We report on the development of a process chain for the conformal surface-structuring at sub-microscale of complex parts. More especially, the main objective was to manufacture functional microparts ...with engineered sidewall topographies. The solution proposed is based on the surface structuring of the sidewalls of resin molds used in the LIGA process (Lithography Galvanik Abformung). The surface structuring was achieved by depositing sub-micrometer particles prior to electroforming step. The length scale of the structures produced was controlled by the size of the particles deposited. The particle deposition process was monitored by using a quartz crystal microbalance and optimized on flat surfaces. It was successfully applied to produce structured nickel phosphorus LIGA parts. The structured surfaces produced were also used to create liquid infused surfaces, having low wetting hysteresis.
Display omitted
En la presente conversación Abel Perles revisa la conformación, el devenir y la transformación exponencial de PRODUCTORA desde sus inicios en 2006, a partir de eventos relevantes para el estudio, así ...como también su carácter cosmopolita y el saberse actores emergentes de una nueva generación de arquitectos. La participación en convocatorias internacionales y el temprano e inmediato reconocimiento a la calidad de sus trabajos, que le posibilitó la invitación a concursos de arquitectura y la realización de grandes obras en y fuera de México son asimismo temas de este intercambio. El sentido del nombre de la oficina y las inquietudes proyectuales, conceptuales, formales y materiales vinculadas a la producción de obras, junto a un fuerte interés por difundir y promocionar la arquitectura y las discusiones que acontecen en y desde América Latina, forman parte de esta conversación. De igual forma, está presente una reflexión en torno a PRODUCTORA, en tanto un nombre que anticipa un modo de hacer latinoamericano que se sucede entre lo obvio, lo inteligente, lo necesario, las incomodidades, la informalidad y la incertidumbre.
Deep X-ray Lithography (DXRL) has conventionally processed shapes that depend on the two-dimensional pattern of the X-ray mask used. In this study, we attempted to fabricate microstructures of ...micron-order 3D arbitrary shapes on a PMMA surface by using a high-precision multi-step exposure system with a 2-axis PZT actuators. The sample on the PZT actuator stages controlled was exposed, and a micro conical shape with a bottom diameter of 63 µm, a top diameter of 2 µm, and a height of about 70 µm was successfully fabricated. This was in accordance with the designed model and we could control micron-order processing.
We fabricated sectoral-pillar structures for Dihedral Corner Reflector Array (DCRA) using Deep X-ray Lithography (DXRL) in New SUBARU Synchrotron Radiation Facility. We studied process conditions ...such as a start timing of development after exposure and development temperature. We succeeded in fabricating a structure without of micro-cracks on sidewalls of the pillar and in demonstration of floating image using the fabricated DCRA.
The distinctive crystal characteristics of undoped LiGa5O8 allow the production of abundant defects and traps in the structure, contributing to attractive luminescent properties. In this work, the ...mechanoluminescent pathways of LiGa5O8 are demonstrated in terms of the defect induced localized energy levels and trap levels, which are further optimized by adjusting the synthesis atmosphere. The results suggest that the LiGa5O8 synthesized under a reducing atmosphere exhibits an extremely intense mechanoluminescence, which is even better than that of commercial ZnS:Cu. Because of the existence of shallow trap with the spontaneous transfer activity at room temperature, the mechanoluminescence of LiGa5O8 can also exhibit a persistent behavior, overcoming the transient emitting problem in most of the previous mechanoluminescent materials. In addition, the mechanoluminescence of LiGa5O8 can be easily and quickly recovered by refilling the energy in traps. As a result, the undoped LiGa5O8 is confirmed to be an efficient material with intense, persistent, and recoverable mechanoluminescence, which is promising to substitute the doped ones for various applications.
The mechanoluminescent pathways of LiGa5O8 are demonstrated in terms of the defect induced localized energy levels and trap levels. After optimization by the reaction atmosphere, the undoped LiGa5O8 exhibits extremely intense mechanoluminescence with persistent and recoverable behaviors, which is expected to substitute the doped ones for various applications.
