Micro and Nano Engineering最新文献

Generally speaking, energy harvesting is an up-to-date technology that describes the possibility of capturing small amounts of energy (thermal, solar, or mechanical) from the surroundings and storing them as electrical energy for later uses when needed. Among the energy harvesting systems, the use of piezoelectric thin films and coatings is gaining increasing interest from both the academic and industrial communities, as these systems allow for the design and development of micro- and nano-scale devices, thanks to the possibility of being micromachined and to the added functionality offered by the electromechanical coupling. These peculiarities justify their use for different applications, ranging from high energy density harvesters to high sensitivity sensors, and even low power consumption and large displacement actuators. Further, the current focus of the research on piezoelectric energy harvesting coatings is shifting from fully inorganic to hybrid organic-inorganic (i.e., composite) systems, as the latter can offer higher flexibility (i.e., lower stiffness), making them more sensitive to small vibrations and therefore suitable for these specific harvesting conditions. In this regard, photoinduced polymerization (the so-called “UV-curing”) has become a suitable and reliable technique for the manufacturing of piezoelectric composite systems, as it is a solvent-free approach that allows for transforming a liquid mixture of monomers/oligomers into a solid 3D network in a few seconds, with a very limited energy consumption and a very high conversion. Besides, as the UV-curing process is very fast, the dispersed ceramic piezoelectric phase is not prone to settle down in the liquid resin, hence ensuring its homogeneous distribution within the polymer network after curing and better piezoelectric performance. The present review aims to provide the reader with an up-to-date overview of UV-curable coatings for piezoelectric energy harvesting purposes, highlighting their potential and piezoelectric features; further, some perspectives about possible future developments will be proposed.

In this paper the characterization of the mr-EBL 6000.5, which is an epoxy resin based chemically amplified negative tone resist from micro resist technology (Germany, Berlin) for an Intra-Level Mix & Match (ILM&M) approach is presented. The ILM&M approach combined at least two exposure technologies on the same resist layer showing the advantage to resolve patterns of different dimensions with less process steps and short processing time. Since the mr-EBL 6000.5 resist is capable of being sensitive to both electron- and UV-radiation, process parameters for i-line stepper lithography and electron beam lithography (EBL) needs to be investigated to be capable for the ILM&M approach. First, a spin curve and a post exposure bake (PEB) study were applied to find suitable process parameters for both exposure technologies. Furthermore, the minimum feature sizes for both patterning technologies are investigated by using a 500 nm thick resist layer. The impact of small feature sizes near the CD-limit of the used i-line stepper (350 nm) on the resist thickness after the development was investigated in dependence of the PEB. After all parameters were examined, they were combined to be used in the ILM&M.

This article discusses the important role that optical lithography has played in realizing Moore's Law. With the introduction of Artificial Intelligence, Machine Learning, and the Internet of Things, the demand for computing power and data storage capacity has never been as large as today. Optical lithography has been able to keep up with the resolution demand by increasing the Numerical Aperture of the projection Lens, decreasing the wavelength and innovative resist schemes. After the introduction of Immersion lithography and Double patterning, EUV was introduced by the industry. Although the transition from 193 nm lithography to EUV lithography was very difficult, EUV follows the same scaling laws as Optical Lithography. The conclusion is that the scaling laws of Optical Lithography continue to support Moore's Law, through the development of high NA EUV Lithography.

In this study, a method for depositing and patterning the thermosensitive polymer poly(N-isopropylacrylamide) on SiO₂ surfaces is presented for potential use in nano-sized microfluidic channels. Two approaches based on nanolithographic processes are shown for this purpose. In both cases, a self-assembling monolayer consisting of (3-aminopropyl)-dimethylethoxysilane was bound to the hydroxyl group of the substrate surface and subsequently functionalized with the polymerization initiator α-bromoisobutyryl bromide. In the first approach the silane monolayer itself was patterned using a photoresist and a lift-off process, followed by the selective deposition of the initiator, which starts a substrate-induced atom transfer radical polymerization for the growth of polymer on the silane monolayer. In the second approach, the lift-off takes place after the polymerization on the substrate surface. The result of this study shows the successful application of the process steps for the nano-dimensioned grafting of poly(N-isopropylacrylamide) onto SiO₂ substrates. The reaction time of the silane monolayer with the polymerization initiator and the composition of the reaction solution used were found to have the greatest influence of the processes. AFM and XPS analysis of the functionalized surfaces revealed patterned growth of both the self-assembling monolayer and the polymer structures.

Over the past few years, water quality monitoring has swiftly emerged as a thrust area for most of the developing nations. Despite its renewable essence, incessant industrialization and urbanization have depleted the natural water resources, culminating in adverse impact on potable water quality. As a consequence, reliable technologies with utmost sensitivity and accurate predictions vis-à-vis authentic qualitative standards are urgently needed. Herein, interest in using gold nanoparticles (Au NPs) biosensors to gauge the qualitative profile of water resources has been quite significant. Major fascinations for Au NPs biosensing driven water quality monitoring are steadfast preparation methodologies, well-understood mechanisms for size-shape modulation and inert sensitivity manifested remarkable functionalization abilities. The size-shape modulated functionalization advances for Au NPs are the dynamic outcomes of their quantum effects, anchored via single or multidimensional quantum confinements (QCs). Morphologies as vibrant as rod, spherical, cylindrical, shells and combinatorial regime have been the backbone aspects of Au NPs based biosensors. With such insights, the present article focuses on last decade noted advances aimed at Au NPs biosensors assessed water quality. The studies discussed herewith were retrieved from Pubmed using the keywords, “Gold Nanoparticle Biosensors for Water Quality Monitoring”. The knowledge shared herein could consolidate the fabrication of future Au nanomaterials based sensing technologies vis-à-vis functionalization mechanisms, cost considerations, precision aspects, integrated possibilities and long-term cautions.

