circuit board with the DEAnsect, we developed a subgram robot capable of autonomous navigation, independently following printed paths. This work paves the way for new generations of resilient soft and fast untethered robots.

There is a world-wide push to create the next generation all-optical transmission and switching technologies for exascale data centers. In this paper we focus on the switching fabrics. Many different types of 2D architectures are being explored including MEMS/waveguides and semiconductor optical amplifiers. However, these tend to suffer from high, path dependent losses and crosstalk issues. The technologies with the best optical properties demonstrated to date in large fabrics (>100 ports) are 3D MEMS beam steering approaches. These have low average insertion losses, and equally important, a narrow loss distribution. However, 3D MEMS fabrics are generally dismissed from serious consideration for this application because of their slow switching speeds (~few milliseconds) and costs ($100/port). In this paper we show how novel feedforward open loop controls can solve both problems by improving switching speeds by two orders of magnitude and costs by one order of magnitude. With these improvements in hand, we believe 3D MEMS fabrics can become the technology of choice for data centers.

The Casimir Effect is a physical manifestation of quantum fluctuations of the electromagnetic vacuum. When two metal plates are placed close together, typically much less than a micron, the long wavelength modes between them are frozen out, giving rise to a net attractive force between the plates, scaling as d−4 (or d−3 for a spherical-planar geometry) even when they are not electrically charged. In this paper, we observe the Casimir Effect in ambient conditions using a modified capacitive micro-electromechanical system (MEMS) sensor. Using a feedback-assisted pick-and-place assembly process, we are able to attach various microstructures onto the post-release MEMS, converting it from an inertial force sensor to a direct force measurement platform with pN (piconewton) resolution. With this system we are able to directly measure the Casimir force between a silver-coated microsphere and gold-coated silicon plate. This device is a step towards leveraging the Casimir Effect for cheap, sensitive, room temperature quantum metrology. The Casimir effect is a quantum fluctuation force that exists between conducting surfaces separated by hundreds of nanometers, and the effect holds promise for application as a sensing tool in conjunction with an inexpensive micro-electromechanical system (MEMS) device. A team headed by Alexander Stange in the Bishop group at Boston University, United States, observed the Casimir effect under ambient conditions using a modified off-the-shelf MEMS sensor. The authors were able to integrate a Casimir cavity with the MEMS device by attaching various microstructures onto the MEMS sensor, converting it into a customized force measurement platform. The team believes that the Casimir effect has considerable potential as a practical, controllable sensing tool and that it could be used for such purposes as temperature sensing, AC voltage measurements, and low-impedance current measurements.

Integrated circuits with nanomaterial components can revolutionize technology, but only if they can be economically fabricated in large numbers.

Capacitive comb actuators are widely used as MEMS motors due to their long range of linear motion, low power consumption, and ease of fabrication. Here, we present data from a thin comb capacitive actuator where fringe fields contribute significantly to the device performance. We characterize the observed levitation effect and discuss two methods to control the out-of-plane forces: 1) by means of alternating the comb polarity; and 2) by using an additional electrode below the comb. Considering two alternative designs, it is shown how the levitation force can be mitigated. One design decreases the out-of-plane motion by a factor of two, but also reduces the lateral range. An alternative design proved successful in decreasing out-of-plane motion by 75%, while enhancing the in-plane displacement of the linear comb actuator by over 35%.

This article is a review of the dissipation processes in nanoelectromechanical systems (NEMS). As NEMS technology becomes more and more prevalent in research and engineering applications, it is of great importance to understand the dissipative mechanisms that in part define the dynamic response of such devices. The purpose of this work is to understand, sort, and categorize dominant dissipation sources and to determine their significance with respect to physics processes and engineering considerations.

We report the observation of nonlinear dissipation in diamond nanomechanical resonators measured by an ultrasensitive heterodyne down-mixing piezoresistive detection technique. The combination of a hybrid structure as well as symmetry breaking clamps enables sensitive piezoresistive detection of multiple orthogonal modes in a diamond resonator over a wide frequency and temperature range. Using this detection method, we observe the transition from purely linear dissipation at room temperature to strongly nonlinear dissipation at cryogenic temperatures. At high drive powers and below liquid nitrogen temperatures, the resonant structure dynamics follows the Pol-Duffing equation of motion. Instead of using the broadening of the full width at half-maximum, we propose a nonlinear dissipation backbone curve as a method to characterize the strength of nonlinear dissipation in devices with a nonlinear spring constant.

