Search Results (12)

Conventional LIG preparation mostly relies on the ablation process of a CO₂ laser on a polyimide (PI) substrate but is limited by the sensitivity of the laser parameters, which is prone to PI film deformation, non-uniformity of the process, or LIG surface breakage problems. In this study, we present a new method to fabricate superhydrophobic laser-induced graphene (SH-LIG) surfaces by immobilizing the polyimide (PI) film on the copper sheet, which enables uniform laser processing (single pass laser etching) over a wider range of microsecond laser parameters (10.5–19.5 W). Subsequently, the SH-LIG was obtained by vacuum-assisted immersion in stearic acid, resulting in a water contact angle greater than 150°, roll angle stabilized at 6°, and hydrophobic stability at a high temperature of 90 °C. Analysis by Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) showed that the LIG fabricated at optimal power (19.5 W) had a more developed C sp² network (I_2D/I_G ≈ 0.5) and pore structure, which significantly improved the photothermal conversion efficiency (up to 252 °C in air and 180 °C on water). On this basis, a simple micro-driver based on SH-LIG was designed. Experiments showed that the maximum velocity of the SH-LIG boat can reach an adjustable propulsion velocity of 45.6 mm/s (related to the laser processing power and the intensity of the driving light), which is 132% higher than that of the LIG boat. This work provides insights into the preparation of high-quality LIG and their application in photothermally driven micro actuators, highlighting the synergies between structural optimization, surface engineering, and photothermal performance. Full article

The use of vacuum-hybrid DC circuit breaking methods allows the short-circuit current to be switched off in a shorter time, resulting in a reduction in the arc burning time. This requires the use of a drive, such as the Thomson Coil Actuator TCA, capable of providing a short response time for opening the vacuum interrupter VI, regardless of its rated current. The IDD is powered by a pre-charged capacitor, which, together with the drive coil, forms an LC oscillating circuit that, when switched on by a thyristor, generates a current pulse of several kA with a frequency above 1 kHz. The paper investigates the effect of modifying the basic IDD power supply circuit by adding semiconductor diodes to shape the current pulse and improve its performance. The authors also focused on exploring the impact of the connection quality and their length and the associated loss in drive force while proving that a circuit with a reverse diode on the IDD coil is most beneficial and that the effect of the circuit on the front of the current pulse can significantly slow down the drive. Full article

A modular soft actuator with snakeskin-inspired scales that generates an anisotropic friction force is designed and evaluated in this study. The actuator makes it possible to fabricate soft robots that can move on various surfaces in the natural environment. For existing modulus soft robots, additional connectors and several independent pneumatic pumps are required. However, we designed precise connection and snake-scale structures integrated with a single pneumatic modular actuator unit. The precise structure was printed using a DLP 3D printer. The movement characteristics of the soft robot changed according to the angle of the scale structure, and the movement distance increased as the number of modular soft actuator units increased. Soft robots that can move in operating environments such as flat land, tubes, inclined paths, and water have been realized. Furthermore, soft robots with modularization strategies can easily add modular units. We demonstrate the ability to deliver objects 2.5 times heavier than the full weight of the soft robot by adding tong-like structure to the soft robot. The development of a soft robot inspired by snakeskin suggests an easy approach to soft robots that enables various tasks even in environments where existing robots have limited activity. Full article

The magnetic levitation reaction flywheel (MLRW) is a novel actuator of spacecraft attitude control because of its significant advantages, including lack of friction and active suppression of vibration. However, in a vacuum environment, the poor heat dissipation conditions make it more sensitive to various losses and rises in temperature. Therefore, increasing temperature is the key issue for components used in space. In this study, the losses of the three kinds of heat-generating areas in the MLRW, namely, the passive magnetic bearing (PMB), the active magnetic bearing (AMB) and brushless DC motor (BLDCM), were analyzed and calculated. Based on the electromagnetic field theory, the loss model of PMB was proposed. Based on the finite element method (FEM) and Bertotti model, the loss power of the AMB and the BLDCM was obtained. The calculated loss values were brought into the FEM to calculate the temperature field distribution of the MLRW system. Then, the key factors affecting the heat dissipation of the flywheel were obtained by combining thermal network analysis with the temperature field distribution. Finally, a prototype was fabricated. The maximum estimated and experimental temperatures were 34.8 °C and 36.8 °C, respectively, both at the BLDCM stator. The maximum error was 5.4%, which validates the calculated model. Full article

