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In this work, we report a direct measurement of the forces exerted by a tubulin/kinesin active nematic gel as well as its complete rheological characterization, including the quantification of its shear viscosity, η, and its activity parameter, α. For this, we develop a method that allows us to rapidly photo-polymerize compliant elastic inclusions in the continuously remodeling active system. Moreover, we quantitatively settle longstanding theoretical predictions, such as a postulated relationship encoding the intrinsic time scale of the active nematic in terms of η and α. In parallel, we infer a value for the nematic elasticity constant, K, by combining our measurements with the theorized scaling of the active length scale. On top of the microrheology capabilities, we demonstrate strategies for defect encapsulation, quantification of defect mechanics, and defect interactions, enabled by the versatility of the microfabrication strategy that allows to combine elastic motifs of different shapes and stiffnesses that are fabricated in situ. [ABSTRACT FROM AUTHOR]

This article proposes a novel demonstration of a low-loss polymer channel hybridized with a titania core leading to a nano-waveguide elongated in the normal direction to the substrate. It is aimed at using the quasi-transverse magnetic (TM) mode as the predominant mode in compact photonic circuitry. A detailed design analysis shows how a thin layer of a higher-refractive index material in a trench within the core of the waveguide can increase the confinement and reduce the propagation losses. This thin layer, produced by atomic layer deposition, covers the entire polymer structure in a conformal manner, ensuring both a reduction of the surface roughness and a stronger field confinement. The trench can be made at any place within the polymer channel and therefore its position can be tuned to obtain asymmetric modal distribution. The waveguide is demonstrated at telecom wavelengths, although the material's properties enable operation over a large part of the electromagnetic spectrum. We measured propagation losses as low as 1.75 ± 0.32 dB/cm in a 200 nm × 900 nm section of the waveguide core. All processes being mass-production compatible, this study opens a path towards easier integrated-component manufacture. [ABSTRACT FROM AUTHOR]

In order to promote the bubble removal in the fabrication process of micro structure and enhance nickel micro electroforming, megasonic field was introduced in this paper. Electrochemical measurement was used to analyze the effects of megasonic on micro electroforming, including tests on curves of cycle voltammetry, linear sweep voltammetry, Tafel and electrochemical impedance spectroscopy. Enhancement mechanism of megasonic field on bubble removal in nickel micro electroforming was revealed and micro structures with different dimensions were fabricated. Results of electrochemical measurement demonstrated that megasonic filed not only can promote the sufficient contact between substrate and electroforming solution, but also can decrease solution resistance and increase current. Besides, megasonic field can promote nickel deposition and weaken hydrogen evolution, improving the current conversion efficiency. Fabrication results verified that megasonic field is beneficial to promote bubble removal from the surface of electroforming area. Less surface defects, higher processing efficiency and higher success rate of micro structures fabrication can be accomplished under 6 W cm−2 megasonic field. This study may provide novel idea and method on fabrication of micro-nano structure. [Display omitted] [ABSTRACT FROM AUTHOR]

Micro fabrication of tapered glass capillaries with on-demand geometry is one of the essential issues to make specific devices for electrophysiological experiments, microfluidics, pharmaceutics. Capitalizing on chemical etching and mechanical polishing, we have developed a reliable microfabrication method to make tapered glass capillaries with on-demand size. The tip ending diameter reaches from several microns to hundreds of microns within one hour fabrication time, which can meet the requirement for microfabrication of microfluidic devices. To demonstrate the performance of the hybrid microfabrication method, the effect of etching time, and etchant concentrations are proposed. Furthermore, the surface quality of fabricated device is demonstrated to show the advantages of our microfabrication method. Then two typical applications such as the soft manipulation of zebrafish embryo and the production of emulsion droplets are performed. This hybrid microfabrication method of chemical etching combined with mechanical polishing shows great advantages to obtain on-demand size of tapered glass capillaries, and these features make it highly promising for microfabrication of glass capillary devices. [2021-0229] [ABSTRACT FROM AUTHOR]