We present a microelectromechanical system (MEMS) based method for the resist-free patterning of nanostructures. Using a focused ion beam to customize larger MEMS machines, we fabricate apertures with features less than 50 nm in diameter on plates that can be moved with nanometer precision over an area greater than 20 × 20 μm(2). Depositing thermally evaporated gold atoms though the apertures while moving the plate results in the deposition of nanoscale metal patterns. Adding a shutter positioned micrometers above the aperture enables high speed control of not only where but also when atoms are deposited. With this shutter, different-sized apertures can be opened and closed selectively for nanostructure fabrication with features ranging from nano- to micrometers in scale. The ability to evaporate materials with high precision, and thereby fabricate circuits and structures in situ, enables new kinds of experiments based on the interactions of a small number of atoms and eventually even single atoms.

We present the use of a micromirror to dynamically improve an optical wireless communiciations link. The signal-to-noise ratio (SNR) is improved by directing the output of a 675 nm laser diode modulated at 10 MHz toward a receiver and by varying the divergence of the output beam using a varifocal, tip-tilt-piston micromirror. The SNR has a dynamic range of 30 dB for a diffuse source, all by optimizing the overall shape and direction of the mirror.

We present a microelectromechanical systems (MEMS) tunable metamaterial, Fabry-Perot interferometer with a widely tunable mid-infrared response. An array of subwavelength holes in a gold film is suspended above a gold reflector, forming an interferometer cavity whose length can be modulated over a range of 1.7 to 21.67 mu m using MEMS electrostatic actuation. Reflectance spectra exhibit the convolution of extraordinary optical transmission through the holes and Fabry-Perot resonances with free spectral ranges from 2900 to 230.7 cm(-1). Measuring the free spectral range enables us to perform in situ interferometric calibration of the cavity length. We present a simple analytical model that describes the experimental and simulated results. This device shows promise as a surface-enhanced sensing substrate with a tunable spectral response.

Micro/Nano Electro Mechanical Systems (MEMS/NEMS) provide the engineer with a powerful set of solutions to a wide variety of technical challenges. However, because they are mechanical systems, response times can be a limitation. In some situations, advanced engineered drive techniques can improve response times by as much as a thousand, significantly opening up the application space for MEMS/NEMS solutions., 37 pages, 20 figures

In this paper we discuss the development of a MEMS-based solid state atom source that can provide controllable atom deposition ranging over eight orders of magnitude, from ten atoms per square micron up to hundreds of atomic layers, on a target ∼1 mm away. Using a micron-scale silicon plate as a thermal evaporation source we demonstrate the deposition of indium, silver, gold, copper, iron, aluminum, lead and tin. Because of their small sizes and rapid thermal response times, pulse width modulation techniques are a powerful way to control the atomic flux. Pulsing the source with precise voltages and timing provides control in terms of when and how many atoms get deposited. By arranging many of these devices into an array, one has a multi-material, programmable solid state evaporation source. These micro atom sources are a complementary technology that can enhance the capability of a variety of nano-fabrication techniques.

MEMS micromirrors have proven to be very important optical devices with applications ranging from steerable mirrors for switches and cross-connects to spatial light modulators for correcting optical distortions. Usually beam steering and focusing are done with different MEMS devices and tilt angles in excess of 10 degrees are seldom obtained. Here we describe a single MEMS device that combines tip/tilt, piston mode and varifocal capability into a single, low cost device with very large tilt angles. Our device consists of a 400 micron diameter mirror driven with thermal bimorphs. We have demonstrated deflection angles of ± 40 degrees along both axes, a tunable focal length which varies between −0.48 mm to + 20.5 mm and a piston mode range of 300 microns - four separately controllable degrees of freedom in a single device. Potential applications range from smart lighting to optical switches and devices for telecom systems.

