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Small-scale flexible (or compliant) mechanisms are valuable in replacing rigid components while retaining comparable motion and behavior. However, fabricating such mechanisms on this scale (from 0.01 to 10 cm) proves difficult, especially with thin sheet metals. The manufacturing method of laser forming, which uses a laser to cut and bend metal into desired shapes, could facilitate this fabrication. However, specific methods for designing mechanisms formed by lasers need to be developed. This work presents laser forming as a means for creating compliant mechanisms on this scale with thin sheet metal. The unique challenges for designing mechanisms to be laser formed are explored, and new adaptations of existing designs are fabricated and discussed. The design of basic “building-block” features is developed for several mechanisms: a parallel-guided mechanism, a cross-axis flexural pivot, a lamina emergent torsional (LET) joint array, a split-tube flexure, and a bi-stable switch. These mechanisms are shown to perform repeatable behavior and motion comparable to existing nonlaser-formed versions. The further possibilities for fabricating compliant mechanisms with laser forming are explored, as advanced applications can benefit from using lasers to create compliant mechanisms from thin sheet metal.

Shape memory alloy (SMA) actuators can provide significant advantages for small-scale robotics given their robustness, energy density, and low voltage actuation. However, NiTi thin films typically found in SMA microactuators do not often provide useful forces and displacements for microrobotic applications. This work presents a fabrication process in which NiTi thin film actuators are integrated with two-photon polymerization (TPP) 3D printing to scale these actuators up for use in mesoscale systems. Individual unimorph actuators are characterized with respect to uniformity across many actuators so that actuators can be arrayed together for even larger forces or combined toward the operation of complex mechanisms. The resulting actuators are fast to prototype, reliable and stable (up to 5000 cycles), and can utilize complex geometries that are otherwise challenging to achieve with conventional MEMS microfabrication techniques. A 2D positioner is demonstrated by combining six individually controlled actuators with conventional mm-scale fabrication techniques (3D stereolithography printing, wire bonding and PCB assembly). The actuators are controlled by a commercial microcontroller and powered using a standard Lithium polymer battery. [2020-0208]

The fabrication and integration of microactuators with 3D micromechanisms are necessary to develop microrobots with higher capability and complexity. In this work, a two-step fabrication method combining 3D printing with two-photon polymerization (TPP) and aluminum sputtering is demonstrated. Actuators using two different transduction mechanisms (thermal and electrostatic) were fabricated in this process, and a thermal actuator was printed with a mechanism in three-dimensional space without additional assembly steps. This work also provides parameterized characterizations which can be used as design guidelines for building actuators and mechanisms. A design approach to electrically isolate the actuators from the substrate is introduced so that the device can be functional after two fabrication steps without patterning the metal layer. Metal coverage on the sidewalls of trenches are characterized, which provides a design space for deciding electrode gaps and heights in electrostatic actuators. Using these guidelines, 500 $\mu \text{m}$ long thermal actuators showed a maximum displacement of 18.0 $\mu \text{m}$ at 8.31mW and reliably actuated up to 8,500 cycles. An interdigitated electrostatic comb-drive actuator was also successfully demonstrated, displacing 12.7 $\mu \text{m}$ when 160V was applied. Finally, a 3D actuated mechanism was designed by incorporating a thermal actuator with 3D compliant mechanisms to flap 250 $\mu \text{m}$ long wings. Flapping motion was successfully demonstrated. [2020-0010]

NiTi thin films with robust shape memory effects and low deposition temperatures are greatly desired for microelectronic devices. However, sub-micron films deposited below 425 °C usually have amorphous structure and must be post-annealed to achieve full crystallization. In this article, using Ru as a seed layer, we demonstrate growth of NiTi films as thin as 120 nm with in-situ crystallization at 325 °C. NiTi thin films with a wide range of growth parameters including deposition temperature and film thickness were investigated. Shape memory effects were characterized using stress bow and resistivity studies. Structural information across the R-phase to austenite transformation was obtained using X-ray diffraction. NiTi thin films exhibited a narrow hysteresis during R-phase to austenite phase transition near 60 °C while possessing good shape memory properties.

