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We present an electronic skin with proximity sensing capabilities. Through a simple and cheap fabrication process, we integrate carbon nanotube forests, which serve as the sensing element, into soft, flexible, and transparent artificial skin. Numerical simulations demonstrate the operational principle of the electronic skin proximity sensors. Experimental characterization reveals excellent repeatability and performance of the electronic skin proximity sensors, which are unaffected by the applied strain. Mounting the electronic skin on experimenter’s finger further demonstrates its high performance, variability, and potential to interface with humans. Thus, the cheap and simple fabrication process of this electronic skin, together with its straightforward operation, high reliability, and excellent performance under large deformations and different working conditions, set the stage for the development of a new generation of high-end flexible sensory electronic skin, which is attractive in a wide range of engineering fields, such as autonomous soft robotics, biomedicine, and the Internet of Things.

We demonstrate self-sensing tungsten disulfide nanotube (WS

Early and reliable detection of an infectious viral disease is critical to accurately monitor outbreaks and to provide individuals and health care professionals the opportunity to treat patients at the early stages of a disease. The accuracy of such information is essential to define appropriate actions to protect the population and to reduce the likelihood of a possible pandemic. Here, we show the fabrication of freestanding laser-induced graphene (FLIG) flakes that are highly sensitive sensors for high-fidelity viral detection. As a case study, we show the detection of SARS-CoV-2 spike proteins. FLIG flakes are nonembedded porous graphene foams ca. 30 μm thick that are generated using laser irradiation of polyimide and can be fabricated in seconds at a low cost. Larger pieces of FLIG were cut forming a cantilever, used as suspended resonators, and characterized for their electromechanics behavior. Thermomechanical analysis showed FLIG stiffness comparable to other porous materials such as boron nitride foam, and electrostatic excitation showed amplification of the vibrations at frequencies in the range of several kilo-hertz. We developed a protocol for aqueous biological sensing by characterizing the wetting dynamic response of the sensor in buffer solution and in water, and devices functionalized with COVID-19 antibodies specifically detected SARS-CoV-2 spike protein binding, while not detecting other viruses such as MS2. The FLIG sensors showed a clear mass-dependent frequency response shift of ∼1 Hz/pg, and low nanomolar concentrations could be detected. Ultimately, the sensors demonstrated an outstanding limit of detection of 2.63 pg, which is equivalent to as few as ∼5000 SARS-CoV-2 viruses. Thus, the FLIG platform technology can be utilized to develop portable and highly accurate sensors, including biological applications where the fast and reliable protein or infectious particle detection is critical.

Three-dimensional graphene foams (GFs) benefit from a large surface area and unique physical properties. We present here the first-ever miniaturized GF-based resonators. We developed a simple yet reliable fabrication process, in which GFs are synthesized and assembled on a cavity to form suspended GF devices. We electrostatically excited these devices and analyzed their resonance and ring-down responses. We observed significant energy dissipation, as the quality factor of the devices was in the order of several tens. Additionally, we investigated the influence of temperature on the operation of the devices and found that high temperatures mechanically soften the resonators but also considerably enhance energy dissipation. Finally, our devices demonstrated a mode-coupling of a resonance mode and a mode having twice its frequency. Thus, this work paves the way toward the development of novel GF resonators that could be integrated into future devices, such as GF-based nano-electromechanical sensors, electrical circuits, and oscillators.