Plasmonic metamaterial absorbers (PMAs) designed for multispectral imaging in the infrared (IR) with uncooled microbolometers are investigated. The study presents Fourier transform infrared spectroscopy (FTIR) measurements of PMAs consisting of metal-insulator-metal-stacks (MIM) with square-shaped micropatches as top metal layers. The measurements reveal high absorptances of 82% to 99% for distinct wavelengths within a range from 2 μm to 9.2 μm. The spectra are evaluated with respect to the lateral dimensions of the patches and to the refractive indices of the used dielectrics SiO₂, Al₂O₃ and Ta₂O₅. Numerical simulations and analytical calculations of the TM₀₁₀-mode using the transmission line model (TLM) for microstrip antennas show good qualitative agreement with the measurement results. Additionally, bispectral PMAs were fabricated consisting of fields of PMAs with two different patch sizes arranged in a chessboard pattern. The individual fields of this pattern correspond to microbolometers with 12 μm pitch in shape and size. Two distinct absorption maxima can be seen in the spectra measured by FTIR. The choice of materials, deposition methods and patterning processes is suitable for the integration into the existing Fraunhofer IMS's nanotube microbolometer technology to realize multispectral infrared imaging. The fabrication process is CMOS-compatible and carried out on 8-in. wafers.

Zinc oxide (ZnO) has emerged as one of the most promising candidates for mass-producing cost-efficient optoelectronic devices. This is primarily because it can be synthesized in high-quality nanostructures on a wide range of substrates through relatively simple chemical methods. However, producing p-type ZnO, regardless of the chosen method, remains an open and controversial issue. In this work, Li-doped ZnO nanostructures of varying Li-cocnentration were produced via a two-step hydrothermal growth synthesis and an in-depth analysis based on with Field Emission Scanning Electron Microscopy (FE-SEM), X-ray diffraction (XRD), Raman Spectroscopy, Extended X-Ray Absorption Fine Structure (EXAFS) Spectroscopy, and temperature-dependent Photoluminescence (PL) was carried out in an effort to gain insights into the Li-incorporation mechanisms. The findings indicated a strong interplay between the native defects responsible for the inherent n-type character of the material and Li incorporation. It is suggested that this interplay hinders the successful conversion of the Li-doped nanorods into p-type nanostructures and that when employing the hydrothermal approach it is essential to identify the precise conditions necessary for genuine Li incorporation as a Zn substitutional.

We present a novel fabrication approach to an integrated nanophotonic platform, based on a III-V membrane bonded to a Si substrate with benzocyclobutene (BCB). The process incorporates a hybrid lithography strategy combining deep-UV and electron-beam lithography on the same wafer. We report for the first time the usage of deep-UV scanner lithography for the fabrication of the active-passive tapers and sub-micron waveguides on the same wafer, which enables better critical dimension control, uniformity, and reproducibility. The platform uses an active-passive butt-joint interface and includes components such as distributed feedback (DFB) and distributed Bragg reflector (DBR) lasers, electro-optical (EO) and electro-absorption (EA) modulators, and sub-micron ultra-confined passive waveguides, all monolithically integrated into a single membrane layer. The active devices have a heat sink achieved by ultra-thin BCB bonding. Lasers demonstrate up to 26 mW of optical power in the waveguide and a direct modulation bandwidth of up to 21 GHz. The modulators show static extinction up to 28.8 dB.

Gold is a promising material for movable components in MEMS devices by the high mass density, which allows reduction of the Brownian noise. Mechanical properties of metallic materials are known to be affected by the sample size effect. When bending test is utilized, the sample geometry effect is another factor. In this study, effects of the shape of the cross-section, or the cross-sectional geometry effect, are evaluated using micro-cantilevers with a trapezoidal cross-section. The yield stresses are ranged from 112 MPa to 185 MPa in micro-cantilevers composed of single crystalline gold, and the yield stresses varied from 372 MPa to 489 MPa in polycrystalline gold micro-cantilevers. The yield stress is found to be higher in the micro-cantilever having a smaller ratio of the top width over the bottom width, which demonstrates the cross-sectional geometry effect. Also, the cross-sectional geometry effect is more significant in the polycrystalline micro-cantilevers.

Maskless UV photolithography is increasingly used, especially in research environments where low turn-around time for new designs improves productivity. Here, we fabricate pyrolytic carbon interdigitated microelectrodes with small interelectrode gaps, good adhesion to the carrier substrate, high surface area and excellent electrochemical properties using maskless UV photolithography with two negative epoxy-based photoresists, namely the commonly used SU-8 and the recently developed mr-DWL. The minimum realizable trench width in 15 μm thick photoresist films is 2.4 ± 0.15 μm for mr-DWL 5 and 3.1 ± 0.10 μm for SU-8 2035. After pyrolysis, the two resulting pyrolytic carbon materials show similar electrochemical properties. However, shrinkage during pyrolysis is significantly lower for mr-DWL compared to SU-8, which is beneficial for the fabrication of interdigitated microelectrodes. Furthermore, delamination of the electrodes during processing and operation is prevented due to the introduction of poly silicon adhesion structures. This work provides valuable insights into maskless UV lithography as well as into the pyrolytic carbon process to increase the yield, performance and productivity for fabrication of microelectrodes.