The selective light absorption of prestretched thermoplastic polymeric films enables wireless photothermal shape morphing from two-dimensional Euclidean geometry of films to three-dimensional (3D) curvilinear architectures. For a facile origami-inspired programming of 3D folding, black inks are printed on glassy polymers that are used as hinges to generate light-absorption patterns. However, the deformation of unpatterned areas and/or stress convolution of patterned areas hinder the creation of accurate curvilinear structures. In addition, black inks remain in the film, prohibiting the construction of transparent 3D architectures. In this study, we demonstrate the facile preparation of transparent 3D curvilinear structures with the selection of the curvature sign and chirality via the selective light absorption of detachable tapes. The sequential removal of adhesive patterns allowed sequential folding and the control of strain responsivity in a single transparent architecture. The introduction of multiple heterogeneous nonresponsive materials increased the complexity of strain engineering and functionality. External stimuli responsive kirigami-based bridge triggered the multimaterial frame to build the Gaussian curvature. Conductive material casted on the film in a pattern retained the conductivity, despite local deformation. This type of tape patterning system, adopting various materials, can achieve multifunction including transparency and conductivity.

Focused ion beam (FIB) has been applied to micro/nanometer-scale fabrication to control surface functions with the surface topographies. Although the resolution of the FIB sputtering is in the nanometer-scale range in positioning, the removal shape in the depth direction cannot be controlled numerically. This study presents a removal model to predict the surface profile in the simulation. The removal rate depends on not only the ion beam intensity but also the incident angle onto the surface to be structured. The removal model considers the effects of those two parameters to control the surface profile in sputtering. The removal rates in sputtering of the inclined surfaces at incident angles are associated with a Gaussian distribution. The parameters in the model were identified to minimize the simulation error validated against the sputtering tests. The presented model was applied to simulate the microscale structures on surfaces using the identified parameters. The simulation was validated in comparison with the actual machined shapes.

Inkjet printing is a promising technique for printed micro-electronics due to low cost, customizability and compatibility with large-area, flexible substrates. However, printed line shapes can suffer from bulges at the start of lines and at corner points in 2D line patterns. The printed pattern can be multiple times wider than the designed linewidth. This can severely impact manufacturing accuracy and achievable circuit density. Bulging can be difficult to prevent without changing the ink-substrate-system, the drying conditions or the circuit design, all of which can be undesirable. Here, we demonstrate a novel printing methodology that solves this issue by changing the order in which drops are placed on the substrate. The pattern is split up into segments of three drops where the central drop is printed last. This symmetric printing prevents the unwanted ink flow that causes bulging. Larger bulge-free patterns are created by successively connecting segments. Line formation in both traditional linear printing and our novel segmented and symmetric printing was analyzed to understand and optimize results. The printing of X-, T-, and L-shapes is considerably improved compared with the traditional linear printing methodology.

Engineered microenvironments along with robust quantitative models of cell shape metrology that can decouple the effect of various well-defined cues on a stem cell's phenotypic response would serve as an illuminating tool for testing mechanistic hypotheses on how stem cell fate is fundamentally regulated. As an experimental testbed to probe the effect of geometrical confinement on cell morphology, three-dimensional (3D) poly( ε -caprolactone) (PCL) layered fibrous meshes are fabricated with an in-house melt electrospinning writing system (MEW). Gradual confinement states of fibroblasts are demonstrated by seeding primary fibroblasts on defined substrates, including a classical two-dimensional (2D) petri dish and porous 3D fibrous substrates with microarchitectures tunable within a tight cellular dimensional scale window (1–50 μ m). To characterize fibroblast confinement, a quantitative 3D confocal fluorescence imaging workflow for 3D cell shape representation is presented. The methodology advanced allows the extraction of cellular and subcellular morphometric features including the number, location, and 3D distance distribution metrics of the shape-bearing focal adhesion (FA) proteins.