We experimentally determine the elastic properties of 2D HfS2 and HfSe2 – two emerging nano-materials whose moderate energy bandgap and dielectric oxidized layer make them highly attractive for functional electronic and optoelectronic systems. We found that the average Young's moduli of HfS2 and HfSe2 nano-drumheads are relatively low (45.3 ± 3.7 GPa for a 12.2 nm thick HfS2 and 39.3 ± 8.9 GPa for a 13.4 nm thick HfSe2) and depend on the thickness of the nano-drumhead (increasing with thickness for HfS2 and decreasing for HfSe2). Moreover, both materials demonstrate outstanding stretchability (fracture strength and maximal strain of 5.7 ± 0.4 GPa and 12.2–14.3%, respectively, for HfS2; fracture strength and maximal strain of 4.5 ± 1.4 GPa and 14.0–20.9%, respectively, for HfSe2), which far exceeds the stretchability of other 2D materials and of polymers that are commonly used in flexible electronic applications. Finally, we describe the controlled oxidation of HfSe2 using a relatively simple laser treatment, which increased the Young's moduli of the thin oxidized layers to 182.6 ± 54.3 GPa. The extraordinary elastic properties of HfS2 and HfSe2, together with their excellent electrical and optoelectrical properties, make these 2D materials highly attractive for use in strain engineering and in various stretchable electronic and optoelectronic applications, such as wearable devices.

Graphene foam (GF)—a three-dimensional network of hollow graphene branches—is a highly attractive material for diverse applications. However, to date, the heat dissipation characteristics of GFs have not been characterized. To fill this gap, we synthesized GF devices, subjected them to high temperatures, and investigated their thermal behavior by using infrared microthermography. We find that while the convective area of GF devices is comparable to that of bulk materials (such as metals), the coefficient of convection of these devices is several orders of magnitude higher than that of metals. In addition, the GF devices showed a reproducible thermal behavior, which we attribute to negligible temperature-induced morphological changes (as confirmed by Raman analysis). Taken together, our findings suggest GF as a promising candidate material for advanced cooling applications where efficient heat dissipation is needed, e.g., in electrical circuits.

Thermal microelectromechanical system (MEMS) devices have gained immensely in popularity due to their good performances, relatively simple fabrication process, and to the availability of modeling tools. In this paper, the modeling results of several models were compared and the ability of each to reliably assess the performances of V-shaped thermal MEMS devices was investigated. The results of several models, in which the governing equations of motion were directly solved, were compared to those obtained from nonlinear large-deflection 3-D finite element analysis that was verified experimentally. The models were modified by including the temperature-dependent properties of the material of the device. In addition, a numerical iterative force control solution scheme was developed and used to predict the performances of V-shaped devices. Important parameters of V-shaped devices, such as apex deflection, stiffness, and output force, were evaluated in terms of the applied temperature and device geometry. In addition, the feasibility of capacitive sensing was demonstrated and high signal-to-noise ratio was calculated. Finally, the influence of microfabrication tolerances and internal stress on the performances of the devices were studied. Therefore, this paper will help future researchers and designers to assess the reliability of models of thermal MEMS devices and better evaluate device performance.

We experimentally determine the elastic properties of 2D HfS

Two dimensional (2D) materials are characterized by an in-plane strong covalent bond and out-of-plane weak Van der Waals bond between the constituent atoms. Graphene, a single layer of carbon atoms arranged in the honeycomb structure, is the most prominent example of such materials with distinctive linear dispersion leading to its unique optical and electronic properties. However, the lack of an energy bandgap limits its applicability in electronic and optoelectronic devices [1] , [2] . Atomically thin transition metal di-chalcogenides (TMD) are direct bandgap materials [4] . This fact opens new possibilities for optoelectronic applications, especially when combined with their excellent mechanical flexibility and high carrier mobility, widely tunable bandgap, valley polarization, and strong light-matter interaction [3] – [5] .

The effective dissipation of heat from electronic devices is essential to enable their long-term operation and their further miniaturization. Graphene foams (GF) and carbon nanotube (CNT) forests are promising materials for thermal applications, including heat dissipation, due to their excellent thermal conduction and low thermal interface resistance. Here, we study the heat transfer characteristics of these two materials under forced convection. We applied controlled airflow to heated samples of GF and CNT forests while recording their temperature using infrared micro-thermography. Then, we analyzed the samples using finite-element simulations in conjunction with a genetic optimization algorithm, and we extracted their heat fluxes in both the horizontal and vertical directions. We found that boundary layers have a profound impact on the heat transfer characteristics of our samples, as they reduce the heat transfer in the horizontal direction. The heat transfer in the vertical direction, on the other hand, is dominated by the material conduction and is much higher than the horizontal heat transfer. Accordingly, we uncover the fundamental thermal behavior of GF and CNT forests, paving the way toward their successful integration into thermal applications, including cooling devices.

