The field of in situ nanomechanics is greatly benefiting from microelectromechanical systems (MEMS) technology and integrated microscale testing machines that can measure a wide range of mechanical properties at nanometer scales, while characterizing the damage or microstructure evolution in electron microscopes. This article focuses on the latest advances in MEMS-based nanomechanical testing techniques that go beyond stress and strain measurements under typical monotonic loadings. Specifically, recent advances in MEMS testing machines now enable probing key mechanical properties of nanomaterials related to fracture, fatigue, and wear. Tensile properties can be measured without instabilities or at high strain rates, and signature parameters such as activation volume can be obtained. Opportunities for environmental in situ nanomechanics enabled by MEMS technology are also discussed.

Strong magnetoelectric (ME) coupling realized in magnetic/ferroelectric multiferroic heterostructures provides great potential for different integrated multiferroic devices for sensing, power, RF, and µ-wave electronics. Here, we present the most recent progress on new integrated multiferroic devices including novel integrated magnetic tunable inductors with a wide operation frequency range; integrated nonreciprocal bandpass filter with dual H- and E-field tunability based on magnetostatics surface waves; dual H- and E-field tunable RF bandpass filters with nanomechanical ME resonators; RF nanomechanical ME resonators with pico-Tesla DC magnetic fields sensitivity; a new antenna miniaturization mechanism, acoustically actuated nanomechanical ME antennas, which successfully miniaturize the magnitude in 1-2 orders with the advantages of the high magnetic field sensitivity, highest antenna gain within all nanoscale antennas at the similar frequency, and ground plane immunity on the metallic surface and the human body.

Dynamic-mode cantilever sensors are used in many different applications but especially in materials research to study properties of novel (nano)materials. Decreasing sample sizes require an increase in sensitivity of the analysis tools. For cantilever-based methods that is achieved through a reduction in cantilever dimensions. However, the increase in sensitivity has to be balanced with the detectability as also for a small cantilever a reliable detection of its oscillatory state has to be ensured. A recently introduced co-resonant measurement principle for cantilever sensors addresses this challenge by coupling and eigenfrequency matching of a micro- and a nanocantilever. Here, the sensor concept is reviewed with focus on the application in materials research by the instructive example of an iron-filled carbon nanotube, giving insight into the features and benefits of the sensor concept and demonstrating the reliable derivation of magnetic sample properties.

Axisymmetric reverse extrusion experiments were conducted on annealed Cu rod specimens to form cup-shaped structures with sidewall thicknesses ranging from ∼400 µm down to ∼25 µm. Changes in Cu grain morphology, size, and texture were examined through scanning electron microscopy and electron backscatter diffraction (EBSD). Pole figure and orientation distribution function analysis of EBSD data showed the same texture components in the present small-scale metal forming experiments as those observed in macroscale sheet metal rolling. The plastic deformation became inhomogeneous as the characteristic dimension for extrusion decreased to ∼25 µm, such that the deformation process involved a small number of Cu grains. Extrusion force–punch displacement curves were measured as a function of extruded cup sidewall thickness and compared to outputs of a continuum plasticity finite element analysis in corresponding geometries. The present work illustrates materials characteristics in small-scale metal forming and suggests directions of future work for bringing improved correspondence between experimentation and modeling.

Here we present an investigation into the phase change mechanism and detection methods of the metal-insulator transition of vanadium dioxide (VO2). We are able to detect the onset of the phase transition, and track it to completion using both the mechanical and electrical response by depositing VO2/TiO2 layers onto microcantilever devices by pulsed laser deposition. The resonance frequency of v-shaped cantilevers was shown to increase by up to 41 % upon deposition of VO2 as detected by laser Doppler vibrometry. Such a large increase in resonance frequency is ascribed to high tensile stress imparted onto the cantilever during the deposition process. The insulator-metal transition manifested as a 5 % increase in the resonance frequency as a result of lattice compression, resulting in additional tensile stress in the more ordered metallic phase. Electrically, the transition was confirmed by over three orders magnitude decrease in resistance upon heating past the transition. The metal-insulator transition was measured with an accuracy of a few °C when comparing the two methods, however, the transition was much sharper in the mechanical response.