NiTi SMA thermal bimorph actuators have potential as high-force, high-displacement MEMS actuators. Historically, even microscale SMA actuation response has been limited to a maximum of ˜100 Hz. As NiTi film and device dimensions are scaled down into the micro and nano scales, heat transfer, and thus device cycling speeds can be significantly improved upon. We have used an in-situ annealed nickel-titanium (NiTi) shape memory alloy (SMA) sputter deposition process to sputter equiatomic NiTi films at 600 °C. We characterized our thin film (270 nm NiTi – 1.6 μm NiTi) material and verified its reversible shape memory effects (SME) using differential scanning calorimetry (DSC), X-ray diffraction (XRD), and wafer bow versus temperature measurements. Upon release, the NiTi material exhibited a reversible phase change around 60 °C with a hysteresis of ˜3 °C. For the substrate confined case (i.e. NiTi on Si or Pt), hysteresis was much larger (i.e. ˜40 °C) with the phase change completed at ˜80 °C. In addition to SMA material characterization, we fabricated NiTi/Pt bimorph actuators at several (100 nm to 1.2 μm) NiTi and Pt thicknesses. Free-standing bimorph actuators were produced via a dry etch release, and temperature dependent curvature of these cantilevers was investigated. To address the low power, and high response time aspects, we performed a dynamic characterization using a 440 mW, 532 nm “green” laser to irradiate devices from 2 to 24 W/cm2 while measuring actuation response times that varied from 3 ms at the highest irradiation fluxes to 240 ms at the lowest. Our results showed decreased actuation powers and faster heating or actuation times compared to past works with NiTi microactuators. The NiTi films with 600 nm thickness on top of 20 nm Pt films exhibited the greatest change in curvature from 200 μm to flat states, and actuated in under 3 ms due to the very small volume of SMA requiring to be heated. These results suggest that NiTi/Pt bimorphs have potential applications as lower-power, faster-response, laser-activated micro shutters or thermal switches without needing a traditional wired power source.

Combining electrical and magnetic materials in the same part has been a challenge in 3D printing due to difficulties co-printing complex materials in many additive manufacturing processes. Past 3D printed inductors and other similar magnetic devices have therefore either lacked the magnetic materials necessary for improved performance, or required sintering at high temperatures for extended periods, beyond the capability of most 3D printable polymers. In this work, we demonstrate a room temperature process for incorporating conductive and magnetic materials into the same 3D printed device. A multi-stage fabrication process based on 3D printing followed by fill with magnetic and conductive fluids is proposed. Multi-layer microfluidic channels for magnetic passives are first printed in a stereolithography process. The microfluidic systems are then filled with room temperature liquid metal, a gallium alloy liquid at room temperature, and ferrofluid to create inductors, transformers and wireless power coils. Through the addition of ferrofluid as a magnetic material, increases in inductance density by nearly a factor of three were demonstrated, in addition to coupling improvements for transformer and wireless power coils compared to the devices before magnetic fill.

Well-controlled, focused electron-beam induced etching of copper thin films has been successfully conducted on bulk substrates in an environmental scanning electron microscope by controlling liquid-film thickness with an in situ correlative interferometry system. Knowledge of the liquid-film thickness enables a hybrid Monte Carlo/continuum model of the radiation chemistry to accurately predict the copper etch rate using only electron scattering cross-sections, radical yields, and reaction rates from previous studies. Etch rates depended strongly on the thickness of the liquid film and simulations confirmed that this was a result of increased oxidizing radical generation. Etch rates also depended strongly, but non-linearly, on electron beam current, and simulations showed that this effect arises through the dose-rate dependence of reactions of radical species.