Capacitive sensors are key components in a wide range of sensing applications, such as gas detectors and safety systems. While the mainstream silicon sensors demonstrated good performances, vertically aligned carbon nanotubes (VA-CNTs) outperform them and, therefore, are an attractive candidate material for capacitive applications owing to their extremely high surface area. Specifically, their top (crust) layer is characterized by a porous and dense morphology that further enhances the capacitive area and, consequently, induces an electrostatic fringe field and an enhancement of the capacitance. In this paper, we study how the porosity of VA-CNTs determines their electrostatic behavior. We observed that the porous surface of the crust layer generates a significant enhancement of the capacitance comparing to parallel plate capacitors. The rough surface of the crust layer results in amplification of the VA-CNT effective capacitor area, which further increases with the electrostatic gap. As-grown VA-CNTs with lower porosity demonstrate higher capacitance; however, densified samples and samples reinforced with conductive nano-particles did not show an enhancement of the capacitance, due to a significant change in their CNT formation. Thus, this paper emphasizes the influence of the morphological structure of VA-CNTs on their capacitance and enriches the material library that can be used for capacitive sensing.

Due to their excellent physical properties and compatibility with micro-fabrication processes, vertically aligned carbon nanotubes (VA-CNTs) have been successfully integrated in various nano/micro-electromechanical system (NEMS/MEMS) devices, composites, and electronic circuits. Here, we investigate the behavior of VA-CNTs under electrostatic tension. Scanning electron microscopy revealed that electrostatic tension reorganizes the individual CNTs and increases their alignment, thereby increasing their stiffness, and resulting in a negative Poisson's ratio (NPR). High NPR values were obtained in the top portion of the VA-CNTs (the location of the greatest morphological change), while the other portions (a less significant morphological change) demonstrated smaller NPR values. Therefore, the electrostatic pressure induces an irreversible morphological change in the VA-CNTs, which, in turn, modifies their properties. This behavior makes VA-CNTs an attractive material for a wide range of micro- and nano-scale devices, wherein tunable mechanical properties and a versatile motion transformation are required.

While boron-nitride foam (BNF) has shown remarkable properties, such as large surface area, wide bandgap, and high chemical and thermal stability, its realization as a resonator is a critical step toward its implementation into sensors, ultraviolet optical devices, and high-power systems. Here, we demonstrate BNF composite resonators. We first characterized the response of the resonators under mechanical loading, followed by their resonance excitation under the influence of Kelvin polarization force. In parallel, we built a model that clarifies the trends in the operation of our resonators. We found that the Kelvin polarization force induces a stiffening of the resonators, which allows resonance frequency tuning. Also, the Kelvin polarization force enables the excitation of BNF composites from a distance, while eliminating the need for high-precision fabrication and electrical wiring. Therefore, we uncover the fundamental physical behavior of BNF and pave the path toward its integration into advanced functional devices.

Carbon nanotube (CNT) forests have been successfully integrated into wide range of thermal applications due to their high thermal conductance, mechanical compliance, and compatibility with nano-fabrication processes. However, their successful large-scale integration into functional systems requires thorough understanding of their physical behavior. In this work, we studied how the morphological structure of CNT forests is modified due to the application of thermal loads and its interplay with their thermal and mechanical properties. Our investigation has shown that the thermal load enhances the alignment of initially bent CNTs. The CNTs alignment, in turn, influences the thermal transition temperatures and the mechanical stiffness of CNT forests. Therefore, this work sheds light on the coupling between thermal loads and the physics of CNT forest and, thus, will facilitate their successful large-scale use.