Stereolithography is emerging as a promising additive manufacturing technology for a range of applications in the medical domain. However, for miniature, medical devices such as those used in ophthalmic surgery, a number of production challenges arise due to the small size of the components. In this work, we investigate the challenges of creating sub-millimeter features for a miniature, functional trocar using Stereolithography. The trocar cannula system is used in eye surgery to facilitate a passage for other instruments. A standard trocar consists of a hollow cannula and a flexible check valve. The research was performed in two stages: in the first stage we investigated the effect of different materials and print settings on the current design of the cannula and the valve separately, and in the second stage we used these findings to optimize the design and production process. After the first investigation, it became apparent that even though the dimensions of the trocar are within the feature size range of Stereolithography, all hollow features tended to fuse shut during printing. This effect appeared regardless of the materials or print settings, and can be attributed to refraction of the laser source. In order to circumvent this, we identified two potential strategies: (1) increasing the negative space surrounding features; and (2) decreasing the surface area per layer. By applying these strategies, we tested a new design for the cannula and valve and managed to 3D print a functional trocar, which was tested in an artificial eye. The design of the 3D printed trocar allows for further personalization depending on the specific requirements of both patient and surgeon. The proposed strategies can be applied to different applications to create miniature features using Stereolithography.

This article proposes a novel demonstration of a low-loss polymer channel hybridized with a titania core leading to a nano-waveguide elongated in the normal direction to the substrate. It is aimed at using the quasi-transverse magnetic (TM) mode as the predominant mode in compact photonic circuitry. A detailed design analysis shows how a thin layer of a higher-refractive index material in a trench within the core of the waveguide can increase the confinement and reduce the propagation losses. This thin layer, produced by atomic layer deposition, covers the entire polymer structure in a conformal manner, ensuring both a reduction of the surface roughness and a stronger field confinement. The trench can be made at any place within the polymer channel and therefore its position can be tuned to obtain asymmetric modal distribution. The waveguide is demonstrated at telecom wavelengths, although the material’s properties enable operation over a large part of the electromagnetic spectrum. We measured propagation losses as low as 1.75 ± 0.32 dB/cm in a 200 nm × 900 nm section of the waveguide core. All processes being mass-production compatible, this study opens a path towards easier integrated-component manufacture.

We present a study of the natural (resonance) frequencies of a tunable in-plane Microelectromechanical portal frame (U-shape) under DC electrostatic loads. The structure is designed and fabricated to excite the in-plane anti-symmetric (sway, first) and the symmetric (second) modes. Experimental results show high tunability of the resonance frequencies of both modes due to the electrostatic forces. Finite element simulations show good agreement with the experimental measurements. Further simulations are presented for the tunability of the natural frequencies of other higher-order modes using various electrode configurations. Frequency-response curves are presented for pure AC actuation of the first two modes showing strong nonlinear softening behavior due to the geometric nonlinearities of the portal frame. [2020-0269] [ABSTRACT FROM AUTHOR]

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Miniaturization of parts is proceeding in various industrial applications such as medical, automotive electrical equipment and nanotechnology. Furthermore, lots of these parts have complex shapes which are difficult to fabricate by normal machining or forming. Selective Laser Melting (SLM) process is one of the techniques to improve this drawback, because SLM process can produce the complex shaped parts. However, commercial SLM machine tends to fabricate the large size products in recent years. Therefore, accuracy of its dimension is insufficient for the precision parts making. Precision SLM machine is expected to become an effective method for manufacturing small parts. In this research, we developed a precision SLM machine equipped with customized Computer Aided Manufacturing (CAM) software and single mode Yb fiber laser which can focus into 50 μm. Eventually, the precision parts fabricated by developed SLM machine have the wall with thickness of 100 μm. Various types of precision and complexed shape parts were fabricated by developed SLM machine. [ABSTRACT FROM AUTHOR]

