Polymer Tip Research Articles

EE434 Benefits of a Polymer Tip in Torsional Phacoemulsification: A Targeted Literature Search and Budget Impact Model

EE434 Benefits of a Polymer Tip in Torsional Phacoemulsification: A Targeted Literature Search and Budget Impact Model

The force at the implant cannot be assessed by the mallet force-Unless supported by a model.

The implantation of uncemented prostheses requires the application of sufficient forces to achieve a press-fit of the implant in the bone. Excessive forces have to be omitted to limit bone damage. Force measurements along the force transmission path between mallet and implant are frequently used to investigate this trade-off. Placing a load cell at a position of interest (PoI), which might be the implant bone interface or the head taper junction, is technically challenging or even impossible so that nearby positions are chosen. Thus, a certain inertia and stiffness remain between the PoI and the sensor, and consequently the measured dynamic forces differ from those at the PoI. This experimental and numerical study aimed to investigate the amount of force reduction along the transmission path while joining femoral heads to stem tapers. Forces were measured in vitro at the tip of the mallet, directly above the polymer tip of the impactor and below the stem taper. Springs and masses were used to represent the responding tissue of a patient. A semi-empirical numerical model of the force transmission path was developed and validated in order to simulate a larger range of responding tissue properties than experimentally possible and to investigate the influence of different surgical instruments. A distinct attenuation was observed since the peak forces at the impactor reached 35% of the applied peak forces and 21% at the stem taper, respectively. The force curves were replicated with a median root mean square error of 3.8% of the corresponding mallet blow for the impactor and 3.6% for the stem. The force measurement position and the used surgical instruments have a strong influence on the measured forces. Consequently, the exact measurement conditions with regard to sensor positioning and used surgical instruments have to be specified and hence only studies with similar setups should be compared to avoid misestimation of the forces at the PoI. The proposed dynamic numerical model is a useful tool to calculate the impact of the chosen or changed mechanical parameters prior to executing experiments and also to extrapolate the effect of changing the applied forces to the resulting forces at the PoI.

Efficiency of a polymer-coated phacoemulsification tip in cataract surgery.

To determine whether there is a difference in efficiency during phacoemulsification when using the hybrid polymer tip compared with the metal balanced tip, as measured by cumulative dissipated energy (CDE) and total procedure time. John A. Moran Eye Center, University of Utah, Salt Lake City, Utah. Experimental study. Phacoemulsification was performed with the Centurion Vision System and Infiniti OZil handpiece, with a 30-degree bevel metal balanced tip and hybrid polymer tip. The vacuum was set at 500 mm Hg and the aspiration flow rate at 50 mL/min. Power was changed for torsional and longitudinal ultrasound (US) at 20%, 40%, 60%, 80%, and 100%. Hardened porcine lenses were cut into 200 two mm cubes, 10 for each specified tip/power setting. They were placed into an artificial anterior chamber filled with a balanced salt solution, and phacoemulsification was performed. A second observer randomly assigned the US type and power. The same observer timed trials with a stopwatch, and CDE was recorded. There were no significant differences in time or CDE for any power levels or US modes when comparing the 2 tips. No significant difference in efficiency was observed when comparing the metal balanced tip with the hybrid polymer tip. Given the known improved safety profile and the overall equivalent efficiency of the hybrid tip, it could improve the performance of beginning and advanced surgeons in the future. Future study is needed to evaluate other setting combinations and to evaluate the hybrid tip in clinical settings.

Polymer Microtip-Based Fabry-Perot Interferometer for Water Content Determination in the Gas and Liquid Phase.

In this work, we present a Fabry-Perot interferometer (FPI) based on a polymer microtip for water content determination in both the gas and liquid phase. The polymer tip of pentaerythritol triacrylate (PETA) is fabricated at the end of an optical fiber by self-guiding photopolymerization, forming at the same time a low-fineness Fabry-Perot interferometer and a sensing layer for water thanks to hydroxyl groups present in PETA. The PETA tip shows a clear interferometric signal, which is highly sensitive to the change of the water content in the environment. The FPI signal shifts with a constant sensitivity of 90 pm/%RH, which corresponds to a relative sensitivity of 104 ppm/% RH, in the range of relative humidity from 30 to 80%. In liquid, the FPI sensor shows a nonlinear sensitivity, up to 158 pm/wt % as the water content is below 40 wt % in water/glycerol mixtures. The cross effect of the temperature on the PETA tip is demonstrated to be negligible as the FPI signal is insensitive to temperature changes from 23 to 70 °C. More importantly, the interaction between the tip and the environment affecting the FPI signal is demonstrated experimentally. The proposed FPI sensor is therefore promising for the direct, sensitive, and reliable determination of the water content of products.

