Anchor losses significantly limit the quality factor (Q) in MEMS resonators such as gyroscopes. This work demonstrates a zero-energy diamagnetic levitation scheme for a Dual-Shell Resonator Gyroscope (DSG), using a custom 3D-printed NdFeB magnet and pyrolytic graphite stabilizers for passive, contactless support. Stable levitation of a similar to 1.1 g mass is achieved with a 3.8-4.4 mT magnetic field and -71 mu T/mm gradient, while integrated coils enable PID-controlled height adjustment (similar to 750 mu m range) at similar to 1.9 mW. Under AC drive near 20 kHz, out-of-vacuum vibration amplitudes remain limited by air damping, but simulations predict significantly larger resonant responses in vacuum. This compact, low-power approach offers a promising avenue for high-Q inertial sensing.

This article presents a novel way to estimate magnetodielectric composites’ complex permittivity ( $\varepsilon $ ) and permeability ( $\mu$ ). A methodology based on artificial neural network (ANN) modeling is proposed to determine $\varepsilon $ and $\mu$ from $S$ -parameter measurements around 2.45 GHz, obtained using a new microstrip split ring resonator (SRR)-based resonant sensor.

In this work, we synthesized nanoparticles of the Ni1-xCoxFe2O4 (with x = 0.25, 0.50, and 0.75) inverse spinel by the hydrothermal method. Scanning transmission electron microscopy (STEM) analysis and elemental characterization revealed the formation of nanoparticles of the order of similar to 3 nm with a homogeneous distribution of their constituents, denoting the correct material synthesis. The results show that as the content of Co2+ increases, the cell parameter of the structures increases and the crystallite size increases. Besides, the magnetic characterization exhibits an increase in the saturation magnetization as the Co2+ content moves from x = 0.25 to x = 0.75, on the other hand, the coercive field decreases, which is attributed to the superparamagnetic behavior of the structures. By Density Functional Theory (DFT) calculation demonstrates that the inverse spinel is the most favorable configuration for both NiFe2O4 and CoFe2O4 compounds. Besides, by first-principles thermodynamics, we have shown that Co tends to occupy the Ni sites as the most favorable configuration, with an increase in the cell parameter and total magnetization as Co content increases, in excellent agreement with experimental measurements. Our findings demonstrate that Co-Ni-based ferrites are soft magnetic materials, which are suitable candidates to be employed in devices that require rapid magnetization and demagnetization

Aquatic Robots have a critical role to enhance oceanography studies, enable search and rescue scenarios, and basically enable performing tasks that without them, would be too dangerous or even impossible for humans alone. Among the different types of Aquatic prototypes, robots with laser-following features offer enhanced precision, adaptability, simplified guidance, object tracking, and research opportunities due to their suitability for multiple applications. Thereby, this paper explores the design and implementation of an Autonomous Aquatic Robot, capable of following a laser beam through an arrange of multiple RGB sensors feeding an embedded Artificial Neural Network (ANN), optimally trained through a metaheuristic algorithm (Earthquake Optimization Algorithm) to create a laser-following robot. Experimental results validate how Artificial Intelligence (AI) can be applied to generate a control structure for a laser-following robot, with over 99% of accuracy to generate activation signals by the laser presence detection, to provide a reliable signal for the autonomous prototype.

Static coordinates can be convenient to solve the vacuum Einstein's equations in presence of spherical symmetry, but for cosmological applications comoving coordinates are more suitable to describe an expanding Universe, especially in the framework of cosmological perturbation theory (CPT). Using CPT we develop a method to transform static spherically symmetric (SSS) modifications of the de Sitter solution from static coordinates to the Newton gauge. We test the method with the Schwarzschild de Sitter (SDS) metric and then derive general expressions for the Bardeen's potentials for a class of SSS metrics obtained by adding to the de Sitter metric a term linear in the mass and proportional to a general function of the radius. Using the gauge invariance of the Bardeen's potentials we then obtain a gauge invariant definition of the turn around radius. We apply the method to an SSS solution of the Brans-Dicke theory, confirming the results obtained independently by solving the perturbation equations in the Newton gauge. The Bardeen's potentials are then derived for new SSS metrics involving logarithmic, power law and exponential modifications of the de Sitter metric. We also apply the method to SSS metrics which give flat rotation curves, computing the radial energy density profile in comoving coordinates in presence of a cosmological constant.