Graphene, a two-dimensional (2D) crystalline material exhibits unique electronic, optical, and mechanical properties which makes it a promising candidate for optomechanical and optoelectronic devices. The giant plasmonic activity of graphene sheets enables low-dimensional confinement of light and enhanced light–matter interaction leading to significant enhancement of optical forces which may give rise to large mechanical deformations on account of ultralow mass density and flexibility of graphene. The multilayer stack and heterostructures of 2D materials provide access to a spectrum of guided modes which can be used to tailor the optical forces and mechanical states of graphene sheets. Here, we study the optical forces arising from the coupling of guided modes in layered structures of graphene sheets. We obtain the mechanical deformation states corresponding to each guided mode and demonstrate that the optical forces can be adjusted by changing the interlayer spacing as well as the chemical potential of graphene layers. Our results can be used for various designs of graphene-based optomechanical devices.

Research of electrostrictive polymers has generated new opportunities for harvesting energy from the surrounding environment and converting it into usable electrical energy. Electroactive polymer (EAP) research is one of the new opportunities for harvesting energy from the natural environment and converting it into usable electrical energy. Piezoelectric ceramic based energy harvesting devices tend to be unsuitable for low-frequency mechanical excitations such as human movement. Organic polymers are typically softer and more flexible therefore translated electrical energy output is considerably higher under the same mechanical force. In addition, cantilever geometry is one of the most used structures in piezoelectric energy harvesters, especially for mechanical energy harvesting from vibrations. In order to further lower the resonance frequency of the cantilever microstructure, a proof mass can be attached to the free end of the cantilever. Mechanical analysis of an experimental bimorph structure was provided and led to key design rules for post-processing steps to control the performance of the energy harvester. In this work, methods of materials processing and the mechanical to electrical conversion of vibrational energy into usable energy were investigated. Materials such as polyvinyledenedifluoridetetra-fluoroethylene P(VDF-TrFE) copolymer films (1um thick or less) were evaluated and presented a large relative permittivity and greater piezoelectric β-phase without stretching. Further investigations will be used to identify suitable micro-electromechanical systems (MEMs) structures given specific types of low-frequency mechanical excitations (10-100Hz).

Stretchable electronics represent an emerging class of devices that can be compressed, twisted and conform to very complicated shapes. The mechanical and electrical compliances of the technology promise to open up applications for healthcare, energy and entertainment purposes. However, advancement in the field has been hindered by material related constraints. Moreover, the current microfabrication facilities are optimized for rigid substrates such as silicon, which have significant different properties compared to elastomers. In this paper, four categories of enabling technologies for stretchable electronics commercialization are critically reviewed, namely: the novel design of stretchable structures, use of non-conventional materials, state-of-art printing techniques and also the patterning of electrodes or metal interconnects via conventional manufacturing techniques.

A highly accurate multi-point pressure measurement system based on MEMS pressure sensors spliced into a fiber optic cable and suitable for downhole deployment in a CO2 sequestration well was designed, developed and tested in the laboratory. An interrogator system based on a pulsed laser excitation was shown to be capable of multiple (potentially 60+) point sensor measurements on a single fiber. The interrogator was interfaced with the GE PredixTM industrial internet to demonstrate a remote monitoring system. Sensor packages were fabricated and tested at high temperatures and pressures in supercritical CO2. Environmental and stress testing of the sensor components and package indicated areas in which the design of the package should be further improved.

We investigated the fabrication of convex diamond-like carbon (DLC) based microgears in room-temperature curing nanoimprint lithography (RTC-NIL) using the ladder-type hydrogen silsesquioxane (HSQ), as an application for the medical micro electro mechanical system (MEMS). The HSQ which is an inorganic polymer of sol-gel system turns into a gel when exposed to air and has the siloxane bond. Therefore, the HSQ was used as RT-imprinting material, and also used as an oxide mask material in electron cyclotron resonance (ECR) oxygen (O2) ion shower etching. We fabricated the polydimethylsiloxane (PDMS) mold with concave microgear patterns which has 40, 50 and 60 μm-tip diameter and 300 nm-depth. We carried out the RTC-NIL process using the PDMS mold under the following optimum conditions of 0.10 MPa-imprinting pressure and 1.0 min-imprinting time. We found that the residual layer of imprinted HSQ microgear patterns was removed with ECR trifluoromethane (CHF3) ion shower under the following conditions of 300 eV-ion energy and 2.0 min-etching time, and then microgears of the HSQ on the DLC film were etched with ECR O2 ion shower under the following conditions of 400 eV-ion energy and 10 min-etching time. As a result, the convex DLC based microgears which have 40, 50 and 60 μm-tip diameter and 400 nm-height were fabricated with high accuracy in the new fabrication process of RTC-NIL.

