Dynamically variable focal length microlens by microfluidic and electroactive polymer approaches

This research is on a development of a variable focusing microlens system. The studies of modern researchers have thrown new light on this subject, which has aroused intense interest in making tunable focusing microlenses. The most well-known methods are liquid crystal and electrowetting. Both methods require electrodes immersed in the electrolyte solution, causing severe optical distortion, and require complicated fabrication processes. Few attempts have thus far been developed to make variable focusing lens using other approaches. However, two novel actuation mechanisms have been developed in this work for generating significant forces to change the physical dimensions of an elastic polymeric lens structure to control the focal length. The two proposed actuation mechanisms are: (1) the microfluidic and (2) the Electro-Active Polymer (EAP) actuations. By pneumatically regulating the pressure of the microfluidic chamber, the elastic lens can be deformed, causing the changes in the focal length. EAP is another method to transfer electrical energy to mechanical deformation. This energy transformation causes the deflection on the lens and induces its focal plane to be shifted. For the microfluidic lens system, a novel PDMS to PDMS casting process to fabricate 3D convex elastic microlens diaphragm is developed. This new fabrication technique has a potential for producing low-cost elastic microlens arrays. Microlenses, with a diameter of 600∼1400 μm, are fabricated using this fabrication technique. The curvature changes of the microlens were from 1210μm to 3238μm. With this wide range of curvature changes, one can control the back focal length from 3.82 mm to 10.64 mm, and the numerical aperture from 0.09 to 0.24. The numerical aperture of this optical device can then reach 0.24, about 4 times that of a conventional planar diaphragm (NA = 0.05). Moreover, a new “two-step copolymerization” technique has been developed to fabricate an elastic silicone-based gradient refractive index (GRIN) lens. This is a flat lens with a gradient refractive index distribution within the lens structure. Moreover, this GRIN lens is elastic, so it is deformable with high elongation under mechanical stresses. Finally, this lens is made by a dielectric material, and can be integrated easily into an EAP actuator, generating enough mechanical force to cause the deflection on the GRIN lens and induce a shift in focal length. The characteristics of GRIN lenses and EAP actuation have been studied in this work. It appears that this is the first reported work proposing a dynamically tunable focusing GRIN lens with an EAP actuation. Further research needs to be carrying out for optimizing the proposed approach for its desired application

Cytokine Profile in Plasma Extracellular Vesicles of Parkinson's Disease and the Association with Cognitive Function

Plasma extracellular vesicles (EVs) containing various molecules, including cytokines, can reflect the intracellular condition and participate in cell-to-cell signaling, thus emerging as biomarkers for Parkinson’s disease (PD). Inflammation may be a crucial risk factor for PD development and progression. The present study investigated the role of plasma EV cytokines as the biomarkers of PD. This cross-sectional study recruited 113 patients with PD, with mild to moderate stage disease, and 48 controls. Plasma EVs were isolated, and the levels of cytokines, including pro-interleukin (IL)-1β, IL-6, IL-10, tumor necrosis factor (TNF)-α, and transforming growth factor (TGF)-β1, were evaluated. Patients with PD had significantly increased plasma EV pro-IL-1β and TNF-α levels compared with controls after adjustment for age and sex. Despite the lack of a significant association between plasma EV cytokines and motor symptom severity in patients with PD, cognitive dysfunction severity, assessed using the Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment, was significantly associated with plasma EV pro-IL-1β, IL-6, IL-10, and TNF-α levels. This association was PD specific and not found in controls. Furthermore, patients with PD cognitive deficit (MMSE < 26) exhibited a distinguished EV cytokine profile compared to those without cognitive deficit. The findings support the concept of inflammatory pathogenesis in the development and progression of PD and indicate that plasma EV cytokines may serve as PD biomarkers in future

Biomechanical comparison of lumbar spine instability between laminectomy and bilateral laminotomy for spinal stenosis syndrome – an experimental study in porcine model

<p>Abstract</p> <p>Background</p> <p>The association of lumbar spine instability between laminectomy and laminotomy has been clinically studied, but the corresponding <it>in vitro </it>biomechanical studies have not been reported. We investigated the hypothesis that the integrity of the posterior complex (spinous process-interspinous ligament-spinous process) plays an important role on the postoperative spinal stability in decompressive surgery.</p> <p>Methods</p> <p>Eight porcine lumbar spine specimens were studied. Each specimen was tested intact and after two decompression procedures. All posterior components were preserved in Group A (Intact). In Group B (Bilateral laminotomy), the inferior margin of L4 lamina and superior margin of L5 lamina were removed, but the L4–L5 supraspinous ligament was preserved. Fenestrations were made on both sides. In Group C (Laminectomy) the lamina and spinous processes of lower L4 and upper L5 were removed. Ligamentum flavum and supraspinous ligament of L4–L5 were removed. A hydraulic testing machine was used to generate an increasing moment up to 8400 N-mm in flexion and extension. Intervertebral displacement at decompressive level L4–L5 was measured by extensometer</p> <p>Results</p> <p>The results indicated that, under extension motion, intervertebral displacement between the specimen in intact form and at two different decompression levels did not significantly differ (<it>P </it>> 0.05). However, under flexion motion, intervertebral displacement of the laminectomy specimens at decompression level L4–L5 was statistically greater than in intact or bilateral laminotomy specimens (<it>P </it>= 0.0000963 and <it>P </it>= 0.000418, respectively). No difference was found between intact and bilateral laminotomy groups. (<it>P </it>> 0.05).</p> <p>Conclusion</p> <p>We concluded that a lumbar spine with posterior complex integrity is less likely to develop segment instability than a lumbar spine with a destroyed anchoring point for supraspinous ligament.</p