MEMS mirrors are currently used in many applications to steer beams of light. An area of continued research is developing mirrors with varifocal capability that allows the beam to be shaped and focused. In this work, we study the varifocal capability of a 380 mu m diameter, thermally actuated MEMS mirror with a +/- 40 degrees tip-tilt angle and a radius of curvature between -0.48 mm to 20.5 mm. Light is coupled to the mirror via a single mode optical fiber, similar to an indoor optical wireless communication architecture. The performance of the mirror is characterized with respect to (1) the profile of the reflected beam as the mirror deforms and (2) the mirror's impact when integrated into an optical communication system. We found that the mirror can focus light to a beam with a 0.18 degrees half-angle divergence. Additionally, the ability to change the shape of fiberized light from a wide to narrow beam provides an unmatched level of dynamic control and significantly improves the bit error rate in an optical communication system. (C) 2017 Optical Society of America.

The ability to actively shift the primary resonance of a 2D scanning micromirror allows the user to set the scanning direction, set the scanning frequency, and lift otherwise degenerate modes in a symmetrically designed system. In most cases, resonant scanning micromirrors require frequency stability in order to perform imaging and projection functions properly. This paper suggests a method to tune the tip and tilt resonant frequencies in real time while actively suppressing or allowing degeneracy of the two modes in a symmetric electrothermal micromirror. We show resonant frequency tuning with a range of degeneracy separation of 470 Hz or by approximately +/- 15% and controllable coupling. (C)2017 Optical Society of America

Nano-electromechanical systems (NEMS) are extraordinary in their ability to transduce minute mechanical signals into an electrical response. The methods of inducing and detecting mechanical, electrical, or biological signals using diamond NEMS structures are discussed in this chapter. Diamond, with its unique mechanical, thermal, and chemical properties, is a fascinating material. It often outperforms conventional NEMS materials, such as silicon. Advances in thin-film growth and fabrication methods now make it possible to manufacture ever more sensitive devices with far-reaching implications in both applied and fundamental research. This chapter illustrates the inner workings of diamond NEMS devices. Furthermore, opportunities and technological challenges in the field of diamond NEMS are discussed.

In this paper, we discuss a design for a MEMS parametric amplifier modulated by the Casimir force. We present the theory for such a device and show that it allows for the implementation of a very sensitive voltage measuring technique, where the amplitude of a high quality factor resonator includes a tenth power dependency on an applied DC voltage. This approach opens up a new and powerful measuring modality, applicable to other measurement types., Comment: 18 pages, 4 figures

International audience; We report direct measurements of average vibration energy in a high frequency flexural resonance mode achieved via an-harmonic elastic coupling to a fundamental vibration mode of a nanomechanical resonator. The second order coupling effect produces a frequency shift of the read-out mode as a function of the mean square of the excitation amplitude of the high order mode. We measure frequency shifts at the lowest driving amplitudes, down to the noise floor of the experimental setup. With implementation of existing ultra-sensitive amplifiers, the reported technique will enable direct measurements of quantized energy transitions in low-thermal occupation number nanomechanical resonators.

We report kelvin to millikelvin-temperature measurements of dissipation and frequency shift in megahertz-range resonators fabricated from ultra-nanocrystalline diamond. Frequency shift $\delta f/f_0$ and dissipation $Q^{-1}$ demonstrate temperature dependence in the millikelvin range similar to that predicted by the glass model of tunneling two level systems. The logarithmic temperature dependence of $\delta f/ f_0$ is in good agreement with such models, which include phonon relaxation and phonon resonant absorption. Dissipation shows a weak power law, $Q^{-1}\propto T^{{1/3}}$, followed by saturation at low temperature. A comparison of both the scaled frequency shift and dissipation in equivalent micromechanical structures made of single-crystal silicon and gallium arsenide indicates universality in the dynamical response., Comment: 5 pages, two figures, one table, two-column format. Related papers can be found at http://nano.bu.edu/