This work demonstrates the first sputtered thin-film nickel-titanium (NiTi) shape-memory alloy (SMA) actuators combined with direct 3D printing of polymeric structures. Resulting actuators are fast to prototype, reliable and stable (up to 5000 cycles), and can utilize complex geometries challenging to achieve with conventional MEMS microfabrication. The actuator design uses 3D printed polymer as the passive layer in unimorph actuators, adding significant versatility to the actuator design. An actuator designed for high force-displacement was fabricated with a $15\ \ \mu \mathrm{m}$ thick polymer layer and characterized by applying currents up to 18 ma (7.3 mW, producing ∼156°C) resulting in a maximum displacement of $3.3\ \mu \mathrm{m}$ and ∼0.9 mN blocking force. Dynamic operation with falling/rising times of 20.1 ms/9.8 ms and 33.5 Hz maximum operation frequency was also demonstrated.

Origami manufacturing, the use of folding to create 3-D shapes using 2-D fabrication tools and techniques, is a promising avenue for creating low cost parts. In this letter, we demonstrate the hands-free cutting and folding of 3-D inductor geometries from blank metal foil using only a 2-D laser cutter. Laser forming, localized laser heating to create thermal stresses to deform a workpiece, is used to fold traces out of plane without manual handling. The laser forming of thin copper foil is first characterized, followed by cutting and folding of two 3-D inductors: a three-turn planar coil with folded overpass and a twelve-turn toroid. The planar coil was found to have inductance 199 nH and peak quality factor of 99.7 at 54.7 MHz, while the toroid had inductance 159 nH with peak quality factor 64.9 at 86.7 MHz. With laser cutters, one of the most widely available machine tools, this technology allows custom, high performance electrical passives to be rapidly fabricated without specialized equipment.

Direct-write laser grayscale lithography has been used to facilitate a single-step patterning technique for multilayer lead zirconate titanate (PZT) thin films. A 2.55- $\mu \text{m}$ -thick photoresist was patterned with a direct-write laser. The intensity of the laser was varied to create both tiered and sloped structures that are subsequently transferred into multilayer PZT(52/48) stacks using a single Ar ion-mill etch. Traditional processing requires a separate photolithography step and an ion mill etch for each layer of the substrate, which can be costly and time consuming. The novel process allows access to buried electrode layers in the multilayer stack in a single photolithography step. The grayscale process was demonstrated on three 150-mm diameter Si substrates configured with a 0.5- $\mu \text{m}$ -thick SiO2 elastic layer, a base electrode of Pt/TiO2, and a stack of four PZT(52/48) thin films of either 0.25- $\mu \text{m}$ thickness per layer or 0.50- $\mu \text{m}$ thickness per layer, and using either Pt or IrO2 electrodes above and below each layer. Stacked capacitor structures were patterned and results will be reported on the ferroelectric and electromechanical properties using various wiring configurations and compared to comparable single layer PZT configurations.

Origami-inspired folding is a well-established method for creating 3D shapes from two dimensional sheets. Here we demonstrate for the first time using a laser to fold, assemble and propel the resulting free-moving part, all without any need for handling. Being able to remotely assemble and move complex parts is an important manufacturing innovation, with potential for controlling doors and latches as well as launching parts off of the build platform without direct assistance. Beginning with only a blank sheet of metal, the parts are first cut and folded using laser forming, where a laser is used to create localized plastic stresses to bend the workpiece. After dropping into place with a final cut, the resulting rotor is actuated with laser ablation propulsion, using a jet of ablated material to apply thrust.

Fused filament fabrication (FFF) 3D printers have been largely limited to thermoplastics in the past but with new composite materials available on the market there are new possibilities for what these machines can produce. Using a conductive composite filament, electronic components can be manufactured but due to the filament’s relatively poor electrical properties, the resulting traces are typically highly resistive. Selective electroplating on these parts is one approach to incorporate materials with high conductivity onto 3D-printed structures. In this paper, non-conductive and conductive filaments printed in the same part are used to enable selective electroplating directly on regions defined by the conductive filament to create metallic parts through 3D printing. This technique is demonstrated for the creation of multiple distinct conductive segments and to electroplate the same part with multiple metals to, for instance, allow a magnetic metal such as nickel and a highly conductive one such as copper to be incorporated in the same part. Following the characterization of the process, a representative 3D printed electrical device, a selectively electroplated solenoid inductor with low frequency inductance and resistance of 191 nH and 18.7 mΩ respectively was manufactured using this technique. This is a five order of magnitude reduction in resistance over the original value of 3 kΩ for the inductor before electroplating.