Objective: The objective of this study is to design a physical model of a magnetic filtration system which can separate magnetic nanoparticle (MNP)-tagged cytokines from fluid at physiologically relevant flow rates employed during cardiopulmonary bypass (CPB) procedures. Methods: The Navier-Stokes equations for the pressure driven flow in the chamber and the quasistatic stray magnetic field produced by an array of permanent magnets were solved using finite element analysis in COMSOL Multiphysics for 2D and 3D representations of the flow chamber. Parameters affecting the drag and magnetic forces including flow chamber dimensions, high gradient magnet array configurations, and particle properties, were changed and evaluated for their effect on MNP capture. Results: Flow chamber dimensions which achieve appropriate flow conditions for CPB were identified, and magnetic force within the chamber decreased with increased chamber height. A magnetic "block" array produced the highest magnetic force within the chamber. Polymeric microparticles loaded with MNPs were shown to have increased particle capture with increased hydrodynamic diameter. Conclusion: The model achieved a predicted efficiency up to 100% capture in a single-pass of fluid flowing at 1.75 L/min. Significance: This work is an important step in designing a magnetic flow chamber that can remove the magnetically tagged cytokines under high flow employed during CPB. Cytokines have been shown to stimulate the systemic inflammatory response (SIR) associated with CPB and are an established therapeutic target to mitigate the SIR. In the long term, this work aims to guide researchers in the more accurate design of magnetic separation systems.

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 μm long thermal actuators showed a maximum displacement of 18.0 μm at 8.31mW and reliably actuated up to 8,500 cycles. An interdigitated electrostatic comb-drive actuator was also successfully demonstrated, displacing 12.7 μm when 160V was applied. Finally, a 3D actuated mechanism was designed by incorporating a thermal actuator with 3D compliant mechanisms to flap 250 μm long wings. Flapping motion was successfully demonstrated. [2020-0010].

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 μm 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 μm 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.

The measurement of the size of gravitationally bounded structures is an important test of gravity theories. For a given radius different theories can in fact predict a different gravitational stability mass (GSM) necessary to ensure the stability of the structure in presence of dark energy. We compute the GSM of gravitationally bounded structures as a function of the radius for different scalar-tensor theories, including $f(R)$ and generalized Brans-Dicke, and compare the theoretical predictions to observational data. Since the GSM only gives a lower bound, the most stringent constraints come few objects with a mass lower that the one expected in general relativity. The analysis of different observational data sets shows that modified gravity theories (MGT) are compatible with observational data, and in some cases fit the data better than general relativity (GR), but the latter is not in strong tension with the observations. The data presently available does not provide a conclusive evidence of the need of a modification of GR, with the largest deviation of order $2.6 \,\sigma$ for the galaxy cluster NGC5353/4. Future data from galaxy surveys such as the Euclid mission could be important to get stronger constraints.

This work demonstrates two strategies to reduce the energy required for actuation of thin film NiTi unimorph actuators with 3D printed polymeric passive layers. First, by taking advantage of 3D printing, a low mass and high stiffness passive layer can be used to achieve faster heating/cooling rates. This ultimately reduces the time and energy required to achieve a threshold temperature. The second approach uses higher currents for shorter periods of time to reach a predefined operational temperature with less energy. Using a well-designed 3D printed passive layer combined with pulsed actuation results in a decrease in the required input energy per cycle of approximately 83 % while improving the mechanical work output by about 50 % when compared to actuators with a solid passive layer driven at a lower current. The actuators were tested using currents up to 19 mA, aiming for a 95 °C change in the temperature of the NiTi layer. The proposed strategies have been shown to enhance the energy efficiency of the electrothermally heated NiTi unimorph microactuators by up to 803 %. [2020-0204]