We demonstrate a silicon-based high frequency nanomechanical device capable of switching controllably between two states at room temperature. The device uses a nanomechanical resonator with two distinct states in the hysteretic nonlinear regime. In contrast to prior work, we demonstrate room temperature electrostatic actuation and sensing of the switching device with 100% fidelity by phase modulating the drive signal. This phase-modulated device can be used as a low-power high-speed mechanical switch integrated on-chip with silicon circuitry., Comment: 10 pages, 3 figures. Related papers can be found at http://nano.bu.edu/

Extensive measurements have been made with pions, electrons and muons on four production wedges of the Compact Muon Solenoid (CMS) hadron barrel (HB) calorimeter in the H2 beam line at CERN with particle momenta varying from 20 to 300 GeV/c. Data were taken both with and without a prototype electromagnetic lead tungstate crystal calorimeter (EB) in front of the hadron calorimeter. The time structure of the events was measured with the full chain of preproduction front-end electronics running at 34 MHz. Moving-wire radioactive source data were also collected for all scintillator layers in the HB. These measurements set the absolute calibration of the HB prior to first pp collisions to approximately 4%.

We report measurements of synchronization in two nanomechanical beam oscillators coupled by a mechanical element. We charted multiple regions of frequency entrainment or synchronization by their corresponding Arnold's tongue diagrams as the oscillator was driven at subharmonic and rational commensurate frequencies. Demonstration of multiple synchronized regions could be fundamentally important to neurocomputing with mechanical oscillator networks and nanomechanical signal processing for microwave communication.

We report frequency and dissipation scaling laws for doubly-clamped diamond resonators. The device lengths range from 10 microns to 19 microns corresponding to frequency and quality-factor ranges of 17 MHz to 66 MHz and 600 to 2400 respectively. We find that the resonance frequency scales as 1/L^2 confirming the validity of the thin-beam approximation. The dominant dissipation comes from two sources; for the shorter beams, clamping loss is the dominant dissipation mechanism; while for the longer beams, surface losses provide a significant source of dissipation. We compare and contrast these mechanisms with other dissipation mechanisms to describe the data., 5 pages, two-column format. Related papers available at http://nano.bu.edu/

The low-energy dynamics of pions and magnons -- the Goldstone bosons of the strong interactions and of magnetism -- are analogous in many ways. The electroweak interactions of pions result from gauging an SU(2)_L x U(1)_Y symmetry which then breaks to the U(1)_{em} gauge symmetry of electromagnetism. The electromagnetic interactions of magnons arise from gauging not only U(1)_{em} but also the SU(2)_s spin rotational symmetry, with the electromagnetic fields E and B appearing as non-Abelian vector potentials. Pions couple to electromagnetism through a Goldstone-Wilczek current that represents the baryon number of Skyrmions and gives rise to the decay \pi^0 to \gamma \gamma. Similarly, magnons may couple to an analogue of the Goldstone-Wilczek current for baby-Skyrmions which induces a magnon-two-photon vertex. The corresponding analogue of photon-axion conversion is photon-magnon conversion in an external magnetic field. The baryon number violating decay of Skyrmions can be catalyzed by a magnetic monopole via the Callan-Rubakov effect. Similarly, baby-Skyrmion decay can be catalyzed by a charged wire. For more than two flavors, the Wess-Zumino-Witten term enters the low-energy pion theory with a quantized prefactor N_c -- the number of quark colors. The magnon analogue of this prefactor is the anyon statistics angle \theta which need not be quantized., Comment: 34 pages, no figures

Dissipation of energy in micro- and nano-electromechanical resonators governs their dynamical response and limits their potential use in device applications. Quantified by the quality factor Q, dissipation (Q− 1) usually occurs by energy loss mechanisms that are linear, appearing as a damping term proportional to the velocity. Mechanisms of linear dissipation in micro- and nano-mechanical resonators are well studied both theoretically and experimentally. Mechanisms of nonlinear dissipation of energy, however, are rarely studied, though their effects could be fundamentally important to the operation of numerous devices based on nonlinear resonators such as switches, signal processers, sensors, and energy harvesting systems. Here, we report experimental observation of nonlinear dissipation in diamond nanoelectromechanical resonators.

