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A Novel Fabrication Technique for Liquid-Tight Microchannels by Combination of a Paraffin Polymer and a Photo-Curable Silicone Elastomer.

ABSTRACT: The development and growth of microfluidics has been mainly based on various novel fabrication techniques for downsizing and integration of the micro/nano components. Especially, an effective fabrication technique of three-dimensional structures still continues to be strongly required in order to improve device performance, functionality, and device packing density because the conventional lamination-based technique for integrating several two-dimensional components is not enough to satisfy the requirement. Although three-dimensional printers have a high potential for becoming an effective tool to fabricate a three-dimensional microstructure, a leak caused by the roughness of a low-precision structure made by a 3D printer is a critical problem when the microfluidic device is composed of several parts. To build a liquid-tight microchannel on such a low-precision structure, we developed a novel assembly technique in which a paraffin polymer was used as a mold for a microchannel of photo-curable silicone elastomer on a rough surface. The shape and roughness of the molded microchannel was in good agreement with the master pattern. Additionally, the seal performance of the microchannel was demonstrated by an experiment of electrophoresis in the microchannel built on a substrate which has a huge roughness and a joint.

SUBMITTER: Mogi K

PROVIDER: S-EPMC5509039 | biostudies-other | 2016 Jul

REPOSITORIES: biostudies-other

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3D Printing Low-Stiffness Silicone Within a Curable Support Matrix.

Project description:Embedded 3D printing processes involve extruding ink within a support matrix that supports the ink throughout printing and curing. In once class of embedded 3D printing, which we refer to as "removable embedded 3D printing," curable inks are printed, cured, then removed from the uncured support matrix. Removable embedded 3D printing is advantageous because low-viscosity inks can be patterned in freeform geometries which may not be feasible to create via casting and other printing processes. When printing solid-infill geometries, however, uncured support matrix becomes trapped within the prints, which may be undesirable. This study builds on previous work by formulating a support matrix for removable embedded 3D printing that cures when mixed with the printed silicone ink to solve the problem of trapped, uncured support matrix within solid-infill prints. Printed specimens are shown to have a nearly isotropic elastic modulus in directions perpendicular and parallel to the printed layers, and a decreased modulus and increased elongation at break compared to specimens cast from the ink. The rheological properties of the support matrix are reported. The capabilities of the printer and support matrix are demonstrated by printing a variety of geometries from four UV and addition-cure silicone inks. Shapes printed with these inks range by nearly two orders of magnitude in stiffness and have failure strains between approximately 50 and 250%, suggesting a wide range of potential applications for this printing process.

| S-EPMC7946128 | biostudies-literature

Suspended Liquid Subtractive Lithography: One-step generation of 3D channel geometries in viscous curable polymer matrices.

Project description:The miniaturization of synthesis, analysis and screening experiments is an important step towards more environmentally friendly chemistry, statistically significant biology and fast and cost-effective medicinal assays. The facile generation of arbitrary 3D channel structures in polymers is pivotal to these techniques. Here we present a method for printing microchannels directly into viscous curable polymer matrices by injecting a surfactant into the uncured material via a steel capillary attached to a 3D printer. We demonstrate this technique using polydimethylsiloxane (PDMS) one of the most widely used polymers for the fabrication of, e. g. microfluidic chips. We show that this technique which we term Suspended Liquid Subtractive Lithography (SLSL) is well suited for printing actuators, T-junctions and complex three dimensional structures. The formation of truly arbitrary channels in 3D could revolutionize the fabrication of miniaturized chips and will find broad application in biology, chemistry and medicine.

| S-EPMC5547044 | biostudies-literature

New technique for removal of perfluorocarbon liquid related sticky silicone oil and literature review.

