Needle Geometry Research Articles

Scalable electrospinning using a desktop, high throughput, self-contained system

Electrospinning is a specialized processing technique for the formation of submicron diameter fibers of polymeric and ceramic materials using an electrostatic field. The process has multiple advantages over other nano- and micro- fiber synthesis methods; however, generally suffers from very low fabrication speeds, making it undesirable for scalability. This work assesses the performance of a needle-less, self-contained, high throughput electrospinning system. It further compares the fiber fabrication rates obtained versus two single needle setups with different collectors: (i) a conventional single needle and flat plate geometry, and (ii) a single needle with a rotating collector geometry. Polyvinylpyrrolidone (PVP) in ethanol was used as the model material. The fabrication rate of the high throughput system “HTES” was measured at about 2.6 g/h and was about 15 times that collected of the flat plate. Comparing it to other systems reported in the literature also proved it to be a viable option for high throughput, lab scale electrospinning.

Impact of Needle Design and Suture Gauge on Tissue Tearing During Skin Suturing: A Comparative Analysis.

Surgeons face numerous choices in selecting sutures for skin closure, with potential adverse effects such as tissue tearing. To investigate the influence of needle design and suture gauge on tissue tearing during suturing procedures. The authors tested the tear-through force in Newtons for 3 needle types and 3 suture gauges using an artificial skin model and a professional-grade tensiometer. Suture material was secured into the skin model, and force was applied to the suture at a constant rate, resulting in tearing. Force-displacement and force-time curves were generated. Evaluation included conventional cutting (PC-3), reverse cutting (PS-3), and taper point (BB) needles with a 5-0 polypropylene suture. In addition, nylon sutures with a reverse cutting needle (PS-2) were tested at 3 suture gauges (5-0, 4-0, 3-0). The mean tear-through forces for PC-3, PS-3, and BB were 3.26 N, 3.75 N, and 4.07 N, respectively. For the 5-0, 4-0, and 3-0 nylon sutures, the mean tear-through forces were 3.44 N, 3.81 N, and 4.04 N, respectively. Statistical analysis revealed a significant impact of suture gauge size (p < .001) and needle geometry (p < .001) on tear-through force. Larger suture diameter and taper needles minimize tissue tearing.

3D-Printed Latticed Microneedle Array Patches for Tunable and Versatile Intradermal Delivery.

Using high-resolution 3D printing, a novel class of microneedle array patches (MAPs) is introduced, called latticed MAPs (L-MAPs). Unlike most MAPs which are composed of either solid structures or hollow needles, L-MAPs incorporate tapered struts that form hollow cells capable of trapping liquid droplets. The latticestructures can also be coated with traditional viscous coating formulations, enabling both liquid- and solid-state cargo delivery, on a single patch. Here, a library of 43 L-MAP designs is generated and in-silico modeling is used to down-select optimal geometries for further characterization. Compared to traditionally molded and solid-coated MAPs, L-MAPs can load more cargo with fewer needles per patch, enhancing cargo loading and drug delivery capabilities. Further, L-MAP cargo release kinetics into the skin can be tuned based on formulation and needle geometry. In this work, the utility of L-MAPs as a platform is demonstrated for the delivery of small molecules, mRNA lipid nanoparticles, and solid-state ovalbumin protein. In addition, the production of programmable L-MAPs is demonstrated with tunablecargo release profiles, enabled by combining needle geometries on a single patch.

52703 Correlation of Needle Geometry and Suture’s Ability to Tear Through an Artificial Skin Model

52703 Correlation of Needle Geometry and Suture’s Ability to Tear Through an Artificial Skin Model

Design of poly(vinyl pyrrolidone) and poly(ethylene glycol) microneedle arrays for delivering glycosaminoglycan, chondroitin sulfate, and hyaluronic acid