LiGa5O8 ceramics with inverse spinel structure were prepared in a temperature range of 1200–1300 ℃ by solid-state reaction method. LiGa5O8 ceramics crystallized in cubic structure with space group ...P4332, in which Li+ and Ga3+ distributed in the octahedral B sites with 1:3 ordering. The optimal microwave dielectric properties with εr =10.51, Q × f = 127,040 GHz, and τf = –60.16 ppm/℃ were achieved at 1260 ℃ for 6 h. Microwave dielectric properties were discussed in combination with the intrinsic characteristics of crystal structure by packing fraction, Raman spectra, and infrared reflectivity spectrum. Additionally, CaTiO3 was used to suppress τf of LiGa5O8 ceramics to near zero, and optimized performances of εr = 12.79, Q × f = 109,752 GHz and τf = +4.07 ppm/℃ were obtained for 0.94LiGa5O8‐0.06CaTiO3 ceramics at 1260 ℃. These bright spots make LiGa5O8 ceramic a potential candidate for 5 G and millimeter wave technology.
Display omitted
•A triboelectric energy harvester design scaled down to MEMS size.•Structurally optimized for maximum average power and power density.•High operating frequency (1.15 kHz) and wide ...operating bandwidth (920 Hz).•Output average power 0.179 μW, peak power 0.597 μW and power density 2.64 mWcm−3.•Acceleration normalized power density 30.3 μWcm−3/g2 and sensitivity 43 mV/g
A novel triboelectric energy harvesting (TEH) and sensing system scaled down to microelectromechanical systems (MEMS) size is presented. The design is structurally optimized for harvesting the highest average power and power density while ensuring the structural robustness. Unlike traditional triboelectric energy harvesters, this design results in a high operating frequency with a wide bandwidth. Adoption of MEMS fabrication techniques including the use of spin-coated Teflon AF rather than a Teflon sheet, adaptation of UV-LIGA (Ultra-Violet Lithographie, Galvanoformung, Abformung) with modifications and implementation of a thick polyimide sacrificial layer make the fabrication process unique. If excited by ±9.33 g external vibration with a frequency of 1.15 kHz, the TEH can generate 0.179 μW average power and 0.597 μW peak power at an optimum resistive load of 256 kΩ. The peak surface power density, volumetric power density and acceleration-normalized volumetric power density reach 3.98 μWcm−2, 2.64 mWcm-3 and 30.3 μWcm-3/g2, respectively. While the surface power density of the presented TEH is moderate, the volumetric power density and acceleration-normalized volumetric power density are quite competitive among the state-of-the-art designs. The TEH also demonstrates a wide operating frequency bandwidth of 920 Hz. If operated as an accelerometer, the device shows a linear sensitivity of 43 mV/g. Although the simulation predicts the optimum operating frequency and load resistance of the system to be at 800 Hz and 10 MΩ, respectively, the experimental results demonstrate these values to be at 1150 Hz and 256 KΩ. A few fabrication anomalies, most notably the notching in the Teflon layer and bowing of the proof-mass, are responsible for this deviation. In addition, a distortion is observed in the simulated output voltage profile which is not present in the experimental output voltage profile due to the presence of the parasitic capacitance in the experimental circuit. The aforementioned triboelectric energy harvester can have specific applications in the sensor and actuator systems in the aircraft industry as well as in the automobile industry, micro-robotic systems, prosthetic systems, and sensor nodes in the internet of things (IoT) due to its operating frequency and bandwidth range.
•Conformal z-axis accelerometer fabricated on flexible polyimide substrate.•Double layer UV-LIGA process deployed for increased sensitivity as high as 187 fF/g.•Bendability up to 2cm radius of ...curvature without performance degradation.•Resonant frequency varying between 800Hz and 1100Hz.