A water-developable sugar-based negative resist material was developed. This material enables the use of pure water in the development process of electron beam (EB) green lithography instead of conventionally used aqueous alkaline developers and organic solvents. The sugar-based negative resist material was developed by replacing the hydroxyl groups in alpha-linked disaccharides with EB-sensitive 2-methacryloyloxyethyl groups. The sugar-based negative resist material features highly efficient crosslinking and low film thickness shrinkage under EB irradiation. It is demonstrated to be applicable to green lithography with a 100– 500 nm line-and-space pattern and an EB exposure dose of 18 μC/cm2.

The paper presents the research results of influence of various parameters of magnetic field concentrator geometry on sensitivity of magnetically controlled MEMS switches. It is shown that magnetic sensitivity increases with the growth of the magnetic concentrator width and practically does not depend on its length. It is established that dependence of magnetic sensitivity on the overlap length of the ferromagnetic flexible contact-concentrator has a minimum corresponding to 2-3 lengths of the contact gap. Recommendations on sensitivity increase of magnetically controlled MEMS switches are provided.

We discuss the self-folding of patterned metallic sheets using both differential stress and surface forces. The advantageous characteristics of the technique include, (a) The creation of 3D patterned corrugated metamaterials with pattern resolution limited only by that of planar lithography. Since planar lithography is highly versatile, a variety of patterns with different sizes and shapes can be formed. (b) The hands-free and wire-free self-folding of these materials use two orthogonal forces derived from the release of residual stress and the minimization of surface tension. Hence, this process is highly parallel and scalable allowing such materials to be mass produced. (c) Finally, the edges of the materials self-align and seal due to capillary forces of the liquid hinges—this self-sealing enhances overall rigidity and strength of the materials.

Consequently, the self-folding of patterned and sealed “egg-crate” shaped metamaterials was realized. Patterns were incorporated in the form of “smart” patches on the walls of the egg-crates which can be selectively functionalized with biomolecules. Apart from the intellectual appeal of these hands-free, self-sealing materials, we envision applicability of these egg-crate like microstructures in lab-on-a-chip assays as functionalized microwells and as light weight mechanical metamaterials.

Solution-based fabrication methods have been widely used for depositing uniform functional coatings. These coatings can be utilized in a variety of applications such as optoelectronics, biomedical, and energy. However, such fabrication techniques are not appropriate for directly depositing patterned micro/nano-scale features, which are required in many contact-based applications such as in MEMS.

In this work we propose the direct writing of hydrophobic silica-based sol-gel patterns with sustained functionality and their subsequent tribological characterization. Such an approach may be an advantageous alternative to current lithography-based methods due to the relative ease of processing and low material waste. This investigation involves the abrasive wear and frictional analysis of patterned fluorinated silica sol-gel coatings that are directly printed onto glass substrates with a robotically controlled pneumatic nozzle system. Such work sheds light on the tribological properties of lithography-free processed hydrophobic patterns for applications spanning from micromotors to biomedical fluidic devices.

Conducting polymers are often employed as coatings on smooth metal electrodes to improve the electrode performance with respect to the signal-to-noise ratio for neural recording, charge-injection capacity for neural stimulation, and inducement of neural growth for electrode-tissue integration. However, adhesion of conducting polymer coatings on metal electrodes is poor, making the coating less durable and the electrical property of the electrode less stable. Moreover, conventional conducting polymers have relative low conductance, preventing their direct use as the electrode and lead material; and they are brittle, making it difficult for flexible neural electrodes to incorporate conducting polymer coatings. We have developed a new polypyrrole/polyol-borate composite film with concurrent excellent electrical and mechanical properties. We further developed a method to fabricate a stretchable multielectrode array using this new material as the sole conductor for both electrodes and leads, in contrast with the conventional approach of incorporating conducting polymers only through coating on non-stretchable metal electrodes. The resulting stretchable polymeric multielectrode array (SPMEA) was stretchable up to 23% uniaxial tensile strain with minimal losses in electrical conductivity. Electrochemical testing revealed the SPMEA’s impressive advantage for recording local field neural potentials and for epimysial stimulation of denervated skeletal muscles. As a neural interface engineer, I would also like to compare the compliant neural interfacing technology to other technologies, such as optogenetics, radiogenetics, and even a living neural interface that is currently under development in our lab.