In the layer-based additive manufacturing (AM) processes, a three-dimensional (3D) model is converted into a set of two-dimensional (2D) layers. Due to such conversion, one of the major problems in the layer-based AM processes is the poor surface finish associated with the layer-based stair-stepping effect. However, the surface finish is critical for various microscale applications such as micro-optics and microfluidics. The adoption of AM technologies as a means for fabricating end-use microcomponents and tooling has been limited by such poor surface finish. The aim of this research work is to apply the state-of-the-art meniscus approach and controlled cure depth planning in the mask image projection-based microstereolithography (MIP-μSL) process to address its surface finish challenge. Mathematical models of meniscus shapes and cure depths are developed for the MIP-μSL process. Related process parameters including the minimum meniscus points, sliced layer shapes for forming meniscus, grayscale image values, and Z offsetting values are optimized to achieve the minimum approximation errors between a built part and a given nominal geometric model. A set of test cases with various curved surfaces are designed to test the developed smooth surface fabrication method. The experimental results verify the effectiveness of the proposed methods for the MIP-μSL process.

The scale-up of microcontact printing (μCP) to a roll-to-roll technique for large-scale surface patterning requires scalable tooling for continuous pattern printing with μm-scale features (e.g., 1–50 μm). Here, we examine the process of creating such a tool using an optical direct-write or “maskless” method working on a rotating cylindrical substrate. A predictive model of pattern formation is presented along with experimental results to examine the key control factors for this process. It is shown that factors can be modulated to vary the cross-sectional shape in addition to feature height and width. This feature can then be exploited to improve the robustness of the final printing process.

Traditionally, micromixing has been thought to be governed by molecular diffusion. However, the authors consider that advection is important in the mixing enhancement and applicable to micromixing devices in many industrial fields. Here, the Marangoni convection, a type of shear flow induced at gas–liquid free interfaces, is introduced as an additional source for micromixing. To evaluate the proposal, two liquids with different surface tensions values were mixed in a capillary channel fabricated by the photolithography technique. The utility of Marangoni convection was confirmed in rapid mixing by the flow experiments.

Microtexturing of surfaces has various applications that often involve texturing over large (macroscale) areas with high precision and resolution. This demands scalability and speed of texturing while retaining feature sizes of the order of a few microns. Microchannels are a versatile microfeature, which are often used in microfluidic devices and can be arrayed or joined to form patterns and free-form geometries. We present a technique to fabricate microchannels on surfaces with high-speed and by using a multimaterial process, namely, laser induced plasma micromachining (LIPMM). The process has the potential to machine metals, ceramics, polymers, and other transparent, brittle, and hard-to-machine materials. The presented technique uses an optical system to modify the laser spot into the shape of a line, to fabricate microchannels directly without scanning as in the case of a regular circular spot. The process schematics are shown, and micromachining experiments on polished aluminum are discussed. Moreover, it is shown that the depth and width of the channels may be varied by changing process parameters like the pulse energy, pulse frequency, and number of exposures.

Low energy-short pulsed electric discharge coupled with precise movement of circular electrode in micro-electrical discharge-milling (μ-EDM-milling) enables generation of three-dimensional (3D) cavities in the order of few tens of microns. Use of unshaped rotating electrode alters the spark discharge pattern that is primarily driven by the shape and size of the cavities being machined. In this paper, effects of five different cavities: circular, triangular, square, channel, and cross channel (square pillars) on the machining performance have been studied. These cavities having a nominal dimension of 1000 μm were machined on steel sample using 200 μm tungsten carbide electrode. The machining performance has been evaluated by analyzing dimensional accuracy, surface integrity, profile error, and formation of recast layers. The results highlight significant shape effect on machining performance in μ-EDM-milling. Circular holes machined by die sinking (tool advancement in Z-axis) are found to be more accurate, and square shaped pillars machined in two settings by generating cross channels at 90 deg have poor dimensional control. On the other hand, triangular cavities have the highest surface finish and profile uniformity compared to other shapes. The microscopic study in scanning electron microscopy (SEM) reveals significant variations in globule formation, recast layer deposition, flow of eroded molten metal, and final shape of cavities, which are found to be dependent of tool rotation.