Surface micro-machined z-axis capacitive accelerometers were designed and fabricated on a flexible polyimide substrate, conformal down to 2cm radius of curvature with the stresses sustained by all layers well below the yield strength for each material. A novel UV-LIGA fabrication technique was developed to realize a thicker proof-mass (8μm) compared to the spring (3μm), thus decoupling the two important parameters: the stiffness and the proof-mass to achieve higher sensitivity. Devices with three different sizes were fabricated with the capability of sustaining under distinct amount of acceleration and tuned to frequencies ranging from 600Hz to 1100Hz. The largest device, having the area of 960μm×960μm, showed a sensitivity of 187 fF/g with a SNR (Signal to Noise Ratio) of at least 100 when characterized at its resonance frequency of 800Hz. The applied acceleration was ±4g in addition to gravitation.
Currently, most of the mechanoluminescence (ML) phosphors strongly depend on postirradiation stimulation using ultraviolet light (denoted as “UV exposure” from hereon) to show the ML. However, only a ...few transition metal cations are proven to be effective luminescence centers, which hinder the development of more ML phosphors. This study reports a self‐recoverable deep‐red‐to‐near‐infrared ML using Cr3+‐doped LiGa5O8 phosphor with fully recoverable ML performance. The ML performance can be further optimized by tuning the trap redistributions by codoping the phosphor with Al3+ and Cr3+ cations. Theoretical calculations reveal the important role of Cr dopants in the modulation of local electronic environments for achieving the ML. Owing to the induced interelectronic levels and shallow electron trap distributions, the electron recombination efficiency is enhanced both through direct tunneling and energy transfer toward the dopant levels. Moreover, the ML of Cr3+‐doped LiGa5O8 can penetrate a 2‐mm‐thick pork slice, showing that it can have wide‐ranging in vivo applications, including the optical imaging of intracorporal stress/strain distribution and dynamics. Therefore, this work fabricates a novel ML material with self‐recoverable luminescence in an extended wavelength range, increasing the number of potential ML candidates and promoting the fundamental understanding and practical applications of ML materials.
Self‐recoverable mechanoluminescence (ML) in Cr3+‐doped LiGa5O8, which overcomes the dependence on UV exposure stimulation, is shown. This ML phosphor realizes a fully reversible ML intensity, which relies on the electronic levels and shallow electron trap distributions. This study provides a novel ML material system for future development in broad bioapplications.
In order to solve the problem that the low-g omnidirectional MEMS inertial switches cannot recognize the load direction, a nickel omnidirectional MEMS inertial switch with identifiable load direction ...and uniform in-plane threshold distribution was designed. The switch is mainly composed of a spring–mass system, four independent flexible radial electrodes and an axial electrode. The function of identifying the direction of acceleration is realized by detecting the closed states of different electrodes. According to the design results of MEMS inertial switch, the dynamic performance of the switch was analyzed by ANSYS software. The results show that the designed switch meets the functional requirements of load direction identification. Based on UV-LIGA multilayer photolithography, the nickel MEMS inertial switch was fabricated on a steel substrate. In the process of fabrication, the line width compensation method was used to reduce the dimensional error caused by swelling phenomenon and removal process of the photoresist. What's more, the thickness compensation method was used to reduce the process error caused by flattening treatment. The overall dimension of the switch is 5300 × 5300 × 270 μm and the smallest line-width is 20 μm. Ultimately, the fabricated switch was tested by the centrifuge device and dropping hammer in XOY plane and Z-axis direction. The dynamic threshold of the switch is between 7.9 and 11.3 g, and the response time in each direction is less than 2 ms. The switch can recognize the direction of acceleration in XOY plane and Z-axis. The switch has an excellent anti-overload performance.
Display omitted
•A low-g MEMS inertial switch with identifiable load direction was designed.•The function was realized by detecting the closed states of different electrodes.•The switch achieves uniform threshold acceleration in each sensitive direction.•The line width compensation method was proposed to improve fabrication accuracy.•The switch was verified with the centrifugal device and the dropping hammer system.
PDF