When infused with an oxidizer, on-chip porous silicon (PS) shows tremendous potential as an energetic material. However, applications such as fuzing and propulsion require long-term material stability. The present work utilizes accelerated lifetime testing for PS samples with sodium perchlorate (NaClO4) oxidizer. Devices were exposed to elevated temperatures for various time intervals, then subjected to an electrical pulse through an integrated bridgewire to test for ignition. The pass/fail data from ignition testing was then analyzed to determine the mean and median failure point at each temperature using an Arrhenius aging model and a lognormal probability density function (PDF). Samples were heated over a temperature range of 185–300 °C for up to 46 h with median failure times ranging from 0.4–20 h. Differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy were used to evaluate chemical changes of PS/NaClO4 during aging. Comparison of DSC traces for aged samples showed differences for heating above and below 250 °C, suggesting two different aging mechanisms. FTIR results suggest that for low temperature aging (below ∼250 °C) the hydrogen termination layer of the porous silicon was still intact, but backbond oxidation did occur. Above ∼250 °C the hydrogen termination layer was no longer evident in FTIR and considerable oxidation occurred, suggesting reaction or dissociation of the hydrogen layer. This corresponds with an exothermic peak shown during DSC at 300 °C. Thermogravimetric analysis/mass spectroscopy (TGA/MS) was also performed, and confirmed hydrogen gas release beginning at ∼280 °C. A DSC peak at ∼400 °C is evident for fresh samples, but is greatly reduced or not evident for all aged samples. We attribute this peak to backbond oxidation, which is shown to occur in FTIR for all aged samples. Variable heating rate DSC experiments were also performed to determine activation energy of fresh and aged samples. Activation energy was calculated using the Kissinger Method for the first two exothermic peaks in DSC experiments. For the first peak, corresponding to hydrogen desorption (∼300 °C), activation energy for fresh and aged samples was 132.1 kJ/mol and 132.7 kJ/mol, respectively. The activation energy of the second exothermic peak, corresponding to backbond oxidation, for fresh and aged samples was 183.8 kJ/mol and 159.6 kJ/mol, respectively. Device failure during accelerated aging tests was also used to predict the mean lifetime of porous silicon/sodium perchlorate at room temperature (25 oC) as 100 years with a 90% confidence interval of 31 to 328 years.

A new hands-free approach to antenna fabrication is presented here, with laser folding used to fabricate a prototype 94.5 GHz end-fed longitudinal shunt slot array (EFLSSA) antenna. Laser cutting and folding was demonstrated for creation of 3D metal antennas as a low cost, rapidly iterated alternative to machining techniques such as electro-discharge machining (EDM) and die forming. The technique used is based on a low cost and power 1064nm marking laser. All cutting and folding is done completely remotely using the laser itself from a blank sheet of metal foil. The demonstrated waveguide slots are cut to sub-micron precision, and modelling of the resulting structure is also presented.

The low conductivity of 3D printed conductive lines is one of the main obstacles in successful 3D printed electronics. These low conductivities lead to lossy transmission lines, poorly performing antennas, and pose many challenges from a circuit design prospective. In this work, two techniques are demonstrated for improving the conductivity of 3D printed silver paste: photonic sintering and selective electroplating. The silver lines were direct write extruded onto a FFF 3D printed substrate and dried before curing. As an alternative to traditional heat curing, parts printed on a uniaxial double sloped 3D surface are photonically sintered using a commercial PulseForge system, resulting in an increase of the line conductivity by 806%. The lines were then electroplated in a copper plating solution, selectively depositing a layer of copper to obtain a further increase in the line conductivity of 886%, a total improvement of 7,150%. Line conductivities were verified using a 4-point measurement setup along with an X-Ray CT scanning system to determine the cross sectional area of the lines. Bringing high resolution 3D printed metal lines closer to bulk conductivities is critical in enabling 3D printed RF and high performance electronics.