The combination of extreme miniaturization with a high sensitivity and the potential to be integrated in an array form on a chip has made silicon-based photonic microring resonators a very attractive research topic. As biosensors are approaching the nanoscale, analyte mass transfer and bonding kinetics have been ascribed as crucial factors that limit their performance. One solution may be a system that applies dielectrophoretic forces, in addition to microfluidics, to overcome the diffusion limits of conventional biosensors. Dielectrophoresis, which involves the migration of polarized dielectric particles in a non-uniform alternating electric field, has previously been successfully applied to achieve a 1000-fold improved detection efficiency in nanopore sensing and may significantly increase the sensitivity in microring resonator biosensing. In the current work, we designed microring resonators with integrated electrodes next to the sensor surface that may be used to explore the effect of dielectrophoresis. The chip design, including two different electrode configurations, electric field gradient simulations, and the fabrication process flow of a dielectrohoresis-enhanced microring resonator-based sensor, is presented in this paper. Finite element method (FEM) simulations calculated for both electrode configurations revealed ∇E2 values above 1017 V2m−3 around the sensing areas. This is comparable to electric field gradients previously reported for successful interactions with larger molecules, such as proteins and antibodies.

A major challenge in studying tumor cell invasion into its surrounding tissue is to identify the contribution of individual factors in the tumor microenvironment (TME) to the process. One of the important elements of the TME is the fibrous extracellular matrix (ECM) which is known to influence cancer cell invasion, but exactly how remains unclear. Therefore, there is a need for new models to unravel mechanisms behind the tumor-ECM interaction. In this article, we present a new microfabrication method, called selective curing, to integrate ECM-mimicking layers between two microfluidic channels. This method enables us to study the effect of 3D matrices with controlled architecture, beyond the conventionally used hydrogels, on cancer invasion in a controlled environment. As a proof of principle, we have integrated two el e c trospun Polycaprolactone (PCL) matrices with different fiber diameters in one chip. We then studied the 3D migration of MDA-MB-231 breast cancer cells into the matrices under the influence of a chemotactic gradient. The results show that neither the invasion distance nor the general cell morphology is affected significantly by the difference in fiber size of these matrices. The cells however do produce longer and more protrusions in the matrix with smaller fiber size. This microfluidic system enables us to study the influence of other factors in the TME on cancer development as well as other biological applications as it provides a controlled compartmentalized environment compatible with cell culturing. [ABSTRACT FROM AUTHOR]

The precise mechanisms that lead to orthopedic implant failure are not well understood; it is believed that the micromechanical environment at the bone-implant interface regulates structural stability of an implant. In this work, we seek to understand how the 3D mechanical environment of an implant affects bone formation during early osteointegration. We employed two-photon lithography (TPL) direct laser writing to fabricate 3-dimensional rigid polymer scaffolds with tetrakaidecahedral periodic geometry, herewith referred to as nanolattices, whose strut dimensions were on the same order as osteoblasts’ focal adhesions (∼2 μm) and pore sizes on the order of cell size, ∼10 μm. Some of these nanolattices were subsequently coated with thin conformal layers of Ti or W, and a final outer layer of 18 nm-thick TiO 2 was deposited on all samples to ensure biocompatibility. Nanomechanical experiments on each type of nanolattice revealed the range of stiffnesses of 0.7–100 MPa. Osteoblast-like cells (SAOS-2) were seeded on each nanolattice, and their mechanosensitve response was explored by tracking mineral secretions and intracellular f-actin and vinculin concentrations after 2, 8 and 12 days of cell culture in mineralization media. Experiments revealed that the most compliant nanolattices had ∼20% more intracellular f-actin and ∼40% more Ca and P secreted onto them than the stiffer nanolattices, where such cellular response was virtually indistinguishable. We constructed a simple phenomenological model that appears to capture the observed relation between scaffold stiffness and f-actin concentration. This model predicts a range of optimal scaffold stiffnesses for maximum f-actin concentration, which appears to be directly correlated with osteoblast-driven mineral deposition. This work suggests that three-dimensional scaffolds with titania-coated surfaces may provide an optimal microenvironment for cell growth when their stiffness is similar to that of cartilage (∼0.5–3 MPa). These findings help provide a greater understanding of osteoblast mechanosensitivity and may have profound implications in developing more effective and safer bone prostheses. Statement of Significance Creating prostheses that lead to optimal bone remodeling has been a challenge for more than two decades because of a lack of thorough knowledge of cell behavior in three-dimensional (3D) environments. Literature has shown that 2D substrate stiffness plays a significant role in determining cell behavior, however, limitations in fabrication techniques and difficulties in characterizing cell-scaffold interactions have limited our understanding of how 3D scaffolds’ stiffness affects cell response. The present study shows that scaffold structural stiffness affects osteoblasts cellular response. Specifically this work shows that the cells grown on the most compliant nanolattices with a stiffness of 0.7 MPa expressed ∼20% higher concentration of intracellular f-actin and secreted ∼40% more Ca and P compared with all other nanolattices. This suggests that bone scaffolds with a stiffness close to that of cartilage may serve as optimal 3D scaffolds for new synthetic bone graft materials. [ABSTRACT FROM AUTHOR]