An urgent need exist for developing handheld devices for rapid, sensitive, and specific detection method for pathogens. Here we demonstrate a rapid detection method for Gram-positive and Gram-negative bacteria using an impedance sensor array functionalized with antimicrobial peptides (AMPs). This impedance sensor screens pathogens in real-time and has comparable sensitivity with current detection methods like polymerase chain reaction (PCR) and immunoassay. Functionalized electrodes in array selectively bind to the corresponding bacteria strains, resulting in variations in the impedance modulus. Impedance variation is used to detect incubated bacterial cell concentration with a resolution of 1 cell µL-1. The dynamic range of detection for both Gram-positive and Gram-negative bacteria is found to be 103-106 cfu mL-1. Micropatterned electrodes modified with AMPs in an impedimetric array offer an excellent platform for rapid and selective detection of pathogens in contaminated water and food products.

Diamond, because of its unique physical, chemical, and electrical properties and the feasibility of growing it in thin-film form, is an ideal choice as a material for the fabrication of reliable, long endurance, microelectromechanical/nanoelectromechanical systems (MEMS/NEMS). However, various practical challenges, including wafer-scale thickness uniformity, CMOS compatibility, surface micromachining, and, more importantly, controlling the internal stress of the diamond films, make this material more challenging for MEMS engineers. Recent advances in the growth of diamond films using chemical vapor deposition have changed this landscape since most technical hurdles have been overcome, enabling a new era of diamond-based MEMS and NEMS development. This article discusses a few examples of MEMS and NEMS devices that have been fabricated using mono-, nano-, and ultrananocrystalline diamond films as well as their performance.

“Smaller is stronger.” Nanostructured materials such as thin films, nanowires, nanoparticles, bulk nanocomposites, and atomic sheets can withstand non-hydrostatic (e.g., tensile or shear) stresses up to a significant fraction of their ideal strength without inelastic relaxation by plasticity or fracture. Large elastic strains, up to ∼10%, can be generated by epitaxy or by external loading on small-volume or bulk-scale nanomaterials and can be spatially homogeneous or inhomogeneous. This leads to new possibilities for tuning the physical and chemical properties of a material, such as electronic, optical, magnetic, phononic, and catalytic properties, by varying the six-dimensional elastic strain as continuous variables. By controlling the elastic strain field statically or dynamically, a much larger parameter space opens up for optimizing the functional properties of materials, which gives new meaning to Richard Feynman’s 1959 statement, “there’s plenty of room at the bottom.”

The measurement of precise submicron displacements is essential in several MEMS applications. For instance, the measurement of the mechanical parameters of biological cells requires repeatable measurement of displacements in the nanometer regime. This paper presents a method to make displacement measurements in an aqueous MEMS environment with a ± 10 nm accuracy by using the blue channel of RGB pictures in combination with a FFT phase shift analysis.

Electrokinetic based micro- and nanofluidic technologies provide revolutionary opportunities to separate, identify and analyze biomolecular species. Key to fully harnessing the power of such systems is the development of a robust method for integrated electrodes as well as a thorough understanding of the influence of the electrokinetic surface properties with and without different surface modifications. In this work, we demonstrate a surface micromachined fabrication approach for integrated addressable metal electrodes within centimeter-long nanofluidic channels using a low-temperature, xenon diflouride dry-release method for novel biosensing applications, as well as recent results from a joint theoretical and experimental study of electrokinetic surface properties in nano- and microfluidic channels fabricated with fused silica. The main contribution of this fabrication process involves the addition of addressable electrodes to a novel dry-release channel fabrication method, produced at <300°C, to be used in nanofluidic electronic sensing of biomolecules. Finally, we also show a novel method with which to coat our channels with silane based chemistries. Certain modifications are observed to show improved resistance to non-specific adhesion of both small molecules and proteins, indicating their further use as compatible surfaces in micro- and nanofluidic applications.