Bidirectional rotary motion of a millimeter-scale traveling wave ultrasonic motor is demonstrated using solution-deposited thin-film lead zirconate titanate and wafer-scale microelectromechanical system fabrication techniques. Rotation speeds of a motor 3 mm in diameter have been characterized up to 2000 r/min as a function of voltage, phase, and frequency, with power consumption less than 4 mW. Frequency characterization shows no nonlinear behavior, while phase characterization shows that motion can be generated with a single source drive. Furthermore, imprint in the piezoelectric response was exploited to achieve higher speeds, starting voltages lower than 4 V, and demonstration of a 2-mm diameter motor up to 1730 r/min. Design and fabrication of the motors are also presented.

Multilayer actuators (MLAs) offer an increase of force per unit area, a reduction in power consumption, and a reduction in required driving voltages compared with singlelayer actuators. For example, switching from a single 0.5- or 1.0-μm layer of PZT to multiple 250-nm-thick layers would enable a 2/3 to 3/4 reduction in actuation voltage and an increase of 2 to 3 times in actuation force per area for a PZT MEMS switches and robotics. Efforts have been focused on developing actuators using four 250-nm-thick layers of PZT with a Zr/Ti ratio of 52/48 (i.e., the morphotropic phase boundary). The PZT films used a previously established method of achieving greater than 98% (001/100) oriented PZT by chemical solution deposition (CSD). By performing X-ray diffraction measurements between each layer, the texture within the films could be monitored during the growth process. To electrically measure the quality of the PZT multilayer stack, a series of six-sided capacitors were fabricated. The devices were connected in parallel with an average dielectric constant of 1150 for each PZT layer and an average total capacitance of 45 nF. In addition to capacitors, cantilever actuators were fabricated to measure the piezoelectric induced deformation. Comparisons with 100-μm-long cantilever between a single 1-μm-thick PZT and four 250-nm-thick layer PZT stack have shown comparable displacements of |3.7| μm and |4.0| μm, respectively, with an applied electric field of 10 V/μm across the film. These measurements on MLA PZT films demonstrate high piezoelectric coefficients that are suitable for tactile radio and milimeterscale robotic devices.

We describe the design, modeling, fabrication, and testing of a MEMS inertial switch that can detect accelerations in the x, y, and z axes using a single mass/spring assembly (first reported in Ref. [1] ). A spiral spring suspension is used which is compliant in all directions. The inertial switch approach offers zero power draw until an acceleration event occurs. Arrays of individual triaxial sensors are created on a single chip, with each switch designed to close at a different acceleration threshold between 50 g and 250 g. A resistor ladder connects each switch together in series such that the number of pinouts from the chip is substantially reduced. The response of the switch array to half-sine acceleration pulses of 5–8 ms duration is reported, with multiple switches in the array closing and opening in sequence for higher magnitude acceleration pulses. The switch closure time under these conditions is consistently less than 200 μs, and bounce is minimal for applied accelerations lower than 200 g.

An integrated approach to the fabrication of thin-film piezoelectric traveling wave ultrasonic motors at the mm-scale is being developed for low power, high torque motors for small scale robotics, biomedical, and sensing applications. This paper describes the realization of ultrasonic motor stators ranging in diameter from 1 to 3 mm using wafer scale MEMS fabrication techniques with lead zirconate titanate (PZT) thin films. Using laser Doppler vibrometry (LDV), controlled traveling waves were demonstrated in the bulk silicon elastic medium of the stator and the standing wave behavior was characterized for control purposes. Furthermore, the resonant modes of the fabricated stators were modeled using finite element models, and experimental results agree well with this analysis.

