Hard Mold Research Articles

Polymer microring resonators fabricated by nanoimprint technique

Microring optical resonators have important applications in integrated photonic circuits for optical communications. We have developed two methods to fabricate polymer microring devices based on the nanoimprint technique. The first method uses a hard mold to directly imprint a polymer film to form optical waveguides in microring devices. We have demonstrated polymethylmethacrylate, polystyrene, and polycarbonate microring resonators fabricated using this technique. The second method employs a template filling approach, which allows a thicker waveguide to be fabricated, as well as polymers that are difficult to directly imprint. Optical filtering behavior of a microring resonator is demonstrated with a Q factor as high as 5800. The technique developed in this work could offer a cost-effective method to fabricate integrated photonic circuits based on polymer microring resonators.

Reversal imprinting by transferring polymer from mold to substrate

A reversal imprinting technique was developed in this study. A polymer layer was first spin coated on a patterned hard mold, and then transferred to a substrate under an elevated temperature and pressure. The reversal imprinting method offers an advantage over conventional nanoimprinting by allowing imprinting onto substrates that cannot be easily spin coated, such as flexible polymer substrates. Another unique feature of reversal imprinting is that three different pattern-transfer modes can be achieved by controlling the degree of surface planarization of the mold after spin coating the polymer resist as well as the imprinting temperature. “Embossing” occurs at temperatures well above the glass transition temperature (Tg) of a polymer; “inking” occurs at temperatures around Tg with nonplanarized polymer coating surface on the mold; and “whole-layer transfer” occurs at temperatures around Tg but with a somewhat planarized surface. These three imprinting modes have been quantitatively correlated with the surface planarization of the mold after polymer coating and the imprinting temperature.

New Formation Technology of Plasma Display Panel Barrier-Rib Structure Using Silicone Rubber Mold Transferred from SU-8 Master Structure

A new formation technology for a plasma display panel (PDP) barrier-rib structure is presented to realize a barrier rib with a high aspect ratio and reduce the manufacturing cost. In this study, we used an SU-8 50 photoresist, which is sensitive to UV irradiation, instead of polymethylmethacrylate (PMMA) which is sensitive to X-ray irradiation, so that the silicone rubber mold could be applicable to a large-area PDP. The first step is to produce an SU-8 master structure using amorphous silicon as an adhesion layer between a glass substrate and SU-8 photoresist. Second, a precise soft mold is manufactured for mass replication of the PDP barrier-rib construction, by molding liquid silicone rubber onto the glass substrate with lithographically defined SU-8 master structures. Third, a PDP barrier-rib structure is formed using the pattern-transferring process with a reusable silicone rubber mold. This is a very simple and inexpensive process consisting with printing of barrier-rib paste, drying, pattern-transferring, and sintering. The pattern-transferring process with a soft mold also demonstrates that the disadvantages of the conventional mold pressing process with a hard mold can be overcome. Consequently, by using the pattern-transferring process with the silicone rubber mold transferred from the SU-8 master structure, the desired barrier-rib shapes can be realized with a high aspect ratio and various dimensions.

Rapid Prototyping of Ceramic Components

A variety of techniques has been recently developed to produce parts and prototypes from a computer-aided design (CAD) image without hard tools, dies, or molds. Integration of rapid prototyping technologies – laser sintering, multiphase jet solidification, hot molding etc. – into standard ceramic shaping processes is subject of several current research projects. Using a 3D data set describing the geometry of the ceramic component, complex original models have been developed from rapid prototyping techniques. For a small-production run plastic molds can be used, whereas for a medium- or a high-production run a hardened steel die can be produced based on the correct shrinkage data.

Rapid Prototyping of Ceramic Components

A variety of techniques has been recently developed to produce parts and prototypes from a computer-aided design (CAD) image without hard tools, dies, or molds. Integration of rapid prototyping technologies – laser sintering, multiphase jet solidification, hot molding etc. – into standard ceramic shaping processes is subject of several current research projects. Using a 3D data set describing the geometry of the ceramic component, complex original models have been developed from rapid prototyping techniques. For a small-production run plastic molds can be used, whereas for a medium- or a high-production run a hardened steel die can be produced based on the correct shrinkage data.

Direct nano-printing on Al substrate using a SiC mold

Nanostructures in Al were generated by printing with hard SiC molds. This nano-printing technology replaces the lithography and the etching or deposition processes to produce patterns directly in metal. Dots, short lines, and long lines were formed in the SiC molds by electron beam lithography and reactive ion etching. High aspect ratio features as small as 40 nm with depth up to 840 nm were patterned in the SiC molds. By pressing the SiC mold onto the Al substrate at room temperature, nanostructures in the SiC mold were reproduced accurately and uniformly in Al. Large arrays of nanostructures down to 40 nm were printed in Al with similar results for dots, short lines, and long lines. Using atomic force microscopy to analyze the cross sections of the SiC molds and printed Al nanostructures, depth dependence on feature size was observed. This nano-printing technology simplifies the processes for generating nanostructures with high throughput and high uniformity.

Congenital Atresio Vagina

SummaryMcindoe's method of vaginal reconstruction is simple.Instead of using hard vaginel mould foam form is suggested.Common complications like contraction of cavity, hypergranulation tissue, V.V.F., R.V.F. etc. could be avoided.

Growth of InBi single crystals

Large single crystals (up to 20 cm length and 4 cm diameter) of InBi were grown by hard and soft mold Bridgman, Czochralski and horizontal boat techniques. The crystals were characterized in terms of subgrain mis-orientation and dislocation densities. Dislocation densities were determined by etching in a Br 2/methanol solution. Crystals of highest structural perfection with no observable subgrains and dislocation densities of 0.5−2×10 4/cm 2 were obtained by the Czochralski technique with seeds oriented along 〈 hk0〉 and pulling rates of 3–4cm/hour. Self-nucleated crystals grow rather exclusively with the c-axis perpendicular within 10 degrees to the growth direction.

Substructure control by solidification control in cu crystals

In an attempt to systematically control dislocation substructure, seeded Cu single crystals have been grown from the melt at rates from 1.1 to 730 cm/h. Soft and hard graphite molds are used, with the hard molds surrounded by graphite or firebrick sleeves. In this fashion mold wall characteristics are varied and mold thermal conductivity is changed from 27×10−4 to 0.29×10−4 (cgs units). An increase in growth rate over this range has little effect on random dislocation density, which remains about 1.5×106 cm−2. The increase does cause a decrease in dislocation cell size from about 5×10−2 to 0.5×10−2 cm. The decrease varies approximately as (freezing rate)−1/2 in agreement with the dislocation half-loop model of dislocation generation. An increase of mold thermal conductivity of a factor of 100 has little effect on random density, but causes a 50 to 300 pct increase in cell size. Crystals grown in soft molds have a random density about one-half those grown in hard molds. The cell size is comparable to that obtained with firebricked-sleeved hard molds of similar thermal conductivity. The data indicate that solute effects do not play a significant part in substructure generation in copper of 99.999 pct purity.