We study for the first time the resonant torsional behaviors of inorganic nanotubes, specifically tungsten disulfide (WS2) and boron nitride (BN) nanotubes, and compare them to that of carbon nanotubes. We have found WS2 nanotubes to have the highest quality factor (Q) and torsional resonance frequency, followed by BN nanotubes and carbon nanotubes. Dynamic and static torsional spring constants of the various nanotubes were found to be different, especially in the case of WS2, possibly due to a velocity-dependent intershell friction. These results indicate that inorganic nanotubes are promising building blocks for high-Q nanoelectromechanical systems (NEMS).

The continuous miniaturization of electronic devices substantially increases their power density, and consequently, requires effective cooling of these components. Vertically aligned carbon nanotubes (VA-CNTs) constitute one of the most promising materials for use as a high-end heat dissipation element due to their high thermal conductivity and large surface area. However, the lack of a clear understanding of the heat transfer mechanisms of VA-CNTs has so far impeded their large-scale use as cooling elements. Our infrared micro-thermography analysis revealed that the heat dissipation of VA-CNTs is determined mainly by their height, such that the heat dissipation behavior of tall samples was dominated by convection from the carbon nanotube (CNT) sidewalls. The mechanism of heat transfer in short VA-CNTs, in contrast, was determined by their morphology. Short VA-CNTs with highly organized CNT formations or with low thermal conductance exhibited convective heat dissipation similar to that of tall VA-CNTs, while other short VA-CNTs exhibited heat transfer dominated by conduction along the CNTs. This study provides important guidelines regarding the parameters that can be changed to optimize the performances of VA-CNTs in thermal applications. These applications include cooling elements in electronic devices, where convection is required, or thermal interface materials, where conduction is required.

Two-dimensional (2D) resonators are attractive for a wide range of applications, such as filters, sensors, and energy harvesters. In most cases, these resonators are excited electrostatically, which dictates adjacent electrode geometry that limits the design flexibility. In the present work, we demonstrate the magnetic excitation of 2D resonators. Contrary to electrostatic excitation, the magnetic field can be applied from a distance, and as a result, this approach offers greater flexibility in the design of these devices. We characterized the magnetic excitation of devices of varying thicknesses (from 17 nm to 170 nm) and found that their resonance frequencies are in the mega-hertz range. In addition, we thoroughly studied dissipation mechanisms in our devices and found that magnetic excitation enhances energy loss due to resistive heating and magnetic losses. In addition, we found that the interactions between the resonators and air molecules are a dominant mechanism of dissipation, although it also promotes the cooling of the resonators through the transfer of heat to the air. Therefore, this work sets the groundwork for the development of magnetic 2D resonators, which will be integrated into flexible actuators, resonant sensors, etc.

Flexible temperature sensors are desired for a wide range of applications in engineering, biology, and medicine. In the present paper, we describe the development of novel flexible temperature sensors based on carbon nanotube (CNT) forest composites, and we demonstrate their ability to sense on-skin temperatures. The fabrication process of these sensors is simple and they demonstrate bio-compatibility, high performance, and a simple sensing scheme. When subjected to high temperatures, the CNTs are strained due to the thermal mismatch between the CNT forest and the matrix, which modifies their electrical resistance in a stable and reproducible temperature–resistance relationship. The sensors demonstrate sensitivities of ~ 0.1 Ω / ° C or higher, and show stable Young’s modulus of ~ 0.1 M P a for temperatures below 100 °C. These sensors, thus, pave the way toward a new generation of flexible, wearable, and bio-compatible temperature sensors, which can be used as flexible lab-on-a-chip devices or as a sensory artificial skin.

Bandgap tuning is an attractive property of two-dimensional semiconductors and monolayer MoS2, in particular. We report here the bandgap tuning of monolayer MoS2. This was achieved by growing monolayer MoS2 on optical fibers that were then subjected to torsion, such that pure shear was transferred to MoS2. The effect of shear was inferred from the observed photoluminescence spectrum, after which a blue shift of ∼ 10 meV / % emerged. Detailed analysis revealed that this shift is mainly due to the trion luminescence and less due to the excitons. This observation experimentally uncovers the behavior of MoS2 under a yet uncharted pure shear deformation, which may enable the development of devices, such as tunable electronic components and high-precision sensors.