In this work we discuss the design and fabrication of NiTi on Pt bimorph cantilever arrays that may be actuated by utilizing the martensite to austenite phase transformation of a sputtered thin film of equiatomic NiTi shape memory alloy (SMA). The cantilever devices were fabricated on a silicon wafer using standard micro fabrication techniques, and may therefore be applicable to microelectromechanical systems (MEMS) switch or actuator applications. This paper details the development of a co-sputtering process to yield a SMA film with controllable composition of Ni50Ti50 and transformation temperature around 60 °C. Shape memory effects were characterized and verified using Differential Scanning Calorimetry (DSC), which demonstrated a martensite-austenite phase change near 60 °C for a co-sputter deposited film onto a Si wafer at 600 °C for in-situ crystallization. We used wafer stress versus temperature measurements as additional confirmation for the repeatable measurement of reversible phase transformation which completed by 80 °C upon heating. Up to 900 MPa completely reversible stress change was available for actuation during the thermally induced phase change. The tightest curling devices were based on a 600 nm NiTi film on 20 nm Pt and were actuated between a 200 μm curl at 25 °C and flat states when heated beyond 70 °C. Using a 532 nm (green), 440 mW laser, we also characterized actuation times of NiTi on Pt cantilever actuators from 4–240 milliseconds using optical intensities ranging from 2–24 W/cm2.

Thin-film piezoelectric lead zirconate titanate (PZT) is one of the most efficient electromechanical coupling transducer materials currently available for microelectromechanical systems (MEMS). This article reviews piezoelectric MEMS (piezo MEMS) technologies using PZT thin films in radio frequency (RF) devices for communications and radar applications and in the emerging field of millimeter-scale robotics. The electromechanical material properties of thin-film PZT uniquely enable insect-inspired and insect-scale autonomous robots. Recent progress on large force and displacement actuators for robotic leg joints, compact and high torque ultrasonic motors, and bioinspired millimeter-scale flapping wing platforms will be presented. The use of thin-film PZT to achieve high performance and low-voltage RF MEMS switches, ultralow power consumption nanomechanical logic circuits, and high coupling and low loss resonators, filters, and transformers are also reviewed.

This review article presents recent advancements in the design and fabrication of thin-film (

Piezoelectric micromachined ultrasonic transducers (PMUTs) have the potential for broad bandwidth, thus enabling high resolution imaging. However, previous PMUTs had fractional bandwidths of only ∼50% or smaller because of the thick multilayer PMUT structure. Here, we demonstrate broadband PZT PMUTs that achieve a 97% fractional bandwidth by utilizing a thinner structure excited at two adjacent mechanical vibration modes. PMUTs were fabricated and characterized in the mechanical, electrical and acoustic domains, and a 30 µm × 200 µm ribbon PMUT demonstrates a large displacement sensitivity of 500 nm/V in air and pressure response of 0.3 kPa/V in fluid, equivalent to 13.6 kPa/V average pressure on the PMUT surface, measured 1.4 mm away from the PMUT.

Laser heating to generate plastic strains for controlled bending, known as laser forming, is a promising technique for creating 3D structures based on origami-inspired principles. Here, for the first time, laser cutting and forming are used to go from flat unpatterned metal sheet to final folded part, including up and down folds, all without manual handling. Folding direction is controlled by adjusting laser travel speed to create either a lateral or a vertical thermal gradient in the workpiece. Numerical modeling followed by experimental verification is used to determine the transition point between bending toward and away from the laser, followed by demonstration of a variety of complex 3D folded parts. Using this approach, laser forming is then used to precisely align two components, demonstrating the positioning of an optical reflector to guide the laser and pattern a portion of the sheeting originally inaccessible on the underside. All work here is done with a commercially available 20 W marking laser without modification.