Project description:AimTo investigate the safety and efficacy of sticky silicone oil (SSO) removal using a 22-gauge vein detained needle and inner limiting membrane (ILM) wrap-and-peel technique.MethodsThis retrospective consecutive case series reviewed the records of patients with a history of retinal detachment who had received silicone oil and perfluorocarbon liquid (PFCL) as intraocular tamponades. Patients were included in the analysis if they exhibited SSO remnants during silicone oil removal. The aspiration of most of the SSO remnants was performed by a 22-gauge vein detained needle. The small amounts of droplets adhered to the macula and epi-macular membrane were subsequently removed by the ILM warp-and-peel technique. The anatomical and functional outcomes, and postoperative complications were recorded. In vitro experiments were performed to simulate the formation of SSO remnants in four groups.ResultsOf 711 patients who underwent silicone oil removal during the study period, 9 patients exhibited SSO remnants and underwent follow-up for at least 3mo. Seven eyes (78%) underwent the ILM wrap-and-peel technique to completely remove small droplets of SSO that were glued to the macula and epi-macular membrane. No obvious complications occurred. Postoperative optical coherence tomography revealed normal retinal structure in all patients. In vitro analyses showed that balanced salt solution and prolonged vibration (for 1wk) had the strongest effects on silicone oil and PFCL compound opacities.ConclusionSSO remnants could be removed in an intact manner and without complications, using a vein detained needle-assisted and ILM wrap-and-peel technique. The findings suggest that PFCL and infusion fluid should be completely removed before silicone oil injection to prevent SSO formation.

| S-EPMC8640768 | biostudies-literature

Photo-Responsive Shape-Memory and Shape-Changing Liquid-Crystal Polymer Networks.

Project description:"Surrounding matters" is a phrase that has become more significant in recent times when discussing polymeric materials. Although regular polymers do respond to external stimuli like softening of material at higher temperatures, that response is gradual and linear in nature. Smart polymers (SPs) or stimuli-responsive polymers (SRPs) behave differently to those external stimuli, as their behavior is more rapid and nonlinear in nature and even a small magnitude of external stimulus can cause noticeable changes in their shape, size, color or conductivity. Of these SRPs, two types of SPs with the ability to actively change can be differentiated: shape-memory polymers and shape-changing polymers. The uniqueness of these materials lies not only in the fast macroscopic changes occurring in their structure but also in that some of these shape changes are reversible. This paper presents a brief review of current progress in the area of light activated shape-memory polymers and shape-changing polymers and their possible field of applications.

| S-EPMC5452121 | biostudies-other

Optimized Soft Lithography Method for Polymer Cholesteric Liquid Crystal Flakes Fabrication.

Project description:Polymer cholesteric liquid crystal (PCLC) flakes are gaining increasing interest for a wide variety of applications because of their unique optical properties and capabilities. Soft lithography is the most effective way to fabricate regularly shaped PCLC flakes. However, it is not easy to peel the flakes from the mold without breaking them. In order to peel the PCLC flakes from the patterned polydimethylsiloxane (PDMS) mold in a convenient way, in this paper, a method of coating a layer of polyvinyl alcohol (PVA) on a PDMS mold was proposed. The influence of the thickness of the PVA layer on the shape of the PCLC flakes and the release time from the PDMS mold were investigated. The results show that the presence of the PVA layer can speed up the release of the PCLC flakes and help maintain the shape effectively. Notably, the utilization of a PVA layer makes the PDMS mold recyclable. The influence of PCLC flake shape was also studied. This work will promote the development of switchable PCLC flake-based technologies.

| S-EPMC6680817 | biostudies-literature

Photo Actuation Performance of Nanotube Sheet Incorporated Azobenzene Crosslinked Liquid Crystalline Polymer Nanocomposite.

Project description:Crosslinked liquid crystalline polymers (CLCPs) containing azobenzene (AZO-CLCPs) are a type of promising material due to their significance in the design of light-driven smart actuators. Developing AZO-CLCP composites by incorporating AZO-CLCPs with other materials is an effective way of enhancing their practicability. Herein, we report an AZO-CLCP/CNT nanocomposite prepared by the in situ polymerization of diacrylates containing azobenzene chromophores on carbon nanotube (CNT) sheets. The liquid crystal phase structure of CLCP matrix was evidenced by the two-dimensional X-ray scattering. The prepared pure AZO-CLCP films and AZO-CLCP/CNT nanocomposite films demonstrated strong reversible photo-triggered deformation under the irradiation of UV light at 366 nm of wavelength, as a result of photo-induced isomerization of azobenzene moieties in the polymer network. But compared to pure AZO-CLCP films, the AZO-CLCP/CNT nanocomposite films could much more rapidly return to their initial shapes after the UV light irradiation was removed due to the elasticity effect of CNT sheets. The deformation behavior of AZO-CLCP/CNT nanocomposite films under the light irradiation was also different from that of the pure AZO-CLCP films due to the interfacial interaction between a polymer network and CNT sheet. Furthermore, incorporation of a CNT sheet remarkably increased the mechanical strength and robustness of the material. We also used this AZO-CLCP/CNT nanocomposite as a microvalve membrane actuator, which can be controlled by light, for a conceptual device of a microfluidic system. The results showed that this AZO-CLCP/CNT nanocomposite may have great potential in smart actuator applications for biological engineering, medical treatment, environment detection and microelectromechanical systems (MEMS), etc.