A new process, decoupled functional imprint lithography (D-FIL), is presented for fabricating low elastic modulus polymeric nanocarriers possessing Young's modulus of bulk material as low as sub-1 MPa. This method is employed to fabricate sub-50 nm diameter cylinders with >3:1 aspect ratio and other challenging shapes from low elastic modulus polymers such as N-isopropylacrylamide (NIPAM) and poly(ethylene glycol) di-acrylate (PEGDA), possessing Young's modulus of bulk material <10 MPa which is cannot otherwise be imprinted in similar size and pitch using existing imprint techniques. Standard imprint lithography polymers have Young's modulus >1 GPa, and so these polymers used in nanocarrier fabrication in comparison have very low elastic modulus. Monodispersed, shape- and size-specific nanocarriers composed of NIPAM with material elastic modulus of <1 MPa have been fabricated and show thermal responsive behavior at the lower critical solubility temperature (LCST) of ∼32 °C. In addition, re-entrant shaped nanocarriers composed of PEGDA with elastic modulus <10 MPa are also fabricated. Nanocarriers fabricated from PEGDA are shown with model imaging agent and anticancer drug (Doxorubicin) encapsulated in as small as 50 nm cylindrical nanocarriers.

The advancement of micro tube hydroforming (THF) technology has been hindered by, among others, the lack of robust microdie systems that could facilitate hydroforming of complex parts that require both expansion and feeding. This paper proposes a new micro-THF die assembly that is based on floating a microdie-assembly in a pressurized chamber. The fluid pressure inside the chamber which surrounds the dies and punches is the same as the pressure required to hydroform the tube. The fluid pressure intensity in the chamber varies in accordance with the predetermined pressure loading path required to successfully hydroform the part. The system was built, and hydroforming experiments were carried out for various micro- and meso-scale shapes, including bulge-shapes, Y-shapes, and T-shapes.

Near-field electrohydrodynamic jet (E-jet) printing has recently gained significant interest within the manufacturing research community because of its ability to produce micro/submicron-scale droplets using a wide variety of inks and substrates. However, the process currently operates in open-loop and as a result suffers from unpredictable printing quality. The use of physics-based, control-oriented process models is expected to enable closed-loop control of this printing technique. The objective of this research is to perform a fundamental study of the substrate-side droplet shape-evolution in near-field E-jet printing and to develop a physics-based model of the same that links input parameters such as voltage magnitude and ink properties to the height and diameter of the printed droplet. In order to achieve this objective, a synchronized high-speed imaging and substrate-side current-detection system is implemented to enable a correlation between the droplet shape parameters and the measured current signal. The experimental data reveals characteristic process signatures and droplet spreading regimes. The results of these studies served as the basis for a model that uses the measured current signal as its input to predict the final droplet diameter and height. A unique scaling factor based on the measured current signal is used in this model instead of relying on empirical scaling laws found in prior E-jet literature. For each of the three inks tested in this study, the average error in the model predictions is under 10% for both the diameter and the height of the steady-state droplet. While printing under nonconducive ambient conditions of low relative humidity and high temperature, the use of the environmental correction factor in the model is seen to result in a 17% reduction in the model prediction error.

Incremental forming (IF) is a relatively new technique that uses a simple hemispherical ended tool moving along a predefined three-dimensional toolpath to deform a sheet of metal into the desired shape. The greater process flexibility and higher formability in IF have resulted in greater academic and industrial interest in this process as it can successfully produce ultrathin parts beyond the forming limit seen in conventional stamping and the process does not require any geometry-specific tooling. Another emerging paradigm in manufacturing has been the increasing application of forming in micromanufacturing. The above stated process characteristics of IF make it an ideal candidate for being incorporated into the micromanufacturing paradigm. This work investigates micro-IF to examine how forces and occurrence of sheet failure change when the geometric dimensions of incremental forming are scaled down. The development of a highly repeatable micro-IF experimental setup is described and experiments are performed to show that a previously unknown buckling mode of deformation exists in micro-incremental forming, that is linked to the material microstructure. The analysis provides guidelines for the design and understanding of the micro-incremental forming process.