A microelectromechanical system (MEMS) electric-field sensor (EFS) is presented in which the ambient electric field (E-Field) is modulated by vertical electrode displacement using lead-zirconate-titanate (PZT) piezoelectric actuators. The device is fabricated with a multi-layer copper-on-PZT process, which enables large (~10 μm) displacement and high aspect ratio electrode structures as needed for sensitive detection. The modulated displacement current between two electrodes, measured using a transimpedance amplifier, is proportional to the ambient, sensed E-Field. Fabricated EFS devices yielded a responsivity of 830 fA/(V/m) and a limit of detection down to 0.19 V/m/rtHz in vacuum (0.30 V/m/rtHz in air) with a 491-Hz E-field applied.

This paper reports theoretical analysis and experimental results on a numerical electrode shaping design technique that permits the excitation of arbitrary modes in arbitrary geometries for piezoelectric resonators, for those modes permitted to exist by the nonzero piezoelectric coefficients and electrode configuration. The technique directly determines optimal electrode shapes by assessing the local suitability of excitation and detection electrode placement on two-port resonators without the need for iterative numerical techniques. The technique is demonstrated in 61 different electrode designs in lead zirconate titanate (PZT) thin film on silicon RF micro electro-mechanical system (MEMS) plate, beam, ring, and disc resonators for out-of-plane flexural and various contour modes up to 200 MHz. The average squared effective electromechanical coupling factor for the designs was 0.54%, approximately equivalent to the theoretical maximum value of 0.53% for a fully electroded length-extensional mode beam resonator comprised of the same composite. The average improvement in S(21) for the electrode-shaped designs was 14.6 dB with a maximum improvement of 44.3 dB. Through this piezoelectric electrodeshaping technique, 95% of the designs showed a reduction in insertion loss.

Small autonomous aerial systems require the ability to detect roll, pitch, and yaw to enable stable flight. Existing inertial measurement units (IMUs) are incapable of accurately measuring roll-pitch-yaw within the size, weight, and power requirements of at-scale insect-inspired aerial autonomous systems. To overcome this, we have designed novel IMUs based on the biological haltere system in a microelectromechanical system (MEMS). MEMS haltere sensors were successfully simulated, designed, and fabricated with a control scheme that enables simple, straightforward decoupling of the signals. Passive mechanical logic was designed to facilitate the decoupling of the forces acting on the sensor. The control scheme was developed that efficiently and accurately decouples the three component parts from the haltere sensors. Individual, coupled, and arrayed halteres were fabricated. A series of static electrical tests and dynamic device tests were conducted, in addition to in-situ bend tests, to validate the simulation results, and these, taken as a whole, indicate that the MEMS haltere sensors will be inherently sensitive to the Coriolis forces caused by changes in angular rate. The successful fabrication of a micro-angular rate sensor represents a substantial breakthrough and is an enabling technology for a number of Army applications, including micro air vehicles (MAVs).

The authors report demonstrated bi-directional rotary motion of a millimeter scale traveling wave ultrasonic motor (TWUM) using thin film lead zirconate titanate (PZT). Rotation speeds of up to 2300 RPM have been achieved at 10V and less than 10mW. Design, fabrication, and initial testing of the TWUM are described. The low-power, high-torque, zero-power off state rotary motors described here, could enable numerous applications in the fields of small-scale robotics, fuzing, and biomedical technology.

Small autonomous aerial systems require the ability to detect roll, pitch, and yaw to enable stable flight. Existing inertial measurement units (IMUs) are incapable of accurately measuring roll-pitch-yaw within the size, weight, and power requirements of small autonomous systems. To overcome this, we have designed novel IMUs based on the biological haltere system in a microelectromechanical system (MEMS). MEMS haltere sensors were successfully simulated, designed, and fabricated with a control scheme that enables simple, straightforward decoupling of the signals. Passive mechanical logic was designed to facilitate the decoupling of the forces acting on the sensor. The control scheme was developed that efficiently and accurately decouples the three component parts from the haltere sensors. Individual, coupled, and arrayed halteres were fabricated. A series of static electrical tests and dynamic device tests were conducted, in addition to in-situ bend tests, to validate the simulation results, and these, taken as a whole, indicate that the MEMS haltere sensors will be inherently sensitive to the Coriolis forces caused by changes in angular rate. The successful fabrication of a micro-angular rate sensor represents a substantial breakthrough and is an enabling technology for a number of Army applications, including micro air vehicles (MAVs).