This work presents the design, modeling, and fabrication of a whisker-like sensor capable of measuring the whisker’s angular displacement as well as the applied moments at the base of the whisker. The sensor takes advantage of readily accessible and low-cost 3D magnetic sensors to transduce whisker deflections, and a planar serpentine spring structure at the whisker base is used to provide a mechanical suspension for the whisker to rotate. The sensor prototype was characterized, calibrated, and compared with analytical models of the spring system and the magnetic field. The prototype showed a moment sensing range of 1.1N·mm when deflected up to 19.7°. The sensitivity of the sensor was 0.38°/LSB for the angular displacement sensing, and 0.021 Nmm/LSB for the moment sensing. A fully integrated system is demonstrated to display real-time information from the whisker on a graphical interface.

This paper explores a method for incorporating samarium cobalt (both Sm2Co17 and SmCo5) inclusions into screen-printed barium hexaferrite (BaFe12O19) films in order to tune the ferromagnetic resonance (FMR). Using an all-low-temperature screen-printing process, >140-mu m-thick composite films are fabricated using heterogeneous mixtures of magnetic particles in a polydimethylsiloxane (PDMS) binder. RF characterization is performed using two-port S-parameter measurements on a coplanar waveguide (CPW) with external magnetic bias fields. The films exhibit a self-biased FMR response that ranges from 41 to 53 GHz (12-GHz span) by varying the relative ratio of the hexaferrite and Sm-Co particles. These effects are attributed to the embedded Sm-Co particles providing additional internal field bias acting on the barium ferrite.

We report the design, fabrication, and experimental characterization of the first fully 3D-printed, multi-material miniature magnetic actuators for compact systems in the literature. The actuator design integrates a bonded hard magnet made of NdFeB microparticles embedded in a Nylon 12 matrix (55% by volume) with structural and support elements made of pure Nylon 12. The device is a 10 mm-diameter, 1.2 mm wallthick, and 9 mm tall cylindrical frame that mounts on an off-theshelf solenoid and a 10 mm diameter, 100 mu m-thick, leak-tight membrane connected at its center to a 4 mm diameter, 4.95 mm tall hard magnet. The actuators are monolithically printed in layers as thin as 100 mu m using 600 mu m-wide strokes via fused filament fabrication (FFF) -a low-cost 3D printing technology capable of processing high-performance thermoplastics to create monolithic objects made of a plurality of distinctive feedstock. The average surface roughness, Young's modulus, and hardness of the FFF-printable hard-magnetic filament were estimated at 58.55 mu m, 3.59 GPa, and Shore D 71.5, respectively, while the average surface roughness, Young's modulus, and yield strength of FFF-printed magnetic material were estimated at 5.79 mu m, 2.02 GPa, and 55.99 MPa +/- 4.59 MPa, respectively. Magnetic characterization of the FFF-printed NdFeB-embedded Nylon 12 feedstock demonstrates the fabrication of isotropic hard magnets with an intrinsic coercivity of similar to 700 kA/m, remanence of similar to 395 mT, and a maximum energy product of 27 kJ/m(3). Simulations of the stray magnetic field produced by a printed sample made of NdFeB-embedded Nylon 12 were validated using a scanning Hall probe. The vertical displacement of a miniature 3D-printed magnetic actuator was characterized with a solenoid for various coil bias voltages; a maximum displacement equal to 50 mu m was obtained with 3.1 V DC applied to the driving coil. Finite element simulations of the actuator design estimate at 2.38 MPa the maximum stress on the membrane at 50 mu m actuation (i.e., below the fatigue limit of Nylon 12), and at 592.61 Hz the natural frequency of the device, which was corroborated via experiment. [2018-0288]

This paper reports the fabrication and characterization of thick, self-biased hexaferrite magnetic structures patterned on planar substrates for integrated millimeter-wave (mm-wave) device applications. Using all lowtemperature processes, BaFe12O19 micro/nanoparticles (from three different vendors) and polymeric binder (PDMS) are screenprinted into removable molds to form 600-μm-diameter, 144-μm-thick test structures. The crystallography, morphology, and DC magnetic hysteresis curves are evaluated. Methods are shown for imposing magnetic anisotropy in the films. A direct measurement of the RF properties using a coplanar waveguide test structure is performed, showing a ferromagnetic resonance (FMR) frequency of 45.9 GHz with tunability via an external magnetic field.