Advanced active polymer probe for near-field optics.

We report on a novel, to the best of our knowledge, active probe for scanning near-field optical microscopy (SNOM). A fluorescent nanosphere, acting as the secondary source, is grafted in an electrostatic manner at the apex of a polymer tip integrated into the extremity of an optical fiber. Thanks to the high photostability and sensitivity of the secondary source, the near-field interaction with a gold nanocube is investigated. It is shown that the spatial resolution is well defined by the size of the fluorescent nanosphere. The polarization-dependent near-field images, which are consistent with the simulation, are ascribed to the local excitation rate enhancement. Meanwhile, measurement of the distance-dependent fluorescence lifetime of the nanosphere provides strong evidence that the local density of states is modified so that extra information on nano-emitters can be extracted during near-field scanning. This advanced active probe can thus potentially broaden the range of applications to include nanoscale thermal imaging, biochemical sensors, and the manipulation of nanoparticles.

A pilot study for colorectal carcinoma screening by instant metabolomic profiles using conductive polymer spray ionization mass spectrometry

BackgroundThe rapid and accurate discrimination of colorectal carcinoma (CRC) and polyps at the molecular level enables early intervention of CRC, which can greatly improve the 5-year survival rate of patients. Here we reported the potential of conductive polymer spray ionization mass spectrometry (CPSI-MS) in successfully screening CRC according to the serum metabolic profile. MethodsTrace intravenous blood (50 μL) was collected from 60 colorectal carcinoma (CRC) and 60 polyp patients, respectively. After centrifugation, serum (2 μL) was loaded onto the tip of conductive polymer to form a dried serum spot. When the 5 μL methanol-water (1:1, v/v) extraction solvent was spiked onto the dried serum spot followed with +4.5 kV high voltage applied on the polymer tip, the extracted components will be ionized and carried into the MS system for direct metabolic profiling. FindingsThere were 51 metabolites discovered to be significantly changed in CRC serum compared to polyps. Combining these metabolites as the characteristic panel, the ideal diagnostic performance was achieved by Lasso regression model with the accuracy of 88.3%. InterpretationThis pilot study demonstrated the potential of CPSI-MS as a cost-effective tool in large-scale CRC screening in the high-risk population.

Iodide ions concentration sensing using polymer-tipped optical fiber

The concentration of iodide (I − ) ions was determined by a fluorescence quenching method; a polymer-tipped optical fiber (PTOF) was used as the sensing head. The polymer tip, made by a free-radical photopolymerization method, combined the advantages of high sensitivity of the tapered fiber with a flexible and simple fabrication process. A sol–gel encapsulated fluorescein, used as the fluorescence indicator, was dip coated on the surface of the PTOF. Experimental results indicate that the backscatter fluorescence intensity collected by PTOF is 9.60 times higher than that of the flat-cut fiber. When the I − ions concentration changed from 6 to 36 mM, the backscatter fluorescence intensity collected by PTOF decreased linearly with a response time of 2 s. We demonstrate a method that can detect remote ion concentration with high repeatability, with stability, and which is simple to carry out. This method can be used in applications such as chemical production and water quality monitoring.

High-throughput polymer tip-electrospray ionization mass spectrometry for enhanced detection of neopterin and biopterin in clinical urine samples.

Urinary biopterin (Bio) and neopterin (Neo) are important markers for clinical diagnosis of hyperphenylalaninemia. Herein, we developed a high-throughput analysis method based on electrospray ionization mass spectrometry (ESI-MS) with polymer tips for the rapid quantitative detection of Bio and Neo in clinical urine samples. Different polymer tips were investigated. It is found that the best detection sensitivity was achieved with hydrophobic polymer tip, ie, polyethylene tips. The high-throughput polymer tip-ESI-MS method allowed a rapid analysis speed at ~40seconds per sample. The limits of quantification (LOQ) (S/N≥10) for the detection of Bio and Neo were improved to be 5.0ng/mL. Acceptable relative standard deviation (RSD) values for Neo and Bio were measured to be 12.2% and 13.4% for direct measurement of Bio and Neo in raw urine samples, respectively. Furthermore, Bio and Neo were directly quantified from 18 clinical urine samples by presented method. The ratios of urinary Bio-to-Neo were analyzed for diagnosis of hyperphenylalaninemia. The results demonstrated that the present polymer tip-ESI-MS method is a promising strategy for the rapid analysis of clinical samples.

