1,721,054 research outputs found
Micro 3D Printing Using a Digital Projector and its Application in the Study of Soft Materials Mechanics
No full textBuckling is a classical topic in mechanics. While buckling has long been studied as one of the major structural failure modes, it has recently drawn new attention as a unique mechanism for pattern transformation. Nature is full of such examples where a wealth of exotic patterns are formed through mechanical instability. Inspired by this elegant mechanism, many studies have demonstrated creation and transformation of patterns using soft materials such as elastomers and hydrogels. Swelling gels are of particular interest because they can spontaneously trigger mechanical instability to create various patterns without the need of external force. Recently, we have reported demonstration of full control over buckling pattern of micro-scaled tubular gels using projection micro-stereolithography (PμSL), a three-dimensional (3D) manufacturing technology capable of rapidly converting computer generated 3D models into physical objects at high resolution. Here we present a simple method to build up a simplified PμSL system using a commercially available digital data projector to study swelling-induced buckling instability for controlled pattern transformation.
A simple desktop 3D printer is built using an off-the-shelf digital data projector and simple optical components such as a convex lens and a mirror. Cross-sectional images extracted from a 3D solid model is projected on the photosensitive resin surface in sequence, polymerizing liquid resin into a desired 3D solid structure in a layer-by-layer fashion. Even with this simple configuration and easy process, arbitrary 3D objects can be readily fabricated with sub-100 μm resolution.
This desktop 3D printer holds potential in the study of soft material mechanics by offering a great opportunity to explore various 3D geometries. We use this system to fabricate tubular shaped hydrogel structure with different dimensions. Fixed on the bottom to the substrate, the tubular gel develops inhomogeneous stress during swelling, which gives rise to buckling instability. Various wavy patterns appear along the circumference of the tube when the gel structures undergo buckling. Experiment shows that circumferential buckling of desired mode can be created in a controlled manner. Pattern transformation of three-dimensionally structured tubular gels has significant implication not only in mechanics and material science, but also in many other emerging fields such as tunable matamaterials.Peer reviewed
First jump of microgel; actuation speed enhancement by elastic instability
No full textSwelling-induced snap-buckling in a 3D micro hydrogel device, inspired by the insect-trapping action of Venus flytrap, makes it possible to generate astonishingly fast actuation. We demonstrate that elastic energy is effectively stored and quickly released from the device by incorporating elastic instability. Utilizing its rapid actuation speed, the device can even jump by itself upon wetting.Peer reviewed
Solvent-driven polymeric micro beam device
No full textThe response of current hydrogel devices mainly depends on the diffusion of stimuli. However, diffusion is a slow transport mechanism compared to advection, which therefore limits the response speed of hydrogel devices. To overcome this limitation, we introduce a capillary network and elastic instability mechanism. Particularly, an open surface capillary delivers and distributes solvent, thus triggering the swelling and bending of curved polymeric beams. To demonstrate this concept, we fabricate these polymeric microstructures using projection micro-stereolithography (PμSL). Combined with instability criteria analysis based on static beam theory, this device is designed to exhibit two-way snap-through behavior. Our analysis provides the minimum dimensionless stiffness β for the beam device to snap during solvent actuation. Here, β is a well-defined dimensionless parameter in our analysis that indicates whether the device can provide sufficient axial force to trigger the snap-through of the beam. The actuation displacement can be as high as 45% of the length of the beam. We observe a maximum midpoint speed of 3.1 cm s−1 for a beam 2 mm long—20 times higher than that for a beam without an elastic instability mechanism. This device can be used in artificial muscle and as the key component for fluidic-to-mechanical signal transduction in active micro-fluidic circuits.Peer reviewedAccepted Manuscript provided by publisher and distributed with permission
Prescribed Pattern Transformation in Swelling Gel Tubes by Elastic Instability
No full textWe present a study on swelling-induced circumferential buckling of tubular shaped gels. Inhomogeneous stress develops as gel swells under mechanical constraints, which gives rise to spontaneous buckling instability without external force. Full control over the postbuckling pattern is experimentally demonstrated. A simple analytical model is developed using elastic energy to predict stability and post-buckling patterns upon swelling. Analysis reveals that height to diameter ratio is the most critical design parameter to determine buckling pattern, which agrees well with experimental and numerical results.Peer reviewed
Multimaterial 4D Printing with Tailorable Shape Memory Polymers
No full textWe present a new 4D printing approach that can create high resolution (up to a few microns), multimaterial shape memory polymer (SMP) architectures. The approach is based on high resolution projection microstereolithography (PμSL) and uses a family of photo-curable methacrylate based copolymer networks. We designed the constituents and compositions to exhibit desired thermomechanical behavior (including rubbery modulus, glass transition temperature and failure strain which is more than 300% and larger than any existing printable materials) to enable controlled shape memory behavior. We used a high resolution, high contrast digital micro display to ensure high resolution of photo-curing methacrylate based SMPs that requires higher exposure energy than more common acrylate based polymers. An automated material exchange process enables the manufacture of 3D composite architectures from multiple photo-curable SMPs. In order to understand the behavior of the 3D composite microarchitectures, we carry out high fidelity computational simulations of their complex nonlinear, time-dependent behavior and study important design considerations including local deformation, shape fixity and free recovery rate. Simulations are in good agreement with experiments for a series of single and multimaterial components and can be used to facilitate the design of SMP 3D structures.Peer reviewe