What is Needed for Future 3D Printing from Maker’S Viewpoints

This study focused on investigating makers’ opinions about current 3D printing technology to foster the development and use of 3D printing technologies in Taiwan. 3D printing has revolutionized the manufacturing industries as it provided a highly flexible, customizable way of small-quantity production at low cost. Its popularity among general users, however, encountered difficulties such as high requirements in skills, less user-friendliness, lack of practicality, low reliability, etc. Makers, a special group of customers of 3D printers are familiar with problems of this technology as they shared experience on the Internet, started collaborative manufacturing with open sources and turned their DIY activities into E-business. The study utilized questionnaires in the makers’ space to obtain the background of this special group of customers, their viewpoints regarding important features to consider for purchasing a 3D printer, and difficulties and solutions in propagation of 3D printing. The results demonstrated that makers were a group of extrovert and intuitive thinkers in terms of MBTI personalities and treasured printing precision (surface quality), stability (long tuning period) and easy maintenance as most attractive factors to customers. From their viewpoints, difficulties in use, customers’ low interests, and lack of practicality of its products were rated top 3 problems for 3D printing. However, school education, propagation of makers’ space and development of ease-to-use 3D software may help its popularity. The results of this study may help 3D printer manufacturers and 3D printing service providers to better understand their customers’ behaviors, based on which better 3D printing services and 3D printers can be developed to improve their business

Optimisation- based time slot assignment and synchronisation for TDMA MAC in industrial wireless sensor network

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/166209/1/cmu2bf02232.pd

Hypothermic manipulation of bone cement can extend the handling time during vertebroplasty

BACKGROUND: Polymethylmethacrylate (PMMA) is commonly used for clinical applications. However, the short handling time increases the probability of a surgeon missing the crucial period in which the cement maintains its ideal viscosity for a successful injection. The aim of this article was to illustrate the effects a reduction in temperature would have on the cement handling time during percutaneous vertebroplasty. METHODS: The injectability of bone cement was assessed using a cement compressor. By twisting the compressor, the piston transmits its axial load to the plunger, which then pumps the bone cement out. The experiments were categorized based on the different types of hypothermic manipulation that were used. In group I (room temperature, sham group), the syringes were kept at 22°C after mixing the bone cement. In group 2 (precooling the bone cement and the container), the PMMA powder and liquid, as well as the beaker, spatula, and syringe, were stored in the refrigerator (4°C) overnight before mixing. In group 3 (ice bath cooling), the syringes were immediately submerged in ice water after mixing the bone cement at room temperature. RESULTS: The average liquid time, paste time, and handling time were 5.1 ± 0.7, 3.4 ± 0.3, and 8.5 ± 0.8 min, respectively, for group 1; 9.4 ± 1.1, 5.8 ± 0.5, and 15.2 ± 1.2 min, respectively, for group 2; and 83.8 ± 5.2, 28.8 ± 6.9, and 112.5 ± 11.3 min, respectively, for group 3. The liquid and paste times could be increased through different cooling methods. In addition, the liquid time (i.e. waiting time) for ice bath cooling was longer than for that of the precooling method (p < 0.05). CONCLUSIONS: Both precooling (i.e. lowering the initial temperature) and ice bath cooling (i.e. lowering the surrounding temperature) can effectively slow polymerization. Precooling is easy for clinical applications, while ice bath cooling might be more suitable for multiple-level vertebroplasty. Clinicians can take advantage of the improved injectability without any increased cost

Phase-controlled vibrational laser percussion drilling

In this study, a phase-controlled vibration was applied to a laser percussion drilling process to improve the depth of penetration. To investigate the effects of phase-controlled vibration on the depth of penetration, a novel method that controls the phase offset between the accelerating motion and the emission of the laser beam was developed. The method is based on coaxial sensing of the working surface using a photodiode, coupled with microcontroller control of the drilling laser operation. Through real-time optical signal acquisition and analysis of laser machining processes, correlations between the accelerating motion and the emission of the laser beam were simultaneously obtained. All of the processing work was performed in air at standard atmospheric conditions, and gas assist was not used. This study showed that the application of phase-controlled vibration improved the depth of penetration in laser percussion machining and can contribute to the development of precision drilling in the industry