Polymer-spray mass spectrometric detection and quantitation of hydrophilic compounds and some narcotics.

High-throughput screening of biofluids is essential in monitoring concentration of a variety of drugs to determine their efficacy and toxicity. Organosiloxane polymers prepared by sol-gel chemistry as sample supports, and electrospray ionization emitters in a single material and as an alternative to paper substrates, is described in this study. Hydrophobic drugs and hydrophilic streptomycin were analyzed by polymer-spray mass spectrometry with an LTQ-Orbitrap mass spectrometer. Drug samples in urine (1-2 μL) were deposited on an OSX polymer, allowed to dry, then electrosprayed from the polymer tip into the mass spectrometer without sample pretreatment. The OSX polymers, whose polarity and porosity can be controlled, were prepared by sol-gel chemistry where methyl-substituted alkoxysilanes were hydrolyzed in the presence of a pore template and an acid catalyst. Five nanograms each of seven narcotic drugs were detected in <1min (relative standard deviation (RSD) of response <1% for each drug). Calibration curves of cocaine and streptomycin in urine were used to establish the performance of the polymer. For sample 1 (n=2), the mean recovery for cocaine was 81% with paper and 90% with polymer. Streptomycin is detected with polymer, not with paper; for samples 1 and 2 (n=3), mean recovery was 97% and 95%, respectively. Organosiloxane polymers achieve more sensitive analysis than paper, allowing for more accurate quantitation of both hydrophobic and hydrophilic drug compounds. The ability to tailor the polymer polarity and porosity allows for the synthesis of a wide range of polymers, and thus opens many possibilities for further development and applications.

Explosive sensing by using polymer tip on the end of optical fiber

The present study developed a new optical chemical sensor for detection of nitro-aromatic explosives in liquid phase. The method is based on the fluorescence quenching of conjugated polymer poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV). Polymer tip on the one end of single mode optical fiber was fabricated by photo polymerization reaction method. The tip was coated with MEH-PPV and used as sensor head to detect nitro-aromatic explosives. Compared to the normal end cut fiber this kind of sensor head can gather more fluorescence signal which indicate higher sensitivity. The sensing characteristics of the tip sensor head to dinitrobenzene (DNB) which is chemically similar to the common explosive TNT was studied. The optical sensor head coated with fluorescence indicator showed strong fluorescence quenching when exposed to DNB. A Stern-Volmer graph for DNB was constructed and showed that the range of concentration from 6mM to 30mM was linear and the response time of the sensor was within 1min.

Performance Testing of a Potential Replacement for Normetex Pump

Normetex® Model 15 scroll pump backed by metal bellows (MB) pump made by Senior Aerospace Inc. has been the preferred technology for use in tritium facilities world-wide. Normetex pumps are no longer available and identification of alternate pumps is required for performance and compatibility with tritium gas. Many of the pumps that could be used to meet the functional performance requirements (e.g. pressure and flow conditions) of the Normetex pump have features that include the use of polymers or oils and greases that are not directly compatible with tritium service. Though they are less desirable, alternative pumps may be used in tritium service with appropriate engineered controls to mitigate the impact of degraded organic compounds. These alternative pumps require characterization for potential application in tritium service. One pump that has been identified as a potential replacement for the Normetex pump in some tritium service applications is the Edwards nXDS15iC. A series of pump tests were completed using this pump as a candidate replacement pump. The purpose of the pump testing is two-fold: (1) obtain baseline vacuum pump characteristics for the replacement pump intended for use in tritium service; and (2) verify that low pressure hydrogen gas can be transported over various distances up to 92 meters (300 feet) by the candidate pump. A series of pump tests were performed at various configurations using hydrogen gas (no tritium) and nitrogen to ensure that this pump can meet the performance requirements. The Edwards pump meets the desired functional performance requirements, though there are other tradeoffs that must be considered. As for cost considerations, the Edwards scroll pump costs about ten (10) times less than a Normetex-equivalent scroll pump, which would significantly reduce initial start-up costs in a facility. However, the lifetime of the Edwards pump in a nearly pure tritium process stream is speculated to be only 3–6 months due to the polymer tip seals, whereas the all-metal Normetex pump can last for 5 years. Each application must determine whether the alternative pump considerations outweigh the cost differential. This paper summarizes the results of the tests that have been performed using various pump configurations.