Electrostatic loading is widely used for sensing and actuation in miniaturized electromechanical systems, yet classical designs involve geometric patterning of solid materials such as silicon and metal films. Conductive nanoporous materials for electrostatics may enable engineering of new functionalities arising from their compliance, internal surface forces, and high surface area. Toward this end, we investigate the response of vertically aligned carbon nanotube (CNT) “forests” to DC and AC electrostatic loads. First, the tensile strain-stress characteristics of patterned CNT forests was determined in a non-contact manner by cyclic DC electrostatic loading, revealing an increase of the effective Young's modulus with sequential load cycling. Next, we observed resonance can be excited by AC electrostatic loading, and that the resonance frequency increases with sequential sweeps of the AC load frequency. Both the DC and AC measurements indicate that residual stress that arises during CNT growth is relaxed upon electrostatic loading, causing stiffening of the structure. This study shows for the first time that CNT forests can function as bulk electrostatic elements, and their intrinsic low stiffness and quality factor may be suitable for development of wide bandwidth micro-resonators and adsorption-based sensors.

Graphene foam (GF)—a three-dimensional porous structure that comprises several graphene layers—has excellent physical properties and, consequently, exciting possible applications. In this work, we report the mechanical behavior of GFs that were grown using high-temperature chemical vapor deposition (CVD) and subjected to electrostatic tensile loads. We show that such loads reduce the mechanical stiffness of the GF (Young's modulus in the kilo-Pascal range) and release prestresses generated during growth. In addition, GF demonstrates electrostatic resonance. By characterizing the fundamental electromechanical behavior of GF, this Letter paves the way toward the development of novel GF-based devices, such as GF electrostatic resonant sensors, flexible capacitors, and micro- and nanoelectromechanical devices.

While surface capacitance is utilized widely for sensing and actuation in miniaturized systems, relatively little attention has been paid to its enhancement using engineered surface topography. We present how an engineered surface topography, specifically a cylindrical micropillar array, gives a significant enhancement of the surface capacitance compared to a flat surface of the same area. Arrays of silicon micropillars were fabricated and measured, and the results were validated using both an approximate analytical model and a numerical finite element model. At large gaps (hundreds of microns) between a flat probe and the top surface of the array, the capacitance is comparable to that of a flat surface, while at smaller gaps (

Gallium telluride (GaTe) is a layered material, which exhibits a direct bandgap (∼1.65 eV) regardless of its thickness and therefore holds great potential for integration as a core element in stretchable optomechanical and optoelectronic devices. Here, we characterize and demonstrate the elastic properties and electromechanical resonators of suspended thin GaTe nanodrums. We used atomic force microscopy to extract the Young's modulus of GaTe (average value ∼39 GPa) and to predict the resonance frequencies of suspended GaTe nanodrums of various geometries. Electromechanical resonators fabricated from suspended GaTe revealed fundamental resonance frequencies in the range of 10-25 MHz, which closely match predicted values. Therefore, this study paves the way for creating a new generation of GaTe based nanoelectromechanical devices with a direct bandgap vibrating element, which can serve as optomechanical sensors and actuators.

In this work we introduce a new class of fully compliant structures performing vibratory motion, yet characterized by non-zero averaged momentum, appearing due to time-dependency of the inertial parameters. The work is motivated by microelectromechancial systems (MEMS) applications, where an implementation of unidirectional, non-vibratory motion involving relative motion of parts is not desirable for reliability reasons. Instead of changing the mass, which is challenging on the microscale, the moment of inertia of the proof mass performing tilting vibrations is controlled in such a way that it is higher or lower depending on the sign of the velocity. This results in a non-zero angular momentum averaged over the period. The equations describing the dynamics of a generic structure with a time-varying inertia and in a rotating coordinate frame are derived by using a variational principle. Simple approximate expressions for the averaged momentum and steady tilting angle are obtained and validated numerically. Based on the model results for different operational scenarios, we demonstrate that these devices can be efficiently used in fully compliant actuators and vibratory angular rate sensors (microgyros) with a steady response in a sensing mode (“pseudospinning disk gyros”), as well as in a parametrically excited gyro. The structure can be viewed also as a first step toward the realization of dynamic materials (DM) which are substances with material properties that may change in space and time.