This paper reports the batch fabrication of magnetically patterned bases for millimeter-scale, diamagnetically levitated microrobots.A selective-magnetization process is used to imprint checkerboard magnetic pole patterns in a single NdFeB substrate.Further machining of the substrate produces nine microrobots per batch (limited by the surface area of the magnetic substrate).This process represents a leap forward compared to the current fabrication approach, which relies on hand-assembly and gluing arrays of discrete magnets.The diamagnetic repelling forces of bases with two thickness (400 μm and 280 μm) are directly measured (227 μN and 64 μN), showing that the thicker base produced higher force.Furthermore, the microrobots are capable of assisted levitation (external magnetic field bias) and operation in sliding mode (lateral movement) using microfactory drive platform.

Gift cards are an increasingly popular payment platform. Much like credit cards, gift cards rely on a magnetic stripe to encode account information. Unlike credit cards, however, the EMV standard is entirely infeasible for gift cards due to compatibility and cost. As such, much of the fraud that has plagued credit cards has started to move towards gift cards, resulting in billions of dollars of loss annually. In this paper, we present a system for detecting counterfeit magnetic stripe gift cards that does not require the original card to be measured at the time of manufacture. Our system relies on a phenomenon known as jitter, which is present on all ISO/IEC-standard magnetic stripe cards. Variances in bit length are induced by the card encoding hardware and are difficult and expensive to reduce. We verify this hypothesis with a high-resolution magneto-optical microscope, then build our detector using inexpensive, commodity card readers. We then partnered with Walmart to evaluate their gift cards and distinguished legitimate gift cards from our clones with up to 99.3% accuracy, Our results show that measurement and detection of jitter increases the difficulty for adversaries to produce undetectable counterfeits, thereby creating significant opportunity to reduce gift card fraud.

This work describes the simulation, batch fabrication, functional demonstration, and magnetic field/force characterization of highly miniaturized ∼3.8 mm3 axisymmetric electropermanent magnets (EPMs). Two different bonded high-coercivity, rare-earth permanent magnet powders (∼15 µm Sm2Co17 particles and 6 µm NdFeB particles) were evaluated for the fabrication of the fixed magnets in the EPM, reaching latching force on/off ratios of 191:1 and 303:1 respectively. Compared to conventional side-by-side architecture, the axisymmetric design provides: 1) symmetric magnetic field along the magnetization axis, as opposed to the asymmetric fields in the typical transverse configuration, 2) higher and controllable latching force in a smaller volume, and 3) a path for further batch-microfabrication and system integration.

A portable microelectromechanical system (MEMS) for mobile phones, or other portable devices, that measures body electrical signals, as well as, extracts transdermal biological fluid for invivo analysis is proposed. This system integrates two sensing methods: three points finger electrocardiography (ECG) and glucose monitoring, through one electrode with a microneedle-array. This work presents the: (1) device modeling and microneedle-array' fabrication method, (2) signal processing and biasing circuitry' design and simulation, (3) Analog Front End (AFE) for measured signals, and (4) Glucose sensor characterization. Design parameters and geometries are obtained by solving the capillarity model inside the microneedles and running optimization numeric methods. The AFE consists in a differential band pass filter that provides amplification, filtering, and noise rejection. This work presents clear technological innovation, for its miniaturization and integration of known biological signals' measurement methods in a portable Smart System, which points in the direction of Internet of Things' goals.

This paper describes the direct measurement and mapping of magnetic forces/fields with microscale spatial resolution by combining a commercial microforce sensing probe with a thin-film permanent micromagnet. The main motivation of this work is to fill a critical metrology gap with a technology for direct measurement of magnetic forces from nN to 10’s of mN with sub-millimeter spatial resolution. This capability is ideal for measuring forces (which are linked to magnetic field gradients) produced by small-scale magnetic and electromagnetic devices including sensors, actuators, MEMS, micromotors, microfluidics, biomedical devices. This new measuring technique is validated by comparison of measured forces from small permanent magnets with the analytical models.