This paper reports on the design, fabrication, and testing of a 3-axis acceleration switch intended to serve as an early warning for traumatic brain injury (TBI). Mild TBI (colloquially termed “concussion”) resulting from rapid acceleration of the skull has been rising in the public consciousness with recently increasing awareness of the dangers and long-term health risks associated with it. The sensor described here is an array of acceleration switches designed to cover the range of acceleration associated with TBI, and to do so with no external power draw until an acceleration event within this range occurs.

An integrated approach to the fabrication of thin-film piezoelectric traveling wave ultrasonic motors (USMs) at the mm-scale is reported here for the first time. This paper describes the realization of ultrasonic motor stators ranging in diameter from 1–3 mm using wafer scale MEMS fabrication techniques. Using laser Doppler vibrometry (LDV), we have demonstrated traveling waves in the bulk silicon elastic medium of the stator. Furthermore, the resonant modes of the fabricated stators have been modeled, and experimental results agree well with these simulations.

Initial CFD simulations of quasi-steady hovering flight of the Drosophila sp. have studied the effects of delayed rotation of the wings at the end of each stroke and it s effect on the resulting unsteady aerodynamic forces found throughout the wing [8]. Further studies were carried out using the same CFD model as before to determine the lift and power requirements for Drosophila Virilis [7]. To verify the validity of the simulation s results, the specific power that was calculated (the sum of aerodynamic and intertial power requirements normalized to the fruitfly muscle mass) was compared to the values retrieved by Dickenson on tethered fruitflies [1]. Although the periodic behavior of the translational and rotational motions of the wing were heavily approximated, the comparison showed strong agreement. This lends support to the use of CFD models in the parametric design process used in the pioneering of microscale flapping wings [2]. It is of great importance to MEMs designers working on microscale flapping wing to study the detachment of Leading Edge Vortices (LEV). Solving the Navier-Stokes equations in the time-varying coordinates of the flapping wing proves a challenge computationally but offers the possibility of predicting the behavior of the LEV-shedding phenomenon to which flapping wings owe a majority of their lift. In addition to studying the shedding of LEVs, CFD simulations enable one to quickly assess the effect of wing shaping on vertical lift. Preliminary code was developed in MATLAB with these two potential studies in mind. The code that was developed to tackle the flapping wing problem solves the Navier-Stokes equations for a compressible fluid.

The ability to combine both actuation and sensing technologies into one unified MEMS fabrication process is enabling for a wide variety of applications including high frequency filters, transformers and mm-scale robotics. This research demonstrates piezoelectric MEMS (PiezoMEMS) devices based on lead zirconate titanate (PZT) thin films including switchable resonators, transformers, and microflight actuators with integrated strain sensors. PiezoMEMS resonators and transformers combine actuation and sensing on a single device platform. Current research on PZT based resonators is focused on optimizing the performance for both high quality factor, Q, and low motional resistance. Resonators in the low tens of MHz can also be utilized as piezoelectric resonant transformers and are predicted to achieve AC/DC gains in the range of 2 to 8. In addition, strain sensors positioned at the cantilever root of PiezoMEMS microflight actuators provide direct feedback of the motional response of the actuated wing.

A comparison of three different large-displacement microactuator technologies fabricated by deep reactive ion etching (DRIE) in silicon-on insulator (SOI) substrates is presented. Electrothermal, curved electrode electrostatic, and combdrive electrostatic actuator designs are considered, with each actuator design capable of producing more than 100 mm of displacement. Analytic models for each actuator type are reviewed, and both theoretical and experimental data for fabricated devices are analyzed and compared with respect to displacement, force, and power consumption.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.