A micro-Coriolis mass flow sensor is a resonating device that measures small mass flows of fluid. A large vibration amplitude is desired as the Coriolis forces due to mass flow and, accordingly, the signal-to-noise ratio, are directly proportional to the vibration amplitude. Therefore, it is important to maximize the quality factor Q so that a large vibration amplitude can be achieved without requiring high actuation voltages and high power consumption. This paper presents an investigation of the Q factor of different devices in different resonant modes. Q factors were measured both at atmospheric pressure and in vacuum. The measurement results are compared with theoretical predictions. In the atmospheric environment, the Q factor increases when the resonance frequency increases. When reducing the pressure from 1 bar to $0.1$ bar, the Q factor almost doubles. At even lower pressures, the Q factor is inversely proportional to the pressure until intrinsic effects start to dominate, resulting in a maximum Q factor of approximately 7200. Full article

Monoclinic-phase VO₂ (VO₂(M)) has been extensively studied for use in energy-saving smart windows owing to its reversible insulator–metal transition property. At the critical temperature (T_c = 68 °C), the insulating VO₂(M) (space group P21/c) is transformed into metallic rutile VO₂ (VO₂(R) space group P42/mnm). VO₂(M) exhibits high transmittance in the near-infrared (NIR) wavelength; however, the NIR transmittance decreases significantly after phase transition into VO₂(R) at a higher T_c, which obstructs the infrared radiation in the solar spectrum and aids in managing the indoor temperature without requiring an external power supply. Recently, the fabrication of flexible thermochromic VO₂(M) thin films has also attracted considerable attention. These flexible films exhibit considerable potential for practical applications because they can be promptly applied to windows in existing buildings and easily integrated into curved surfaces, such as windshields and other automotive windows. Furthermore, flexible VO₂(M) thin films fabricated on microscales are potentially applicable in optical actuators and switches. However, most of the existing fabrication methods of phase-pure VO₂(M) thin films involve chamber-based deposition, which typically require a high-temperature deposition or calcination process. In this case, flexible polymer substrates cannot be used owing to the low-thermal-resistance condition in the process, which limits the utilization of flexible smart windows in several emerging applications. In this review, we focus on recent advances in the fabrication methods of flexible thermochromic VO₂(M) thin films using vacuum deposition methods and solution-based processes and discuss the optical properties of these flexible VO₂(M) thin films for potential applications in energy-saving smart windows and several other emerging technologies. Full article

The majority of soft pneumatic actuators for rehabilitation exercises have been designed for adult users. Specifically, there is a paucity of soft rehabilitative devices designed for infants with upper and lower limb motor disabilities. We present a low-profile vacuum-powered artificial muscle (LP-VPAM) with dimensions suitable for infants. The actuator produced a maximum force of 26 N at vacuum pressures of −40 kPa. When implemented in an experimental model of an infant leg in an antagonistic-agonist configuration to measure resultant knee flexion, the actuator generated knee flexion angles of 43° and 61° in the prone and side-lying position, respectively. Full article

In this work, thrust measurements of the high efficient and reliable vacuum arc thruster (HERVAT) are performed for different pulse energies. The thruster system includes a thruster head together with a newly developed pulse processing unit (PPU). The complete system (HERVAT + PPU) is able to perform more than 1 × 10⁷ pulses. Moreover, the influence of an integrated active magnetic nozzle is investigated. As a result, the thrust to power ratio, the average thrust level and the impulse bit for each configuration are measured and calculated. For the thrust measurements, a highly sensitive horizontal thrust balance with an active force actuator is used and operated in the thrust compensation mode. The investigated system is able to achieve levels from 5 to 40 μN and thrust to power ratios from 1 to 2 μN/W. The experimental results are compared to the data available in literature. Full article

Breath analysis is a powerful technique for detection of respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD). Nitric oxide (NO), nitrous oxide (N₂O), carbon dioxide (CO₂) and carbon monoxide (CO) present in breath sample acts a marker for respiratory disease. A system is proposed to design a Breath Analyser instrument. Its subsystems consist of a compact fast response laser system for analysis of multiple gases by infrared absorption. For quantitative analysis of trace gases in human breath, patient’s breath sample is collected inside a gas chamber. Two ends of gas chamber are mounted with concave mirrors with special type of mirror holders which have two angle adjustment piezo actuators. Angle adjustment piezo actuators are used to compensate for any angular misalignment in order of micro radians. Third piezo actuator is used for expansion of laser resonator. Special mirror holder consists of three plates which are supported with guide pins. Mirror is mounted on tilt plate which can be rotated in vertical and horizontal direction with the help of two piezo actuators. This mirror holder structure is made of stainless steel and can be used in any type of air and vacuum environment. It is found that for linear misalignment given to any mirror of optical cavity, the angular misalignment exists and vice versa. Thus artifact elimination of laser cavity is sensitive process. With three piezo actuator based special mirror holders, a precise measurement of laser absorption can be done. Full article