We report actuation and detection of gigahertz-range resonance frequencies in nano-crystalline diamond mechanical resonators. High order transverse vibration modes are measured in coupled-beam resonators exhibiting frequencies up to 1.441 GHz. The cantilever-array design of the resonators translates the gigahertz-range resonant motion of micron-long cantilever elements to the displacement of the central supporting structure. Use of nano-crystalline diamond further increases the frequency compared to single crystal silicon by a factor of three. High clamping losses usually associated with micron-sized straight beams are suppressed in the periodic geometry of our resonators, allowing for high quality factors exceeding 20,000 above 500 MHz., Comment: 5 pages, two figures, one table, two-column format. Related papers can be found at http://nano.bu.edu/

This paper presents the implementation of a system to capacitively self-sense the position of a comb drive based MEMS XY nanopositioner from a single common node. The nanopositioner was fabricated using the multi-users PolyMUMPs process, on which comb capacitors fringe fields are large and out of plane forces cause considerable deflection. An extensive analysis of the comb-drive capacitance including the levitation effects and its correlation to the measurements is presented. Each axis is independently measured using frequency division multiplexing (FDM) techniques. Taking advantage of the symmetry of the nanopositioner itself, the sensitivity is doubled while eliminating the intrinsic capacitance of the device. The electrical measured noise is 2.5 aF/Hz, for a sensing voltage Vsen = 3Vrms and fsen = 150 kHz, which is equivalent to 1.1 nm/Hz lateral displacement noise. This scheme can also be extended to N-degree of freedom nanopositioners. Fil: del Corro, Pablo Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Imboden, Matthias. École Polytechnique Fédérale de Lausanne; Suiza Fil: Perez, Diego Javier. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Boston University; Estados Unidos Fil: Bishop, David J.. Boston University; Estados Unidos Fil: Pastoriza, Hernan. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

This paper presents two capacitive comb drive designs for electrostatic actuation of MEMS with the aim to eliminate the levitation effect often observed in such systems. By placing a shield over the comb drive fingers, it is possible to balance the electric field and suppress vertical forces while maintaining the desired lateral motion. By optimizing the comb geometry, we demonstrate that our approach is able to reduce the levitation by an order of magnitude and unwanted coupling of motion from out-of-plane to in-plane by a factor of 7 compared with standard comb architectures fabricated using PolyMUMPs technology, without the need of alternating comb finger polarities or additional control electrodes. Levitation was reduced to 160 nm, for 3.6 μm lateral displacement at a driving voltage of 80 V. [2016-0156] Fil: del Corro, Pablo Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Bajas Temperaturas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina Fil: Imoden, Matthias. École Polytechnique Fédérale de Lausanne; Suiza Fil: Bishop, David J.. Boston University; Estados Unidos Fil: Pastoriza, Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Bajas Temperaturas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina

There is a world-wide push to create the next-generation all-optical transmission and switching technologies for exascale data centers. In this paper we focus on the switching fabrics. Many different types of 2D architectures are being explored including MEMS/waveguides and semiconductor optical amplifiers. However, these tend to suffer from high, path-dependent losses and crosstalk issues. The technologies with the best optical properties demonstrated to date in large fabrics (>100 ports) are 3D MEMS beam steering approaches. These have low average insertion losses and, equally important, a narrow loss distribution. However, 3D MEMS fabrics are generally dismissed from serious consideration for this application because of their slow switching speeds (similar to few milliseconds) and high costs ($100/port). In this paper we show how novel feedforward open loop controls can solve both problems by improving MEMS switching speeds by two orders of magnitude and costs by a factor of three. With these improvements in hand, we believe 3D MEMS fabrics can become the technology of choice for data centers. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Test assays capable of providing quantitative characterization of the contraction of cardiac and smooth muscle cells are of great need for drug development and screening. Several methodologies have been proposed for achieving measurement of cell contractile stress or force, however almost all rely on optical methods to detect contraction. Recently, we proposed a test assay method based on the cell-induced deformation of thin-film, elastomeric, capacitive sensors. The method uses an electrical (capacitive) read-out enabling facile up-scaling to a large number of devices working in parallel for high-throughput measurements. We present here a model for the prediction and optimization of sensor performance. Our model shows the following trends: a) a cell region ratio of approximately 0.75 of the culture well radius produces the largest change in capacitance for a given cell contractile stress, b) the change in capacitance generated by cell contraction increases as the Young’s modulus, sensing layer thickness and electrode thicknesses of the sensor decrease, following an inverse relationship. A prototype device is fabricated and characterized in cell culture conditions. Mean standard deviations as lows as 0.2 pF are achieved (

