Polymer Tip Research Articles

Aqualase for cataract extraction

To report our experience of using Aqualase technology for cataract extraction. In total, 33 patients (20 females; mean age 71.4 years) underwent cataract surgery using Aqualase through a 3.2-mm corneal incision. Grade of nucleus, nuclear removal technique, and intraoperative complications were noted. Clinical parameters from postoperative visits were collected. Aqualase is capable of removing cataracts up to nuclear sclerosis 2+ (out of 4) with relative ease. Nuclei graded 2+ or greater were technically more difficult and conversion to ultrasound phacoemulsification was required in one case. Two posterior capsule ruptures occurred: one during nucleus removal (contact with the tip while aspirating without Aqualase) and one unrelated to Aqualase during aspiration of cortex. Of 25 patients seen on the first postoperative day, 22 had a clear cornea. A total of 96% patients without preoperative comorbidity achieved 6/9 or better postoperatively. One patient had transient postoperative uveitis. Removal of softer cataracts with Aqualase has the theoretical advantage over phacoemulsification, by carrying less risk to the posterior capsule, since the handpiece has a smooth polymer tip that has no mechanical motion inside the eye. However, the tip should not be considered entirely capsule-friendly, as rupture is possible with the foot-pedal in position two (aspiration only). Although certain adjustments to the technique are required, the method is similar enough to phacoemulsification to ensure a brief learning curve. With increasingly firm cataracts, Aqualase becomes less effective and ultrasound phacoemulsification is still superior for such cases, in our experience.

Coupling semiconductor lasers into single-mode optical fibers by use of tips grown by photopolymerization.

We show that a polymer tip, integrated by free-radical photopolymerization at the end of a telecommunication optical fiber, allows high-efficiency coupling between the fiber and an infrared laser diode. A coupling efficiency of 70% (1.5-dB loss) was achieved. We obtained this result by controlling the radius of curvature of the tip, the origin of which is discussed in terms of the photochemical influence of oxygen during tip formation. The experimental data were found to be in agreement with results of electromagnetic calculations based on the finite-element method.

Sheathless Electrospray from Polymer Microchips

In this study, sheathless electrospray from polymer microchips with conducting layer on the emitter tip is described for the first time. The electrospray emitter tips were fabricated directly from the end of the microchips that were made of polycarbonate or poly(methyl methacrylate) with injection molding. A variety of tip shapes and conducting coatings were evaluated using an electrospray time-of-flight mass spectrometer run in the sheathless mode. Stable electrospray was obtained both from hand-polished and machine-milled three-dimensional tips coated with either polymer-embedded gold particles or graphite particles as the conducting layer. Sputtered gold, on the other hand, suffered from poor stability mainly due to bad adhesion to the polymer tip. The durability of the different coatings was confirmed with electrochemical experiments under simulated electrospray conditions. The relative standard deviations of the response received from the ion current of the MS analysis were in the range of 3.5-12%. The detection limit for a standard mixture containing five neuropeptides was lower than 0.5 fmol. The low detection limit makes the emitter tips highly attractive for the analysis of low-abundance biological species.

An electrospray ionization source for integration with microfluidics.

We have demonstrated a new electrospray ionization (ESI) device incorporating a tip made from a shaped thin film, bonded to a microfluidic channel, and interfaced to a time-of-flight mass spectrometer (TOFMS). A triangular-shaped thin polymer tip was formed by lithography and etching. A microfluidic channel, 20 microm wide and 10 microm deep, was embossed in a cyclo olefin substrate using a silicon master. The triangular tip was aligned with the channel and bonded between the channel plate and a flat plate to create a microfluidic channel with a wicking tip protruding from the end. This structure aided the formation of a stable Taylor cone at the apex of the tip, forming an electrospray ionization source. This source was tested by spraying several solutions for mass spectrometric analysis. Because the components are all made by lithographic approaches with high geometrical fidelity, an integrated array system with multiple channels can be formed with the same method and ease as a single channel. We tested a multichannel system in a multiplexed manner and showed reliable operation with no significant cross contamination between closely spaced channels.

End-of-fiber polymer tip: manufacturing and modeling

A flexible method of manufacturing polymer elements at the extremity of both single mode and multimode optical fibers is reported. The procedure consists in depositing a drop of liquid photopolymerizable formulation on the cleaved fiber and using the light emerging from the fiber to induce polymerization process. After exposure and rinsing with methanol, a polymer tip is firmly attached to the fiber as an extension of the fiber core. When this process is applied to a multimode fiber, the fabricated polymer element can be the 3D mold of a pre-selected linearly polarized (LP) mode of the fiber. A numerical calculation (consisting on a beam propagation method (BPM) in a medium whose refractive index is time-varying) has shown that our method is based on a gradual growth, just above the fiber core, of an optical waveguide in the liquid formulation. At the end of this paper, potential uses of the obtained tipped-fibers are hinted.

Integration of micrometer-sized polymer elements at the end of optical fibers by free-radical photopolymerization

A simple method of manufacturing micrometer-sized polymer elements at the extremity of both single-mode and multimode optical fibers is reported. The procedure consists of depositing a drop of a liquid photopolymerizable formulation on a cleaved fiber and using the light that emerges from the fiber to induce the polymerization process. After exposure and rinsing a polymer tip is firmly attached to the fiber as an extension of the fiber core. It is shown that the tip geometry can be adjusted by the variation of basic parameters such as the geometry of the deposited drop and the conditions of drop illumination. When this process is applied to a multimode fiber three-dimensional molds of the fiber's linearly polarized modes can be obtained. The process of polymer-tip formation was simulated by a numerical calculation that consisted of an iterative beam-propagation method in a medium whose refractive index is time varying. It is shown that this process is based on the gradual growth, just above the fiber core, of an optical waveguide in the liquid formulation. Experimental data concerning two potential uses of the tipped fibers are presented.

Integration of polymer elements at the end of optical fibers by free-radical photopolymerization

In this article, we report a method of free-radical photopolymerization on the top end of a single-mode optical fiber. The process is very simple to carry out and uses the visible light guided in the fiber. It permits one to produce, on the fiber end, a micronic polymer tip which may be viewed as an extension of the fiber core and whose optical properties improve the intrinsic capability of the fiber, particularly in terms of efficiency of coupling with a laser source. Formation of the tip is explained by self-guiding of the light within the material and photophysical response of the material.

Predicted Effects of Tritium Exposure on Fast-Acting Piezoelectric Valves for Gas Fueling at TFTR

The prospects for using piezoelectrically-driven valves with elastomeric or thermoplastic poppets in tritium gas service have been investigated. A modelling study of a typical valve incorporating ethylene-propylene rubber (EPR) or high density polyethylene (HDPE) was performed. Equations were developed linking applied voltage; ceramic bimorph preloading force, elastic deflection modulus, and specific deflection force (per volt applied); polymer elastic modulus, thickness, seal surface area, and compression (to make seal); elastomer compression set; thermoplastic creep modulus; and flow gap between seat and polymer tip. It was determined that, while EPR should seal the valve orifice more easily, HDPE should produce a valve flow rate vs. voltage curve less variant with time and exposure. Both should, however, be sealable and allow flow curves perturbed by less than or equal to 10% of full scale after ~100 days of exposure to 10{sup}5 Pa (1 atm) T{sub}2 gas (equivalent to ~7 x 10{sup}7 rad = 7 x 10{sup}5 Gy dosage).