Osteoarthritis (OA) is a prevalent joint disorder characterized by cartilage and bone degradation. Medical therapies like glucosaminoglycan (GAG), chondroitin sulfate (CS), and hyaluronic acid (HA) aim to preserve joint function and reduce inflammation but may cause side effects when administered orally or via injection. Microneedle arrays (MNAs) offer a localized drug delivery method that reduces side effects. Thus, this study aims to demonstrate the feasibility of delivering GAG, CS, and HA using microneedles in vitro. An optimal needle geometry is crucial for the successful application of MNA. To address this, here we employ a multi-objective optimization framework using the non-dominated sorting genetic algorithm II (NSGA-II) to determine the ideal MNA design, focusing on preventing needle failure. Then, a three-step fabrication approach is followed to fabricate the MNAs. First, the master (male) molds are fabricated from poly(methyl methacrylate) using mechanical micromachining based on optimized needle geometry. Second, a micro-molding with Polydimethylsiloxane (PDMS) is used for the fabrication of production (female) molds. In the last step, the MNAs were fabricated by microcasting the hydrogels using the production molds. Light microscopy (LIMI) confirms the accuracy of the MNAs manufactured, and in vitro skin insertion tests demonstrate failure-free needle insertion. Subsequently, we confirmed the biocompatibility of MNAs by evaluating their impact on the L929 fibroblast cell line, human chondrocytes, and osteoblasts.

Experimental Study of Needle Insertion into Gerbil Tympanic Membrane.

The perforation characteristics and fracture-related mechanical properties of the tympanic membrane (TM) greatly affect surgical procedures like myringotomy and tympanostomy performed on the middle ear. We analyzed the most important features of the gerbil TM perforation using an experimental approach that was based on force measurement during a 2-cycle needle insertion/extraction process. Fracture energy, friction energy, strain energy, and hysteresis loss were taken into consideration for the analysis of the different stages of needle insertion and extraction. The results demonstrated that (1) although the TM shows viscoelastic behavior, the contribution of hysteresis loss was negligible compared to other irreversible dissipated energy components (i.e., fracture energy and friction energy). (2) The TM puncture force did not substantially change during the first hours after animal death, but interestingly, it increased after 1week due to the drying effects of soft tissue. (3) The needle geometry affected the crack length and the most important features of the force-displacement plot for the needle insertion process (puncture force, puncture displacement, and jump-in force) increased with increasing needle diameter, whereas the insertion velocity only changed the puncture and jump-in forces (both increased with increasing insertion velocity) and did not have a noticeable effect on the puncture displacement. (4) The fracture toughness of the gerbil TM was almost independent of the needle geometry and was found to be around 0.33 0.10kJ/m2.

Influence of needle geometry on mechanical properties of 3D printed microneedle arrays

Influence of needle geometry on mechanical properties of 3D printed microneedle arrays

Coaxial extrusion bioprinting of hydrazone crosslinked POEGMA hydrogels: Optimizing needle geometry to achieve improved print quality

Facilitating effective mixing of two or more functional polymers remains a challenge when translating in situ-crosslinking click chemistry hydrogels to extrusion bioprinting applications. In this work, the conventional flush coaxial needle was modified to introduce a mixing region to promote the mixing of low-viscosity hydrazide and aldehyde-functionalized poly (oligoethylene glycol methacrylate) (POEGMA) polymers that form dynamic hydrazone bonds upon crosslinking. The inclusion of the mixing region significantly reduced the spreading of the printed fibers and improved the homogeneity of both the printed hydrogel and the encapsulated cells. Computational modeling based on non-Newtonian fluid behavior in the mixing zone confirmed that increasing the length of the mixing zone improved the mixing efficiency, a finding supported by experimental printing results. As such, particularly with less viscous bioinks like the oligomeric hydrazide/aldehyde-functionalized POEGMA polymers used herein, the inclusion of this mixing region provides an effective means of printing functional precursor polymers that can chemically crosslink upon mixing.

Theoretical Puncture Mechanics of Soft Compressible Solids

Abstract Accurate prediction of the force required to puncture a soft material is critical in many fields like medical technology, food processing, and manufacturing. However, such a prediction strongly depends on our understanding of the complex nonlinear behavior of the material subject to deep indentation and complex failure mechanisms. Only recently, we developed theories capable of correlating puncture force with material properties and needle geometry. However, such models are based on simplifications that seldom limit their applicability to real cases. One common assumption is the incompressibility of the cut material, albeit no material is truly incompressible. In this article, we propose a simple model that accounts for linearly elastic compressibility, and its interplay with toughness, stiffness, and elastic strain stiffening. Confirming previous theories and experiments, materials having high toughness and low modulus exhibit the highest dimensionless puncture resistance at a given needle radius. Surprisingly, in these conditions, we observe that incompressible materials exhibit the lowest puncture resistance, where volumetric compressibility can create an additional (strain) energy barrier to puncture. Our model provides a valuable tool to assess the puncture resistance of soft compressible materials and suggests new design strategies for sharp needles and puncture-resistant materials.