| S-EPMC6523392 | biostudies-literature

Chiral Liquid Crystal Lenses Confined in Microchannels.

Project description:It is known that the liquid crystalline smectic-A phase has geometric defects, called focal conic domains, which can be used as gradient-index microlenses. Cholesteric (chiral nematic) phases also have topological defects with a central symmetry and a singularity at their center. We explore a weakly chiral system in which both types of defects can be present in the same material at different temperatures, and with this strategy we create lenses whose focal length is tunable with temperature. We measure the focal length of the tunable lenses, and we investigate the behavior of the defects near the phase transition. We identify the experimental conditions that make the simultaneous presence of the smectic focal conic domains and the circular cholesteric domains possible, such as the concentration of chiral dopant and the rate of heating and cooling. The transformation of focal conic domains into circular cholesteric domains is a new example of memory at the phase transition between smectic-A and nematic liquid crystals.

| S-EPMC7503803 | biostudies-literature

Electrocapillary Actuation of Liquid Metal in Microchannels.

Project description:Controllable deformation of liquid metal by electrocapillary actuation (ECA) is empirically characterized in fluidic channels at the sub-millimeter-length scale. In 100-µm-deep channels of varying widths, the Galinstan liquid metal could move at velocities of more than 40 mm/s. The liquid metal could extend more than 2.5 mm into the channels at an electrocapillary actuation voltage of 3 V DC. The dynamic behavior of the liquid metal as it moves in the microchannels is described. These results are useful for designing microsystems that use liquid metal as a functional material.

| S-EPMC9032191 | biostudies-literature

Hierarchical porous materials made by stereolithographic printing of photo-curable emulsions.

Project description:Porous materials are relevant for a broad range of technologies from catalysis and filtration, to tissue engineering and lightweight structures. Controlling the porosity of these materials over multiple length scales often leads to enticing new functionalities and higher efficiency but has been limited by manufacturing challenges and the poor understanding of the properties of hierarchical structures. Here, we report an experimental platform for the design and manufacturing of hierarchical porous materials via the stereolithographic printing of stable photo-curable Pickering emulsions. In the printing process, the micron-sized droplets of the emulsified resins work as soft templates for the incorporation of microscale porosity within sequentially photo-polymerized layers. The light patterns used to polymerize each layer on the building stage further generate controlled pores with bespoke three-dimensional geometries at the millimetre scale. Using this combined fabrication approach, we create architectured lattices with mechanical properties tuneable over several orders of magnitude and large complex-shaped inorganic objects with unprecedented porous designs.

| S-EPMC8595381 | biostudies-literature

Droplet Formation by Confined Liquid Threads inside Microchannels.

Project description:A confined liquid thread can form monodisperse droplets near the exit of a microchannel, provided the continuous phase is able to enter the microchannel. A general model that accurately predicts the droplet size including the breakup position inside the microchannel is presented and is verified with experimental observations; breakup occurs as long as the capillary number (Ca) of the liquid thread is below a critical capillary number (Cacr); for cylindrical microchannels, it is derived that Cacr = 1/16. Below Cacr, the formed droplets at the exit of the microchannel have a diameter approximately two times the diameter of the liquid thread; around and above Cacr, the liquid thread remains stable and the formed droplets grow infinitely large. The presented controlled droplet generation method is a useful tool for producing monodisperse emulsions and has great potential for the food and pharmaceutical industry.

| S-EPMC5618148 | biostudies-literature

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