We propose the smallest preload generation mechanisms that provide force between the rotor and the one cubic millimeter stator in a micro ultrasonic motor. Miniaturizing the preload mechanism is key for implementation of a micro ultrasonic motor with the best performance into micro devices. In this paper, we evaluate two kinds of preloads that exert in the axial and radial directions: an axial preload mechanism and a radial preload mechanism. The experiments clarify how both preload mechanisms improve motor performance measures such as angular velocity, torque, and efficiency. The micro ultrasonic motors with both preload mechanisms generated torque over 10 μNm at the experimentally optimized preload of approximately 6 g. By designing the miniature preload mechanisms using a micro coil spring, the preload mechanisms are miniaturized with similar motor performance. At present, they represent the smallest and most powerful ultrasonic motors with preload mechanisms. [ABSTRACT FROM AUTHOR]

In the process of two photon polymerization, the focused beam should be perpendicular to the materials to be processed. But actually it is hard to control, because of the errors of the optical system and the three-dimensional motion platform. So, the inconsistencies of voxels in size and angle due to the errors mentioned above will seriously impact the surface quality of the products. In this paper, the size, angle and location of the titled voxels formed by inclined beam are simulated according to matrix optics and polymerization theory. According to the simulation results, a method for angle errors compensation with the aid of scanning galvanometer is proposed. Although the angle of the voxels can be controlled by scanning galvanometer, but the deflection angles of the scanning galvanometer have a certain range, it should be lower than 3°, or the deformation of the voxels will be serious. Therefore the consistency of the voxel in both size and angle will be ensured. [ABSTRACT FROM AUTHOR]

Microinjection moulding is a key enabling technology for replicating miniaturized components and parts with functional features at the micrometer and even sub-micrometer length scale. The micro moulding tools used in the process chain are critical for delivering high quality parts for the duration of the product life cycle, and recently tool coatings such as Diamond-like carbon (DLC) have been used to extend their use and enhance the performance. The micro injection moulding process has high injection speeds with cyclic heat transfer characteristics, and little is understood on how the localised heat transfer at the surface will influence the DLC surface coating delamination and cracking. In this research a microinjection moulding process using three different polymers, Polypropylene (PP), Acrylonitrile butadiene styrene (ABS) and Polyether ether ketone (PEEK) is studied. Finite element analysis (FEA) simulation is utilised to identify the process temperature factors that lead to tool thermal expansion and dimensional changes that directly impact the life cycle of the coating. The theoretical and FEA results show that the mould material and the two coatings experience a significantly different thermal expansion from each other. It has also been shown that at the micro scale heat loss at the tool surface is dominant, and the variation in heat has a significant influence on the different thermal expansion rates. In particular the DLC coated micro rib features are particularly susceptible to high variations in heat transfer. The research identifies areas of the tool surface that experience sudden heat variation across the part surface, and concludes that through process optimisation it is possible to reduce the potential for DLC coating delamination and cracking during service. [ABSTRACT FROM AUTHOR]

Recently, there are growing demands in manufacturing of net shape micro parts for wide range of applications due to the increasing interest in miniaturization. In this paper, the fabrication of tetragonal phase zirconia/alumina (YSZ/Al2O3) nanocomposite micro-parts with high quality is presented. The fabrication process is based on soft lithography and colloidal powder dispersion. Experimental results showed that by optimizing the soft lithography and the dispersion process, it was possible to produce high-resolution micro-parts with well dispersed alumina. The X-ray diffraction results had confirmed the important role of the alumina particles in eliminating the emergence of monoclinic phase while the microstructures reveal a pure tetragonal phase. In addition, the sintered YSZ/Al2O3 micro parts achieved micro hardness with 20% superior to the pure YSZ sintered micro-parts with the addition of 5% alumina.