Pullout strength of pedicle screws with cement augmentation in severe osteoporosis: A comparative study between cannulated screws with cement injection and solid screws with cement pre-filling

<p>Abstract</p> <p>Background</p> <p>Pedicle screws with PMMA cement augmentation have been shown to significantly improve the fixation strength in a severely osteoporotic spine. However, the efficacy of screw fixation for different cement augmentation techniques, namely solid screws with retrograde cement pre-filling versus cannulated screws with cement injection through perforation, remains unknown. This study aimed to determine the difference in pullout strength between conical and cylindrical screws based on the aforementioned cement augmentation techniques. The potential loss of fixation upon partial screw removal after screw insertion was also examined.</p> <p>Method</p> <p>The Taguchi method with an L₈array was employed to determine the significance of design factors. Conical and cylindrical pedicle screws with solid or cannulated designs were installed using two different screw augmentation techniques: solid screws with retrograde cement pre-filling and cannulated screws with cement injection through perforation. Uniform synthetic bones (test block) simulating severe osteoporosis were used to provide a platform for each screw design and cement augmentation technique. Pedicle screws at full insertion and after a 360-degree back-out from full insertion were then tested for axial pullout failure using a mechanical testing machine.</p> <p>Results</p> <p>The results revealed the following 1) Regardless of the screw outer geometry (conical or cylindrical), solid screws with retrograde cement pre-filling exhibited significantly higher pullout strength than did cannulated screws with cement injection through perforation (<it>p </it>= 0.0129 for conical screws; <it>p </it>= 0.005 for cylindrical screws). 2) For a given cement augmentation technique (screws without cement augmentation, cannulated screws with cement injection or solid screws with cement pre-filling), no significant difference in pullout strength was found between conical and cylindrical screws (<it>p ></it>0.05). 3) Cement infiltration into the open cell of the test block led to the formation of a cement/bone composite structure. Observations of the failed specimens indicated that failure occurred at the composite/bone interface, whereas the composite remained well bonded to the screws. This result implies that the screw/composite interfacial strength was much higher than the composite/bone interfacial strength. 4) The back-out of the screw by 360 degrees from full insertion did not decrease the pullout strength in any of the studied cases. 5) Generally, larger standard deviations were found for the screw back-out cases, implying that the results of full insertion cases are more repeatable than those of the back-out cases.</p> <p>Conclusions</p> <p>Solid screws with retrograde cement pre-filling offer improved initial fixation strength when compared to that of cannulated screws with cement injection through perforation for both the conically and cylindrically shaped screw. Our results also suggest that the fixation screws can be backed out by 360 degrees for intra-operative adjustment without the loss of fixation strength.</p

Association of DRD4 uVNTR and TP53 codon 72 polymorphisms with schizophrenia: a case-control study

<p>Abstract</p> <p>Background</p> <p>The tumour supressor gene TP53 is thought to be involved in neural apoptosis. The polymorphism at codon 72 in TP53 and the long form variants of the upstream variable number of tandem repeats (uVNTR) polymorphism in the dopamine D4 receptor (DRD4) gene are reported to confer susceptibility to schizophrenia.</p> <p>Methods</p> <p>We recruited 934 patients with schizophrenia and 433 healthy individuals, and genotyped the locus of the TP53 codon 72 and DRD4 uVNTR polymorphisms by combining the polymerase chain reaction-restriction fragment length polymorphism method (PCR-RFLP) with direct sequencing.</p> <p>Results</p> <p>No significant differences were found in the frequency of the genotype of the TP53 codon72 polymorphism between patients with schizophrenia and their controls. However, the long form alleles (≥ 5 repeats) of the DRD4 uVNTR polymorphism were more frequent in patients with schizophrenia than in controls (p = 0.001). Hence, this class of alleles might be a risk factor for enhanced vulnerability to schizophrenia (odds ratio = 3.189, 95% confidence interval = 1.535-6.622). In the logistic regression analysis, the long form variants of the DRD4 polymorphism did predict schizophrenia after the contributions of the age and gender of the subjects were included (p = 0.036, OR = 2.319), but the CC and GG genotypes of the codon 72 polymorphism of TP53 did not.</p> <p>Conclusions</p> <p>The long form variants of the uVNTR polymorphism in DRD4 were associated with schizophrenia, in a manner that was independent of the TP53 codon 72 polymorphism. In addition, given that the genetic effect of the TP53 codon 72 polymorphism on the risk of developing schizophrenia was very small, this polymorphism is unlikely to be associated with schizophrenia. The roles that other single nucleotide polymorphisms (SNPs) in the TP53 gene or in other apoptosis-related genes play in the synaptic dysfunction involved in the pathogenesis of schizophrenia should be investigated.</p