Microstructure of macrointerfaces in shape-memory alloys

Shape-memory alloys exhibit a rich microstructure, characterized by large regions containing relatively regular laminates mixing different martensitic variants. Macrointerfaces separate these regions, and are often composed of arrays of needle-shaped martensitic domains. We formulate a model for the geometry of arrays of needles and present numerical simulations, appropriate for two compound twinned variants of martensite in a plane stress setting. One important ingredient is a new class of polyconvex energy densities with cubic symmetry, that is able to reproduce the austenitic elastic constants of the relevant materials. The energy-minimizing needle geometry is determined with tools from shape optimization. Our main finding is the “transparency effect”, which characterizes the effect of needles on domain boundaries located in front of their tip. Our numerical results are in good agreement with experimental observations.

Patient-specific cylinder templates for hybrid interstitial vaginal brachytherapy: Feasibility of automated 3-D design, 3D printing, and dosimetric outlook

Delivering highly conformal treatment plans for high-dose rate vaginal brachytherapy using commercially available applicators can be challenging. A partially automated workflow is presented for the in-house modeling and 3D printing of patient-specific cylindrical templates (PSCTs), which facilitate placement of flexible intracavitary and interstitial needles. To demonstrate feasibility, we compare PSCT treatment plans to retrospective interstitial brachytherapy plans delivered at our center. PSCTs derived from these plans were 3D printed to test the validity of the auto-design process. To facilitate clinical implementation, we validated the steam sterilization compatibility of PSCTs printed using polyetheretherketone (PEEK). Plans for ten patients treated using a combination of vaginal cylinder and interstitial needles were compared to PSCT-based plans created for the same patient. DVH parameters for the HRCTV (V100, V150, V200, D90) and OARs (D2 cm3) were evaluated, as well as the number of needles used and the total interstitial length. Each planned PSCT was printed and compared to the intended needle geometry. 3D printed models were sterilization validated by an independent contractor for an autoclave protocol. PSCT plans demonstrated advantages over template based perineal BT in reducing the total interstitial needle length required while preserving or improving HRCTV and OAR dosimetry. All printed PSCTs matched planned geometry. PSCTs stand to be an alternative to current HDR-BT templates/applicators for patients with vaginal and locally recurrent endometrial cancers. Clinically equivalent or improved treatment plans can be created and devices to deliver these plans can be accurately printed and sterilized.

Molecular dynamics simulation on fabrication of chiral nanoneedle by optical vortex

We have successfully generated tantalum chiral nanoneedles in silico using three-dimensional molecular dynamics simulation to calculate the time evolution of the motion of atoms. Since current computer capabilities do not allow this nanostructure formation to be calculated at the electron level, the interaction between the optical vortex and tantalum atoms is approximated by a pseudo electric force field, which is proportional to the electric field. The embedded atom method potential “2013_eam.alloy” is used for the interatomic forces between tantalum atoms. The dependence of a topological charge and a helicity of the optical vortex beam on needle geometry, such as needle height and screw orientation, is quantitatively demonstrated. This dependence agrees with experimental measurements partially. Furthermore, we found that the presence of structure formation can be evaluated by extracting only the radial component of the force field and solving the one-dimensional equation of motion in the radial direction.

Experimental and numerical studies on the use of a needle for variable capacity single-phase ejectors

Vapor ejectors raise interest for cooling applications given their low electrical consumption, however, a single ejector suffers from a lack of capacity flexibility. The current study explores the use of an adjustable needle to control the primary nozzle throat area (At) in view to allow variable ejector capacity. Tests were done using a large scale test bench working with the refrigerant R245fa. CFD simulations using k-ω SST and, for the first time, Scale-Adaptive Simulation (SAS), were also done. A comparison of the simulation results using the two different turbulence models (ω SST and SAS) showed negligible difference. Also, the simulation results with the ω SST model showed good agreement with the experimental values. For fixed operating conditions, the simulation showed that the reduction of the throat area from 1.00At to 0.61At increased the entrainment ratio from 24% to 56%, but reduced the critical outlet pressure from 440 kPa to 315 kPa. For all conditions, the transiting exergy efficiency ηtr,ex first increased with the increase of the outlet pressure (Pout), reached a maximum value when Pout is close to the critical outlet pressure (Pcrit), and then decreased sharply due to the decrease of the entrainment ratio. Finally, CFD modelings with a blunt tip needle to see the effect of the needle geometry and in order to have a lower throat area value of 0.39At. This novel study shows that the ejector equipped with a needle is able to maintain ejector performance with changes in operating conditions.