Experimental exploration of strained nanostructures, such as nanowires and bio-molecules, is essential for understanding their properties. However, the ability to apply and to quantify nanometer displacements is challenging. We present a novel MEMS nano-extensometer with integrated actuation and compliant de-amplification mechanism allowing the accurate characterization of stretched nanostructures. A feasibility study was followed by fabrication and characterization of the device. The de-amplified displacement was registered via optical microscopy and was processed using an improved digital image correlation algorithm to achieve nanometer measurement accuracy. Using our technique, nanoscale displacement can be determined by means of simple imaging tools. This was demonstrated by stretching suspended single wall carbon nanotubes.

Recent progress achieved in the fields of micro and nanoelectromechanical systems demands a reliable method for high resolution characterization of electrostatically actuated devices. This paper presents a study on optical detection of nanoscale displacements using digital image correlation (DIC) algorithms, commonly used in characterization of in-plane displacements. Optical images of an electrostatically actuated micro electromechanical systems (MEMS) device were processed using a modified drift corrected DIC (DC-DIC) algorithm and the results were analyzed. Using the DC-DIC, the resolution was enhanced significantly and displacement measurements with nanoscale accuracy were captured using standard optics and processing tools. The present study provides a simple and reliable technique for optical characterization of rigid body nanoscale displacements of micro devices.

In this work we report on the novel architecture and operational principle of a tilting actuator with integrated motion transformer and amplifier fabricated using single structural layer of silicon on insulator (SOI) wafer and demonstrate the functionality of the device both theoretically and experimentally. The device incorporates an integrated compliant motion amplifier realized as an eccentric elastic torsion link that transforms small out-of-plane motion of the parallel-plate electrostatic transducer into large amplitude angular motion of the tilting element. A feasibility study and evaluation of design parameters were performed using a lumped model of the device and coupled three-dimensional simulation. Experimental and model results indicate that this generic architecture, combining simple fabrication process with robustness of SOI-based devices, is efficient for static and resonant operation of various tilting microdevices.

In the present study, we tested the feasibility of actuation of microplates by fringing electrostatic fields, i.e., field lines between plates and the sidewalls supporting them. Unlike the common close-gap actuation mechanism usually used in these kinds of devices, we present an alternative operational principle based on an electrostatic fringe field for the actuation of micro electromechanical (MEMS) plates, which is especially beneficial for open air environment operation. In order to validate the actuation principle, a circular MEMS plate was considered and an analytical model was built. The electrostatic force applied to the plate was extracted from a solution of a steady boundary value problem of a cylinder and was validated numerically using finite element simulation. This was followed by a solution of the plate governing equation of motion using an expansion theorem. Devices of two different geometries were fabricated and operated. Actuation of the plates by means of the fringing field was demonstrated experimentally. The proposed architecture and actuation principle is advantageous and overcomes many of the difficulties encountered in microplates electrostatically actuated by a close-gap electrode. Due to the absence of a small gap, the device is not prone to pull-in instability and stiction and is not subjected to squeeze-film damping. Moreover, since the actuation is separated from the front side of the device, open air contaminations, such as humidity or dust, cannot cause operational failure. In addition, the device is especially beneficial for mass sensing in an open environment, as well as flow senors where a flush-mounted smooth surface is important.

Vertically aligned carbon nanotubes (VA-CNTs) hold the potential to play an instrumental role in a wide variety of applications in micro- and nano-devices and composites. However, their successful large-scale implementation in engineering systems requires a thorough understanding of their material properties, including their thermal behavior, which was the focus of the current study. Thus, the thermal expansion of as-grown VA-CNT microstructures was investigated while increasing the temperature from room temperature to 800 °C and then cooling it down. First thermal transition was observed at 191±68 °C during heating, and an additional thermal transition was observed at 523±138 °C during heating and at similar temperatures during cooling. Each thermal transition was characterized by a significant change in the coefficient of thermal expansion (CTE), which can be related to a morphological change in the VA-CNT microstructures. Measurements of the CTEs in the lateral directions revealed differences in the la...