Brownian Dynamics of Subunit Addition-Loss Kinetics and Thermodynamics in Linear Polymer Self-Assembly

The structure and free energy of multistranded linear polymer ends evolves as individual subunits are added and lost. Thus, the energetic state of the polymer end is not constant, as assembly theory has assumed. Here we utilize a Brownian dynamics approach to simulate the addition and loss of individual subunits at the polymer tip. Using the microtubule as a primary example, we examined how the structure of the polymer tip dictates the rate at which units are added to and lost from individual protofilaments. We find that freely diffusing subunits arrive less frequently to lagging protofilaments but bind more efficiently, such that there is no kinetic difference between leading and lagging protofilaments within a tapered tip. However, local structure at the nanoscale has up to an order-of-magnitude effect on the rate of addition. Thus, the kinetic on-rate constant, integrated across the microtubule tip (kon,MT), is an ensemble average of the varying individual protofilament on-rate constants (kon,PF). Our findings have implications for both catastrophe and rescue of the dynamic microtubule end, and provide a subnanoscale framework for understanding the mechanism of action of microtubule-associated proteins and microtubule-directed drugs. Although we utilize the specific example of the microtubule here, the findings are applicable to multistranded polymers generally.

Fabrication of 15 nm curvature radius polymer tip probe on an optical fiber via two-photon polymerization and O2-plasma ashing

Polymer tips with 15 nm curvature radius apexes that are capable of scanning the surface of a sample have been fabricated on the surface of an optical fiber using two-photon photopolymerization (TPP) and O2-plasma ashing with a SCR500 resin. First, the parent conical polymer tip with a 125 nm curvature radius apex was fabricated via TPP using a continuous scanning method and the accumulation of circular layers. Next, the tip was sharpened using an O2-plasma ashing process with high reproducibility. As a result, the apex radius of curvature had a maximum reduction to 15 nm. In order to evaluate the performance of the 15 nm curvature radius polymer tip, a 30 nm thick gold layer with holes of 250 nm radius and a single layer of polystyrene beads with a 350 nm radius were imaged using a tuning-fork-based atomic force microscope. The topographic images obtained by the 15 nm polymer tip were improved in width and depth compared with those obtained by the 125 nm polymer tip due to the reduction of the imaging artifacts. This method can also be commonly used to reduce the radius of curvature of the polymer tip in order to achieve more accurate imaging.

Fabrication of sharp-needled conical polymer tip on the cross-section of optical fiber via two-photon polymerization for tuning-fork-based atomic force microscopy

Aiming at the use in tuning-fork-based atomic force microscopy (TF-based AFM), we propose and demonstrate fabrication methods of polymer tips on the cross-section of optical fibers by two-photon polymerization (TPP) using SCR500 resin. This method can be applied to any optical fibers or other bases regardless of the type. The specified polymer tips are fabricated with high reproducibility by this method. First, a conical polymer tip was fabricated via a continuous-scanning method and layer-by-layer accumulation of circular layers which reduce to a point along with the growth from the cross-section of optical fibers, by using a five-axis optical fiber mount combined with a two-photon nanofabrication system. A sharp-needled conical polymer tip of a 45nm radius of curvature was fabricated with attachment of four voxels. These voxels were fabricated by the gradually-decreasing-exposure-time method on the apex of the simple conical tip. We have also designed and fabricated a triple-tapered polymer tip to demonstrate the feasibility of fabricating various tip shapes by the TPP method for the TF-based AFM. Moreover, the photoluminous polymer tip was fabricated using ORMOCER mixed with quantum dots. The sharp-needled polymer tip was utilized for the TF-based AFM using an optical fiber probe to investigate the performance of the polymer tip fabricated by the TPP method, and we have obtained a topographic image of a pitted sample. Finally, the near-field image of the 30-nm-thick gold layer with holes of 250-nm-radius was successfully obtained by the aluminum-coated NSOM probe fabricated on the TPP conical polymer tip with a radius of curvature of 45nm in NSOM system.