We consider piezoelectric flow energy harvesting in an internal flow environment with the ultimate goal powering systems such as sensors in deep oil well applications. Fluid motion is coupled to structural vibration via a cantilever beam placed in a converging-diverging flow channel. Two designs were considered for the electromechanical coupling: first; the cantilever itself is a piezoelectric bimorph; second; the cantilever is mounted on a pair of flextensional actuators. We experimentally investigated varying the geometry of the flow passage and the flow rate. Experimental results revealed that the power generated from both designs was similar; producing as much as 20 mW at a flow rate of 20 L/min. The bimorph designs were prone to failure at the extremes of flow rates tested. Finite element analysis (FEA) showed fatigue failure was imminent due to stress concentrations near the bimorph’s clamped region; and that robustness could be improved with a stepped-joint mounting design. A similar FEA model showed the flextensional-based harvester had a resonant frequency of around 375 Hz and an electromechanical coupling of 0.23 between the cantilever and flextensional actuators in a vacuum. These values; along with the power levels demonstrated; are significant steps toward building a system design that can eventually deliver power in the Watts range to devices down within a well. Full article

This paper reports on design, fabrication and characterization of high-Q MEMS resonators to be used in optical applications like laser displays and LIDAR range sensors. Stacked vertical comb drives for electrostatic actuation of single-axis scanners and biaxial MEMS mirrors were realized in a dual layer polysilicon SOI process. High Q-factors up to 145,000 have been achieved applying wafer level vacuum packaging technology including deposition of titanium thin film getters. The effective reduction of gas damping allows the MEMS actuator to achieve large amplitudes at high oscillation frequencies while driving voltage and power consumption can be minimized. Exemplarily shown is a micro scanner that achieves a total optical scan angle of 86 degrees at a resonant frequency of 30.8 kHz, which fulfills the requirements for HD720 resolution. Furthermore, results of a new wafer based glass-forming technology for fabrication of three dimensionally shaped glass lids with tilted optical windows are presented. Full article

High force, large displacement and low voltage consumption are a primary concern for microgyroscopes. The chevron-shaped thermal actuators are unique in terms of high force generation combined with the large displacements at a low operating voltage in comparison with traditional electrostatic actuators. A Nickel based 3-DoF micromachined gyroscope comprising 2-DoF drive mode and 1-DoF sense mode oscillator utilizing the chevron-shaped thermal actuators is presented here. Analytical derivations and finite element simulations are carried out to predict the performance of the proposed device using the thermo-physical properties of electroplated nickel. The device sensitivity is improved by utilizing the dynamical amplification of the oscillation in 2-DoF drive mode using an active-passive mass configuration. A comprehensive theoretical description, dynamics and mechanical design considerations of the proposed gyroscopes model are discussed in detail. Parametric optimization of gyroscope, its prototype modeling and fabrication using MetalMUMPs has also been investigated. Dynamic transient simulation results predicted that the sense mass of the proposed device achieved a drive displacement of 4.1µm when a sinusoidal voltage of 0.5V is applied at 1.77 kHz exhibiting a mechanical sensitivity of 1.7μm /^o/s in vacuum. The wide bandwidth frequency response of the 2-DoF drive mode oscillator consists of two resonant peaks and a flat region of 2.11 kHz between the peaks defining the operational frequency region. The sense mode resonant frequency can lie anywhere within this region and therefore the amplitude of the response is insensitive to structural parameter variations, enhancing device robustness against such variations. The proposed device has a size of 2.2 x 2.6 mm², almost one third in comparison with existing M-DoF vibratory gyroscope with an estimated power consumption of 0.26 Watts. These predicted results illustrate that the chevron-shaped thermal actuator has a large voltage-stroke ratio shifting the paradigm in MEMS gyroscope design from the traditional interdigitated comb drive electrostatic actuator. These actuators have low damping compared to electrostatic comb drive actuators which may result in high quality factor microgyroscopes operating at atmospheric pressure. Full article