1,720,975 research outputs found
Design, fabrication, and penetration assessment of polymeric hollow microneedles with different geometries
No full textHollow microneedles (HMNs) are minimally invasive needle-like microfeatures usually arranged in arrays designed for drug delivery and body fluid collection in a painless manner. In a recent work, we demonstrated a novel methodology to mass produce hollow polymer microneedles at a low cost. This methodology combines ultrashort pulse laser ablation to create inverse needle shapes in moulds and replication through polymer injection moulding. For a HMN to be functional, it should effectively pierce the skin at a low force and enable fluidic passage through the skin without leakage. This study investigates the impact of different laser scanning strategies on the cavity morphology and analyses how the various geometrical characteristics of the needle influence the penetration efficacy. To assess the penetration behaviour of the replicated HMNs, a combination of agarose gel and Parafilm (R) is employed as an in vitro testing platform. Furthermore, a correlation between HMN geometry, penetration performance, and modification of polymer material and holding pressure during injection moulding is established. The results indicate that a certain needle length is essential for effective penetration. Moreover, minimising the tip area, a factor significantly affecting penetration force, can be achieved by increasing the eccentricity of the scan-free area and expanding the scanning diameter. However, it is important to consider other functional needle features such as the ridge height or full lumen, which come at a cost to the tip sharpness. This work highlights the multiple interactions between the scanning strategy, the injection moulding process parameters, the needle geometry, and the penetration force. This study provides insights into optimization of the HMN design and the fabrication for enhanced penetration efficacy of functional injection-moulded polymeric HMNs.Funding
This work was funded by the KU Leuven Interdisciplinary Network project IDN/20/011 MIRACLE: Autonomous microfuidic patch for plasmid-based vaccine, as well as the Fonds Wetenschappelijk Onderzoek (FWO)–Vlaanderen SBO project S003923N and SB fellowship 1S31022N. The FWO large infrastructure I013518N project is acknowledged for their fnancial support of the X-ray infrastructure.
Acknowledgements
The authors would like to thank Olivier Malek from Sirris (department of Precision Manufacturing) for the laser ablation of the microneedle cavities. The KU Leuven XCT Core facility is acknowledged for the 3D image acquisition and quantitative postprocessing tools (https://xct.kuleuven.be/)
Predicting the replication fidelity of injection molded solid polymer microneedles
No full textsponsorship: This work was funded by the KU Leuven Interdisciplinary Network project IDN/20/011 -MIRACLE: Autonomous microfluidic patch for plasmid-based vaccine. (KU Leuven Interdisciplinary Network project IDN/20/011 -MIRACLE: Autonomous microfluidic patch for plasmid-based vaccine)status: Publishe
Comparing the Replication Fidelity of Solid Microneedles Using Injection Compression Moulding and Conventional Injection Moulding
No full textPolymer surfaces are increasingly being functionalized with micro- and nano- surface features using mass replication methods such as injection moulding. An example of these are microneedle arrays, which contain needle-like microscopic structures, which facilitate drug or vaccine delivery in a minimally invasive way. In this study, the replication fidelity of two types of solid polycarbonate microneedles was investigated using injection compression moulding and conventional injection moulding. Using a full factorial design of experiments for the injection moulding process, it was found that the volumetric injection rate had the largest positive effect on the replication fidelity. The mould temperature and holding pressure were also found to have a positive effect, while the effect of the melt temperature was found to be insignificant for the considered temperature range. For the injection compression moulding process, it was found that a larger compression stroke resulted in a better replication fidelity. A comparison between the replication fidelity for the injection moulding and injection compression moulding indicated that the injection compression moulding process resulted in a higher and more uniform replication fidelity. Using finite element flow simulations, a higher and more evenly distributed cavity pressure was observed compared to the conventional injection moulding process
Controlling the geometry of laser ablated microneedle cavities in different mould materials and assessing the replication fidelity within polymer injection moulding
No full textMicroneedle arrays are minimally invasive devices which enable self-administration of drugs in a straightforward and efficient way. Recently, a low-cost mass production method to produce solid polymer microneedles using laser ablated moulds in an injection moulding process has been developed. In this context, it is key to understand how the geometry of the microneedle cavities can be changed and what parameters affect the replication fidelity during injection moulding. In this study, two laser scanning parameters, being the programmed base diameter and the number of layers were varied in four levels and their effects on the geometry of the microneedle cavities were evaluated in tool steel, copper alloy, and aluminium alloy inserts. Afterwards, the microneedle cavities were replicated in polypropylene and polycarbonate using injection moulding. The study showed how the depth and base diameter of the microneedle cavity can be changed by varying laser scanning parameters. Moreover, the moulds in the three materials exhibited different microneedle cavity shapes and dimensions, due to differences in material properties. As to the injection moulding process, strong linear relationships were found between the aspect ratio of the microneedle cavities and the replicated thermoplastic microneedles, where a higher aspect ratio resulted in a lower replication. The replication fidelity for the polypropylene microneedles was in all cases higher compared to the polycarbonate needles. Between the three mould materials, a comparable replication fidelity was found for tool steel and copper alloy and a lower replication for the aluminium alloy, due to differences in thermal and wetting properties.sponsorship: This work was supported by internal funding from KU Leuven Campus Diepenbeek, Belgium. (KU Leuven Campus Diepenbeek, Belgium)status: Publishe
Producing Hollow Polymer Microneedles Using Laser Ablated Molds in an Injection Molding Process
No full textsponsorship: KU Leuven Interdisciplinary Network (Project IDN/20/011-MIRACLE; Funder ID: 10.13039/501100004040). (KU Leuven Interdisciplinary Network|IDN/20/011-MIRACLE)status: Publishe
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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