A Mathematical Model for Force Generation at the Kinetochore-Microtubule Interface

In this paper we construct and analyze a mathematical model for kinetochore (Kt) motors operating at the chromosome/microtubule interface. Motor dynamics are modeled using a jump-diffusion process that incorporates biased diffusion due to the binding of microtubules (MTs) by Kt binder elements and thermal ratchet forces that arise when the polymer grows against the Kt plate. The resulting force-velocity relationships are nonlinear and depend on the strength of MT binding at Kts, as well as the spatial distribution of binders and of MT rate-altering enzymes inside the Kt. In the case when Kt binders are weakly bound and spaced with the same period as the MT binding sites, the numerical results for the motor force-velocity relation and breaking loads are in complete agreement with our approximate analytic solutions. We show that in this limit motor velocity depends directly on the balance of polymer tip polymerization/depolymerization rates and is fairly insensitive to load variations. In the strong binding...

Fabry-Perot refractometer based on an end-of-fiber polymer tip

A micrometric Fabry-Perot refractometer based on an end-of-fiber polymer tip is proposed. The fiber tip, with a length of 36 mum, was fabricated by self-guiding photopolymerization. The two-wave interferometric operation was achieved by combining the light waves generated at the interface between the single-mode fiber and the polymer tip, and at the fiber tip end (Fresnel reflection). The Fabry-Perot interferometer is coherence addressed and heterodyne interrogated, resulting into a liquid refractive index resolution of approximately 7.5x10(-4).

Tailoring the geometry of polymer tips on the end of optical fibers via control of physico-chemical parameters

This paper deals with the improvement of polymer microlenses at the extremity of an optical fiber. The process reported previously involves a spatially controlled light-induced polymerization within a drop of liquid photopolymerizable formulation deposited on the end of a cleaved fiber. The process is of highest interest for applications in optical connecting and optical fiber sensor since it is fast, highly flexible (curvature radii ranges from 0.2 to 200 μm) and does not require expensive equipment. In particular, the spatial extend of the photopolymerization was demonstrated to be highly dependent on physico-chemical parameters of the formulation. The influence of parameters that govern the photopolymerization reaction and light propagation in the photopolymerizable medium such as irradiation time, light power, oxygen quenching and dye absorption, were studied in order to control the final properties of the polymer tip. The present study allowed selecting the synthesis parameters leading to well-controlled geometrical structures. From a fundamental point of view, this study appeared to be an interesting means to investigate the photostructuration of polymers at the micro- and nanoscales.

Fabrication of CdSe–ZnS nanocrystal-based local fluorescent aperture probes by active polymerization of photosensitive epoxy

We report the fabrication of a nanocrystal (NC) doped polymer tip at the end of a single-mode optical fiber with active polymerization technique. The tip is created by immersing the fiber in a photosensitive epoxy precursor containing colloidal CdSe–ZnS NCs and polymerizing the epoxy using laser light introduced through the fiber. The laser power was found to have a strong influence on the tip height and shape. As the laser beam progressed from the fiber end, the power was reduced by conversion and absorption, resulting in a cone-shaped tip. The shape of the extreme end of the tip was sensitive to the transmitted beam pattern, indicating that the shape of the tip is independent of the substrate fiber. A blue shift and reduction in decay time suggest that the emission properties of the NCs are affected by immobilization in the epoxy, possibly because of oxidation at the NC surface.

Polymer tips for application of atomic force microscopy

Abstract A hydrophobic polymer tip for atomic force microscopy has been fabricated by two-photon adsorbed photopolymerization techniques and has been applied for the high resolution imaging of a hydrophilic metal surface. Using optimized photopolymerization conditions, we have succeeded in fabricating sub-100-nm sized polymer tips. This fabricating resolution of two-photon adsorbed photopolymerization is also confirmed by other supporting experiments. The imaging results show that the capillary-force-induced image distortion can be successfully removed by applying a pure hydrophobic polymer tip with a lateral resolution better than 5 nm, which is difficult to achieve with a commercial tip without any environmental control.

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.