Failure of Soft Biological Tissues Inserting of Needles

This research aims the failure of soft biological tissues in the context of minimally invasive surgery based on numerical analysis that fits experimental results. Using robotic arms for assistance in medical procedures during the last years led to new trends in the development of devices for inserting needles into biological tissues, as well as expansion of studies for the development of new types of needles. A better understanding of the mechanical interaction between a medical tool and a biological tissue requires not only detailed investigation and experimental testing but also study for evaluation of the tissue characteristics and the effect of the needle geometry on the process. The purpose of this first study is to investigate the mechanical properties of soft medical tissues, and the force reaction at needles and to study necessary aspects for performing FEA numerical analysis with better results and better correlation with experimental data.

Development of a novel MR‐conditional microwave needle for MR‐guided interventional microwave ablation at 1.5T

To develop an MR-conditional microwave needle that generates a spherical ablation zone and clear MRI visibility for MR-guided microwave ablation. An MR-conditional microwave needle consisting of zirconia tip and TA18 titanium alloy tube was investigated. The numerical model was created to optimize the needle's geometry and analyze its performance. A geometrically optimized needle was produced using non-magnetic materials based on the electromagnetics simulation results. The needle's mechanical properties were tested per the Chinese pharmaceutical industry standard YY0899-2013. The MRI visibility performance and ablation characteristics of the needle was tested both in vitro (phantom) and in vivo (rabbit) at 1.5T. The RF-induced heating was evaluated in ex vivo porcine liver. The needle's mechanical properties met the specified requirements. The needle susceptibility artifact was clearly visible both in vitro and in vivo. The needle artifact diameter (A) was small in in vivo (Ashaft: 4.96 ± 0.18 mm for T1W-FLASH, 3.13 ± 0.05 mm for T2-weighted fast spin-echo (T2W-FSE); Atip: 2.31 ± 0.09 mm for T1W-FLASH, 2.29 ± 0.08 mm for T2W-FSE; tip location error [TLE]: -0.94 ± 0.07 mm for T1W-FLASH, -1.10 ± 0.09 mm for T2W-FSE). Ablation zones generated by the needle were nearly spherical with an elliptical aspect ratio ranging from 0.79 to 0.90 at 30 W, 50 W for 3, 5, 10min duration ex vivo ablations and 0.86 at 30 W for 10min duration in vivo ablations. The designed MR-conditional microwave needle offers excellent mechanical properties, reliable MRI visibility, insignificant RF-induced heating, and a sufficiently spherical ablation zone. Further clinical development of MR-guided microwave ablation appears warranted.

A mechanistic predictive model for ultrasound guided insertion process of Ø 0.11 mm Z-pins

The insertion of finer Z-pins is a key issue for utilization of their reinforcement potential in Z-pinned composite laminates. This paper aims to reveal the insertion mechanisms of the ultrasound guided insertion process of Ø 0.11 mm Z-pins. Taking into account the fibre deformation, fibre–matrix interface, needle tip cutting and needle-prepreg contact, a new mechanical model is proposed to predict the change of insertion force during the insertion process. It is found that the application of ultrasonic vibration can minimize frictional effect and reduce fibre fracture, thus significantly decreasing the insertion force. The traditional two-phase insertion mechanism is transformed into single-phase insertion mechanism due to ultrasonic vibration. Based on this model, the effects of process parameters (including vibration amplitude, vibration frequency, feed rate and needle geometry) on the insertion force can be determined. Then Z-pin insertion experiments are performed on the prepreg sample to verify the proposed model. Results show that the model can capture the insertion mechanisms during the ultrasound guided insertion and predictions are in excellent agreement with the experimental measurements.