Design and optimization of a light-emitting diode projection micro-stereolithography three-dimensional manufacturing system
No full textThe rapid manufacture of complex three-dimensional micro-scale components has eluded researchers for decades. Several additive manufacturing options have been limited by either speed or the ability to fabricate true three-dimensional structures. Projection micro-stereolithography (PμSL) is a low cost, high throughput additive fabrication technique capable of generating three-dimensional microstructures in a bottom-up, layer by layer fashion. The PμSL system is reliable and capable of manufacturing a variety of highly complex, three-dimensional structures from micro- to meso-scales with micro-scale architecture and submicron precision. Our PμSL system utilizes a reconfigurable digital mask and a 395 nm light-emitting diode (LED) array to polymerize a liquid monomer in a layer-by-layer manufacturing process. This paper discusses the critical process parameters that influence polymerization depth and structure quality. Experimental characterization and performance of the LED-based PμSL system for fabricating highly complex three-dimensional structures for a large range of applications is presented.Peer reviewe
Biomimetic microactuator powered by polymer swelling
No full textWe propose novel biomimetic polymer microactuators. The actuation mechanism is inspired by nastic movement of the moving plant, Mimosa pudica, which folds its leaves upon external stimulus by regulating turgor pressure of cells in specific location. Photo-cured poly(ethylene glycol) diacrylate (PEGDA) microactuator is fabricated using projection microstereolithography (PμSL) capable of complex 3D micro fabrication. The swelling effect of PEG in water and organic solvent is exploited as an actuation mechanism of the device. Stress relaxation in the structure due to solvent absorption is controlled locally by delivering solvent through microfluidic channels embedded in the actuator, thereby generating a net movement in the device. Timescale of the motion derived from analytical swelling model suggests that actuation speed can be effectively increased by scaling down the actuator because the characteristic swelling time depends on the length as L2, which is verified experimentally. Copyright © 2008 by ASME.N
Micro 3D Printing Using a Digital Projector and its Application in the Study of Soft Materials Mechanics
No full textBuckling is a classical topic in mechanics. While buckling has long been studied as one of the major structural failure modes(1), it has recently drawn new attention as a unique mechanism for pattern transformation. Nature is full of such examples where a wealth of exotic patterns are formed through mechanical instability(2-5). Inspired by this elegant mechanism, many studies have demonstrated creation and transformation of patterns using soft materials such as elastomers and hydrogels(6-11). Swelling gels are of particular interest because they can spontaneously trigger mechanical instability to create various patterns without the need of external force(6-10). Recently, we have reported demonstration of full control over buckling pattern of micro-scaled tubular gels using projection micro-stereolithography (P mu SL), a three-dimensional (3D) manufacturing technology capable of rapidly converting computer generated 3D models into physical objects at high resolution(12,13). Here we present a simple method to build up a simplified P mu SL system using a commercially available digital data projector to study swelling-induced buckling instability for controlled pattern transformation. A simple desktop 3D printer is built using an off-the-shelf digital data projector and simple optical components such as a convex lens and a mirror(14). Cross-sectional images extracted from a 3D solid model is projected on the photosensitive resin surface in sequence, polymerizing liquid resin into a desired 3D solid structure in a layer-by-layer fashion. Even with this simple configuration and easy process, arbitrary 3D objects can be readily fabricated with sub-100 mu m resolution. This desktop 3D printer holds potential in the study of soft material mechanics by offering a great opportunity to explore various 3D geometries. We use this system to fabricate tubular shaped hydrogel structure with different dimensions. Fixed on the bottom to the substrate, the tubular gel develops inhomogeneous stress during swelling, which gives rise to buckling instability. Various wavy patterns appear along the circumference of the tube when the gel structures undergo buckling. Experiment shows that circumferential buckling of desired mode can be created in a controlled manner. Pattern transformation of three-dimensionally structured tubular gels has significant implication not only in mechanics and material science, but also in many other emerging fields such as tunable matamaterials.Y
Recent advances in multi-material additive manufacturing: methods and applications
No full textMulti-material additive manufacturing (MMAM) enables rapid design and direct fabrication of three-dimensional (3D) objects consisting of multiple materials without the need for complex manufacturing process and expensive tooling. Through concurrent integration of multiple materials having their own unique properties, MMAM allows for facile production of multi-functional devices and systems. Various MMAM techniques have recently been developed and a wide range of new applications have been demonstrated using MMAM. This paper reviews recent advances in MMAM methods and key applications enabled by MMAM in three areas; biomedical engineering, soft robotics, and electronics.N
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