Following the recent progress in integrating single-wall carbon nanotubes (SWCNTs) into silicon-based micro-electromechanical systems (MEMS), new modeling tools are needed to predict their behavior under different loads, including thermal, electrical and mechanical. In the present study, the mechanical behavior of SWCNTs under thermoelectrical loading is analyzed using a large deflection geometrically nonlinear string model. The effect of the resistive heating was found to have a substantial influence on the SWCNTs behavior, including significant enhancement of the strain (up to the millistrains range) and buckling due to the thermal expansion. The effect of local buckling sites was also studied and was found to enhance the local strain. The theoretical and numerical results obtained in the present study demonstrate the importance of resistive heating in the analysis of SWCNTs and provide an additional insight into the unique mechanics of suspended SWCNTs.

In this work we present, for the first time, an on-chip sub-nanometer displacement sensing scheme. The sensing is achieved using integrated single wall carbon nanotubes (SWCNTs) as the sensing element. A novel fabrication process was used to suspend SWCNTs in a micro electromechanical (MEMS) device and integrate them onto special MEMS stretching devices, which was used to apply controlled nanoscale stretching to the SWCNTs while monitoring their electrical resistivity. Experimental results show that the SWCNTs resistance significantly changed under sub-nanometer stretching, thus demonstrating the realization of an ultra-sensitive MEMS displacement sensor.

We present a single wall carbon nanotube (SWCNT) based high frequency resonator fabricated using a novel process suitable for mass fabrication. The integration of the electrostatically actuated SWCNT into the silicon structure was achieved by a specially tailored fabrication process which is characterized by simplicity and compatibility with commonly used micro-machining processes. The fabrication process enables the control of the SWCNT positioning and its length and results in a taut and clean suspended SWCNT. Electro-mechanical testing of these devices demonstrates a resonance frequency of 13.4 MHz. Resonators with various resonance frequencies can be readily fabricated by varying the SWCNT length.

We report on a novel architecture and operational principle of a large angle kinematically excited tilting micro actuator. The device transforms and amplifies small linear out-of-plane motion of a parallel-plate electrostatic transducer into a tilting motion of a plate. The device characterized by robust single layer architecture was fabricated using a silicon on insulator (SOI) wafer and common deep reactive ion etching (DRIE) based fabrication process. Experimental and model results collectively illustrate the feasibility and efficiency of the suggested actuation approach. The optical tilting angle of 37.5° was experimentally registered under relatively low actuation voltage of 100 V.

In this work we present an experimental study of the electromechanical behavior of suspended, taut, single walled carbon nanotubes (SWCNTs). A novel top-down fabrication process was developed in order to integrate the suspended SWCNTs into silicon MEMS structures fabricated using conventional micro-machining techniques. The resonant response of suspended SWCNTs under a time-varying electric field was analyzed and resonant frequencies in MHz range were registered. In addition, the electromechanical characterization of metallic-like, small band-gap-like and semiconductor-like SWCNTs under steady electric fields of varying strength was carried out and high sensitivity of SWCNTs to the gate voltage was observed. The experimental results demonstrate feasibility of the adopted fabrication framework and provide an additional insight into the complex behavior of taut, suspended SWCNT.

We report on the novel architecture and operational principle of a MEMS accelerometer with enhanced sensitivity achieved through incorporating of an integrated mechanical compliant motion transformer and amplifier. The amplification mechanism is realized as an eccentric elastic torsion link that transforms small out-of-plane motion of the proof mass into large amplitude angular motion of a tilting element whose deflection are sensed optically to extract acceleration. The device was fabricated using silicon on insulator (SOI) wafer and is characterized by a robust single layer architecture and simple fabrication process. The functionality of the device is demonstrated and good agreement between theoretical and experimental results is observed.