Software defined radios (SDR) in the microwave X and K bands offer the promise of low cost, programmable operation with real-time frequency agility. However, the real world in which such radios operate requires them to be able to detect nanowatt signals in the vicinity of 100 kW transmitters. This imposes the need for selective RF filters on the front end of the receiver to block the large, out of band RF signals so that the finite dynamic range of the SDR is not overwhelmed and the desired nanowatt signals can be detected and digitally processed. This is currently typically done with a number of narrow band filters that are switched in and out under program control. What is needed is a small, fast, wide tuning range, high Q, low loss filter that can continuously tune over large regions of the microwave spectrum. In this paper we show how extreme throw MEMS actuators can be used to build such filters operating up to 15 GHz and beyond. The key enabling attribute of our MEMS actuators is that they have large, controllable, out-of-plane actuation ranges of a millimeter or more. In a capacitance-post loaded cavity filter geometry, this gives sufficient precisely controllable motion to produce widely tunable devices in the 4-15 GHz regime., 12 pages 14 figures 2 tables

Here, we discuss a novel, mixed mode 3D XYZ scanner built within a single foundry process. The device has a large range of motion in X, Y, and Z ( $14.1~\mu \text{m}$ in X and Y and $97.9~\mu \text{m}$ in Z) and can also rotate about two axes (7.4°), making it a 5 degree of freedom scanner. Vertical actuation can be accomplished with both thermal actuators, which have a larger range of motion, and capacitive actuators, which are faster, responding fully up to 3.2 kHz. Although useful for many applications, including scanning probe microscopy, micrometer scale optical microscopy, and manipulation of biological objects, the device was designed to be a 3D scanner for spray-painting atoms upon a surface with nanoscale precision and resolution for nanofabrication. Demonstrating the ability to combine the device with other complicated MEMS systems, it is integrated with an XY scanner designed to serve as a shutter of atomic flux. The full system has 7 degrees of freedom and 12 actuation motors, and because it is built in a low cost commercial foundry with a robust and stable process, it is easy and inexpensive to fabricate multiple copies or integrate into other complicated systems, making a system of systems. [2018-0213]

A cell culture well with integrated mechanical and optical stimulation is presented. This is achieved by combining dielectric elastomer soft actuators, also known as artificial muscles, and a varifocal micro-electromechanical mirror that couples light from an optical fiber and focuses it onto the transparent cell substrate. The device enables unprecedented control ofin vitrocell cultures by allowing the experimenter to tune and synchronize mechanical and optical stimuli, thereby enabling new experimental assays in optogenetics, fluorescent microscopy, or laser stimulation that include dynamic mechanical strain as a controlled input parameter.

We present a mechanically active cell culture substrate that produces complex strain patterns and generates extremely high strain rates. The transparent miniaturized cell stretcher is compatible with live cell microscopy and provides a very compact and portable alternative to other systems. A cell monolayer is cultured on a dielectric elastomer actuator (DEA) made of a 30 μm thick silicone membrane sandwiched between stretchable electrodes. A potential difference of several kV’s is applied across the electrodes to generate electrostatic forces and induce mechanical deformation of the silicone membrane. The DEA cell stretcher we present here applies up to 38% tensile and 12% compressive strain, while allowing real-time live cell imaging. It reaches the set strain in well under 1 ms and generates strain rates as high as 870 s−1, or 87%/ms. With the unique capability to stretch and compress cells, our ultra-fast device can reproduce the rich mechanical environment experienced by cells in normal physiological conditions, as well as in extreme conditions such as blunt force trauma. This new tool will help solving lingering questions in the field of mechanobiology, including the strain-rate dependence of axonal injury and the role of mechanics in actin stress fiber kinetics.