Surface texturing is considered to be an effective means of enhancing the properties of a tribological contact not only in a normal uni-directional sliding condition but also in fretting under lubricated conditions. Well-regulated “micro dimples” were formed on a flat surface using the method of micro fabrication. In this study, a bearing steel (HV760) was used for the specimens with ball-on-flat configuration. The frictional force and relative movement between the specimens were measured simultaneously during fretting with a frequency 7.35 Hz, for fretting up to 2 × 105 cycles under a lubricated condition of 350 neutral oil (typically used for grease lubricated contacts). The normal load, and fretting stroke were varied in the range of 4.9 N to 22.1 N, 12 μm to 215 μm respectively. The initial running-in process (namely, the phenomenon of a significant reduction in the coefficient of friction seen in the early stages of fretting) was the main focus of the study, with comparisons being made between specimens with flat surfaces. The main findings were that a micro texturing surface resulted in a reduced number of cycles to complete the running-in process (when compared to the flat surface), but that the wear scar was wider in the micro texturing surface. It is proposed that the micro texturing surface provides a less stiff contact than the flat surface and that the lubricant can become entrapped in the dimples in the contact, and thus provide enhanced entrainment of the lubricant into the contact.

This paper reports a miniaturized piezoelectric accelerometer suitable for a small haptic actuator array. The accelerometer is made with zinc oxide (ZnO) nanowire (NW) grown on a copper wafer by a hydrothermal process. The size of the accelerometer is 1.5 × 1.5 mm2, thus fitting the 1.8 × 1.8 mm2 haptic actuator array cell. The detailed fabrication process of the miniaturized accelerometer is illustrated. Performance evaluation of the fabricated accelerometer is conducted by comparing it with a commercial piezoelectric accelerometer. The output current of the fabricated accelerometer increases linearly with the acceleration. The miniaturized ZnO NW accelerometer is feasible for acceleration measurement of small and lightweight devices. [ABSTRACT FROM AUTHOR]

Deep X-ray lithography with synchrotron radiation can be successfully used in fabrication of high-aspect-ratio microstructures (HARMs) micrometers up to several millimetres high. As such microstructures are often mechanically unstable, a supporting layer incorporated into a micropattern, was developed and studied. [ABSTRACT FROM AUTHOR]

Micro devices have been attracting attention accompanying industrial development in recent years. Higher-level microprocessing technique to produce them is demanded. The purpose of this study is to establish the novel technique to satisfy 3 functions: sub-μm process resolution, 3-dimensional flexibility and rapidity. This report proposed a nano-stereolithography method using evanescent light instead of propagating light in order to achieve the required functions. However, there are some important problems in exposing and curing process because of oxygen dissolved in photosensitive resin. Nitrogen purge was introduced to exposing unit to remove oxygen from the resin, which allowed us to solve the problem in exposing and curing process. [ABSTRACT FROM AUTHOR]