We present novel operational principle of a tilting MEMS device based on parametric excitation and linear to angular motion transformation. The device is fabricated using a single layer of silicon on insulator (SOI) wafer and combines simple fabrication process with several beneficial features including large tilting angles, wide bandwidth, low sensitivity to deviation in geometrical and operational parameters and low actuation voltage. A theoretical feasibility and performance study was carried out using a lumped model of the device and verified by a coupled three-dimensional simulation. Parametric excitation of the tilting motion was demonstrated experimentally using and external piezoelectric transducer and tilting angles of 39° were registered. The suggested operational approach could be efficiently implemented in many MEMS based applications incorporating tilting elements including micromirrors, bio medical devices and inertial sensors.

Understanding of the electrostatic properties of carbon nanotube (CNT) forests is essential to enable their integration in microelectronic and micromechanical devices. In this study, we sought to understand how the hierarchical geometry and morphology of CNT forests determines their capacitance. First, we find that at small gaps, solid micropillars have greater capacitance, yet at larger gaps the capacitance of the CNT forests is greater. The surface area of the CNT forest accessible to the electrostatic field was extracted by analysis of the measured capacitance, and, by relating the capacitance to the average density of CNTs in the forest, we find that the penetration depth of the electrostatic field is on the order of several microns. Therefore, CNT forests can behave as a miniature Faraday cage. The unique electrostatic properties of CNT forests could therefore enable their use as long-range proximity sensors and as shielding elements for miniature electronic devices.

We apply an interpolation-based edge-tracking algorithm to measure nanoscale displacements of microdevices, and further enhance its ability to reject noisy signals using averaging of multiple image frames. We present a simulation of a moving edge, and use this simulation to explore the performance of the algorithm as related to the image acquisition and process parameters. Then, we present the application of this technique to two experiments. First, we demonstrate optical measurement of the motion of a compliant mechanism, and smoothly detect lateral step motion change as small as 30.8 nm s−1. Second, we measure the anisotropic nanoscale expansion of a liquid crystal network micropillar, which occurs slowly over several minutes. This efficient algorithm can smoothly track motions as small as a few per cent of a pixel, which is equivalent to tens of nanometers using images from a video camera attached to a conventional optical microscope. Therefore, this technique can be widely applied to characterization of nanoscale motions using conventional optics, without requiring special features on the device to enable imaging.

The influence of perforation on the electrostatic force for thick micro-electromechanical (MEMS) structures is analyzed theoretically and experimentally. A three-dimensional numerical model is provided in order to evaluate the influence of the fringe capacitive field on the electrostatic force. Several configurations of perforated MEMS structures were characterized under ambient air conditions and experimental results demonstrate good consistency with the model prediction. Moreover, a comparative study on the effect of perforation on damping (quality factor) was performed. A quality factor was experimentally determined by analyzing frequency response under electrostatic excitation and time response under pulse loading, and was compared to a few analytical models, which demonstrate reasonable agreement with the measured results. Our study demonstrates that perforation has a significant effect on the quality factor, while its contribution of the electrostatic fringe capacitive field ranges between additional few to few tens of per cents.

The integration of suspended carbon nanotubes into micron-scale silicon-based devices offers many exciting advantages in the realm of nano-scale sensing and micro- and nano-electromechanical systems (MEMS and NEMS). To realize such devices, simple fabrication schemes are needed. Here we present a new method to integrate carbon nanotubes into silicon-based devices by applying conventional micro-fabrication methods combined with a guided chemical vapor deposition growth of single-wall carbon nanotubes. The described procedure yields clean, long, taut and well-positioned tubes in electrical contact to conducting electrodes. The positioning, alignment and tautness of the tubes are all controlled by the structural and chemical features of the micro-fabricated substrate. As the approach described consists of common micro-fabrication and chemical vapor deposition growth procedures, it offers a viable route toward MEMS–NEMS integration and commercial utilization of carbon nanotubes as nano-electromechanical transducers.