Evaluating the role of carbon quantum dots covered silica nanofillers on the partial discharge performance of transformer insulation

The article presents the experimental results on the role of carbon quantum dots (CQD) covered silica nanofillers on the partial discharge (PD) properties of transformer oil insulation. The improvement in PD performance of nanofiller blend oil is tested with increased voltage gradient and nanofiller concentration. PD of nanoblend oils for various concentrations of modified silica ranging from 0 to 0.1%wt was measured. PD activity of the test samples is simulated in the laboratory with needle, rod and plane electrode geometry combinations. The facets of PD signals such as PD magnitude, PD inception and time duration of PD extracted from phase-resolved partial discharge patterns were analyzed. Detailed time-frequency domain evaluation of PD pulse is carried out. The enclosure of CQD-SiO2 nanostructures has considerably improved the inception voltage up to 23% than base transformer oil and SiO2 nanofluid. Magnitude of discharge is noticeably reduced by the influence of CQD-treated SiO2 nanoparticles in mineral oil irrespective of the electrode geometry.

In-Plane Si Microneedles: Fabrication, Characterization, Modeling and Applications.

Microneedles are getting more and more attention in research and commercialization since their advancement in the 1990s due to the advantages over traditional hypodermic needles such as minimum invasiveness, low material and fabrication cost, and precise needle geometry control, etc. The design and fabrication of microneedles depend on various factors such as the type of materials used, fabrication planes and techniques, needle structures, etc. In the past years, in-plane and out-of-plane microneedle technologies made by silicon (Si), polymer, metal, and other materials have been developed for numerous biomedical applications including drug delivery, sample collections, medical diagnostics, and bio-sensing. Among these microneedle technologies, in-plane Si microneedles excel by the inherent properties of Si such as mechanical strength, wear resistance, biocompatibility, and structural advantages of in-plane configuration such as a wide range of length, readiness of integration with other supporting components, and complementary metal-oxide-semiconductor (CMOS) compatible fabrication. This article aims to provide a review of in-plane Si microneedles with a focus on fabrication techniques, theoretical and numerical analysis, experimental characterization of structural and fluidic behaviors, major applications, potential challenges, and future prospects.

FEA Modeling of Soft Tissue Interaction for Active Needles With a Rotational Tip Joint

A finite element analysis (FEA) model was developed for investigating the design and the tissue interaction of actively steerable needles with a rotational tip joint in soft tissue, based on the coupled Eulerian-Lagrangian (CEL) mesh. The new model is algorithmically simple in that the proposed CEL strategy allows needle insertion simulations along non-predetermined paths in soft tissue without the re-mesh at every direction change of the needle tip. For the features, various steering motions can be simulated and studied for different needle designs in a simpler approach by changing the needle geometry and boundary conditions. The developed FEA model, using the thoroughly measured material properties, was validated for predicting insertion path and estimating the tissue interaction forces inside two different gelatin tissue phantoms. Further, using the validated model, the effect of tip geometry on tissue was briefly investigated. Given bevel angles, it was found that the ratio of tip length to the diameter dominates the tissue damage gradient. The results demonstrate that the proposed model effectively examines the steering and tissue insertion of actively steerable needles and investigates the tip design to minimize the tissue damage by the needle steering.

Micropatterning of acoustic droplet vaporization in acoustically-responsive scaffolds using extrusion-based bioprinting

Acoustically-responsive scaffolds (ARSs) are composite hydrogels that respond to ultrasound in an on-demand, spatiotemporally-controlled manner due to the presence of a phase-shift emulsion. When exposed to ultrasound, a gas bubble is formed within each emulsion droplet via a mechanism termed acoustic droplet vaporization (ADV). In previous in vitro and in vivo studies, we demonstrated that ADV can control regenerative processes by releasing growth factors and/or modulating micromechanics in ARSs. Precise, spatial patterning of emulsion within an ARS could be beneficial for ADV-induced modulation of biochemical and biophysical cues. However, precise patterning is limited using conventional bulk polymerization techniques. Here, we developed an extrusion-based method for bioprinting ARSs with micropatterned structures. Emulsions were loaded within bioink formulations containing fibrin, hyaluronic acid and/or alginate. Experimental as well as theoretical studies elucidated the interrelations between printing parameters, needle geometry, rheological properties of the bioink, and the process-induced mechanical stresses during bioprinting. The shear thinning properties of the bioinks enabled use of lower extrusion pressures resulting in decreased shear stresses and shorter residence times, thereby facilitating high viability for cell-loaded bioinks. Bioprinting yielded greater alignment of fibrin fibers in ARSs compared to conventionally polymerized ARSs. Bioprinted ARSs also enabled generation of ADV at high spatial resolutions, which were otherwise not achievable in conventional ARSs, and acoustically-driven collapse of ADV-induced bubbles. Overall, bioprinting could aid in optimizing ARSs for therapeutic applications.