A technique using digital masks without ultraviolet light to rapidly print 3-D biopolymer structures with complex microarchitectures in a microfluidic chip has been demonstrated. In this approach, a customized system is used to project light images on a photoconductive substrate in order to create localized virtual electrodes when an alternating electric field is applied across the fluidic medium in an optically controlled digital electropolymerization chip. Upon these virtual electrodes, the localized electric fields are generated, which could activate the polymerization of acrylate-based molecules, such as poly(ethylene glycol) diacrylate (PEGDA), to form microstructures with the same shapes as the projected light images. We have demonstrated that the 3-D PEGDA microstructures with the customized shapes could be fabricated rapidly through a layer-by-layer process by applying a series of digital masks (projected light images). With our current projection and microscopy system, the fabrication of microhydrogel structures with a lateral resolution of 3 \mu \textm and an adjustable thickness ranging from tens of nanometers to hundreds of micrometers has been demonstrated. In summary, this novel technique provides an efficient process for the rapid printing of the 3-D biopolymer-based microstructures, and could enable many future applications in a mechanoanalysis of cancer cells, tissue engineering, and drug screening. [2015-0110] [ABSTRACT FROM AUTHOR]

A technique of casting of thick pre-polymer layers was developed based on the proposed model of diluent evaporation. For the first time, microstructures with 7 mm height and up to 18 microns wide (an aspect ratio of up to 389) were manufactured by means of ultra deep X-ray lithography in a cured pre-polymer that can be functionalized. The microstructures were characterized. The difference in the size of patterned microstructures and their initial size on the X-ray mask decreases to 400 nm with the lessening lateral dimension of the microstructures from 1500 to 18 μm. The sidewall roughness also decreases to 20 nm. [ABSTRACT FROM AUTHOR]

This study aims to examine the effect of annealing conditions on nitinol (NiTi) characteristics and applies this knowledge to fabricate a NiTi-copper shape memory alloy bimorph actuator. The effect of the annealing conditions was investigated at various temperatures, i.e., 500, 600, and 650 °C, for 30 min. With the characterizations using x-ray diffraction, energy dispersive spectroscopy, and differential scanning calorimetry techniques, the results showed that annealing temperatures at 600 and 650 °C were able to appropriately form the crystalline structure of NiTi. However, at these high annealing temperatures, the oxide on a surface was unavoidable. In the fabrication of actuator, the annealing at 650 °C for 30 min was chosen, and it was performed at two pre-stressing conditions, i.e., straight and curved molds. From static and dynamic response experiments, the results suggested that the annealing temperature significantly affected the deflection of the actuator. On the other hand, the effect of pre-stressing conditions was relatively small. Furthermore, the micro gripper consisting of two NiTi-copper bimorph actuators successfully demonstrated for the viability of small object manipulation as the gripper was able to grasp and hold a small plastic ball with its weight of around 0.5 mg. [ABSTRACT FROM AUTHOR]

Electrospun mats from nano/micro-fibers with controlled porosity and pore shape may be ideal candidate for tissue engineering scaffolds. In this study three types of poly(vinyl alcohol) (PVA) mats of 41 µm - 66 µm thickness with different average nano/micro-fibers diameter of 100 nm - 200 nm were deposited on spunbond polypropylene (PP) filaments by electrospinning process. Controlled density porosity in the electrospun mats was introduced by Yb:KGW femtosecond laser micromachining system. The influence of electrospun mat microstructure, the distance between the adjacent laser ablation points, the number of femtosecond laser pulses on quality and structure of the laser irradiated holes were investigated. It was demonstrated that the quality of irradiated holes depends on the structure of electrospun mats (diameter of nano/micro-fibers, thickness of mats) and femtosecond laser processing parameters. Varying the distance between points of laser irradiation as well as number of applied femtosecond laser pulses it is possible to fabricate electrospun mats with increased porosity having extra pores of 22 µm - 36 μm in diameter. [ABSTRACT FROM AUTHOR]

Membrane projection lithography is used to create 3-dimensional unit cells in a silicon matrix decorated with metallic inclusions. The structures show pronounced resonances in the 4-16 lm wavelength range and demonstrate direct coupling to the magnetic field of a normally incident transverse electromagnetic (TEM) wave, a behavior only possible for vertically oriented resonators. Qualitative agreement between rigorous coupled wave analysis (RCWA) simulation and measured scattering response is shown. COMSOL simulations show that slight variations in both metallic inclusion and silicon unit cell physical dimensions can have large impact in the scattering response, so that design for manufacture of 3D metamaterial structures for applications should be done with care. [ABSTRACT FROM AUTHOR]