Insertion Force Research Articles

Damage Analysis of CFRP Hybrid Bonded-Bolted Joint during Insertion of Interference-Fit Bolt.

In this study, experiments and finite element analysis (FEA) were used to evaluate the impact of interference-fit sizes on CFRP hybrid bonded-bolted (HBB) joint damage during bolt insertion. The specimens were designed in accordance with the ASTM D5961 standard and bolt insertion tests were performed at selected interference-fit sizes (0.4%, 0.6%, 0.8%, and 1%). Damage to composite laminates was predicted using the Shokrieh-Hashin criterion and Tan's degradation rule via the user subroutine USDFLD, while damage to the adhesive layer was simulated by the Cohesive Zone Model (CZM). The corresponding bolt insertion tests were performed. The variation of insertion force with interference-fit size was discussed. The results showed that matrix compressive failure was the main failure mode. With the growth of the interference-fit size, more failure modes appeared, and the failure region expanded. Regarding the adhesive layer, it did not completely fail at the four interference-fit sizes. This paper will be helpful in designing composite joint structures and especially for understanding CFRP HBB joint damage and failure mechanisms.

A Tool to Enable Intraoperative Insertion Force Measurements for Cochlear Implant Surgery.

Residual hearing preservation during cochlear implant (CI) surgery is closely linked to the magnitude of intracochlear forces acting during the insertion process. So far, these forces have only been measured in vitro. Therefore, the range of insertion forces and the magnitude of damage-inducing thresholds in the human cochlea in vivo remain unknown. We aimed to develop a method to intraoperatively measure insertion forces without negatively affecting the established surgical workflow. Initial experiments showed that this requires the compensation of orientation-dependent gravitational forces. We devised design requirements for a force-sensing manual insertion tool. Experienced CI surgeons evaluated the proposed design for surgical safety and handling quality. Measured forces from automated and manual insertions into an artificial cochlea model were evaluated against data from a static external force sensor representing the gold standard. The finalized manual insertion tool uses an embedded force sensor and inertial measurement unit to measure insertion forces. The evaluation of the proposed design shows the feasibility of orientation-independent insertion force measurements. Recorded forces correspond well to externally recorded reference forces after reliable removal of gravitational disturbances. CI surgeons successfully used the tool to insert electrode arrays into human cadaver cochleae. The presented positive evaluation poses the first step towards intraoperative use of the proposed tool. Further in vitro experiments with human specimens will ensure reliable in vivo measurements. Intraoperative insertion force measurements enabled by this tool will provide insights on the relationship between forces and hearing outcomes in cochlear implant surgery.

Autonomous Respiratory Motion Compensated Robot for CT-Guided Abdominal Radiofrequency Ablations

Radiofrequency ablation (RFA) is an effective minimally-invasive treatment used for a variety of solid tumor cancers, including lung, breast, kidney, pancreatic, and liver. However, effective RFA for abdominal tumors relies on accurate ablation needle targeting, which can be a challenging task due to respiratory motion. This paper presents the design, fabrication, modeling, and benchtop characterization of a CT-guided parallel robot, and a novel respiration motion compensation protocol (RMCP) for effective robot-assisted abdominal RFA needle placement. The robot consists of a Stewart platform with a friction drive roller insertion module for autonomous needle deployment. Strain energy models are used to predict needle insertion force, the primary technical contribution of this work, providing a mean error of 0.49±0.28 N. The free-space accuracy characterization experiments indicate that the robotic platform is able to provide a needle tip position and orientation accuracy of 2.00±0.75 mm and 0.81±0.48±, respectively. A dynamic targeting experiment using an ex-vivo liver indicates an improvement in position and orientation error of 57% and 30%, respectively, when using the proposed RMCP. Finally, an animal study using a sexually-mature swine undergoing assisted respiration at nine breaths per minute indicates a 77% reduction in additional insertion displacement when using the RMCP.

Efficacy of an assistive guide tube for improved endoscopic access to gastrointestinal lesions: an in vivo study in a porcine model.

Guide tube-assisted endoscopy for procedures that require repeated endoscopic access is safer and more effective than conventional endoscopy. However, its effectiveness has not been confirmed in animal studies. We assessed the usefulness of guide tube-assisted endoscopic procedures in an in vivo porcine model. Five different guide tube-assisted endoscopic procedures were performed by experienced endoscopists on a pig weighing 32 kg. To evaluate the efficacy of these procedures, we compared the endoscopic approach time when a guide tube was used to that when it was not. Additional endoscopic procedures using a guide tube were performed, including multiple foreign body extractions, multiple polypectomies, and multiple submucosal dissections. To evaluate safety, we compared the insertion force into the proximal esophagus between the guide tube and conventional overtube methods. Using the endoscopic approach with a guide tube required a shorter average approach time to reach the three target lesions than when using the endoscopic approach without a guide tube (p<0.001). Compared to the conventional overtube method, the guide tube method produced a lower average resistance during insertion into the upper esophagus (p<0.001). Guide tube-assisted endoscopic procedures are effective and safe for repeated endoscopic access in an in vivo porcine model.

INFLUENCE OF DILATION ON THE STABILITY OF OSTEOCHONDRAL AUTOGRAFTS IMPLANTED IN CADAVERIC HUMAN FEMURS

The clinical success of osteochondral autografts is heavily reliant on their mechanical stability, as grafts which protrude above or subside below the native cartilage can have a negative effect on the tribological properties of the joint [1]. Furthermore, high insertion forces have previously been shown to reduce chondrocyte viability [2]. Commercial grafting kits may include a dilation tool to increase the diameter of the recipient site prior to insertion. The aim of this study was to evaluate the influence of dilation on the primary stability of autografts.Six human cadaveric femurs were studied. For each femur, four 8.5 × 8mm autografts were harvested from the trochlear groove and implanted into the femoral condyles using a Smith &amp; Nephew Osteochondral grafting kit. Two grafts were implanted into dilated recipient sites (n=12) and two were implanted with no dilation (n=12). Insertion force was measured by partially inserting the graft and applying a load at a rate of 1 mm/min, until the graft was flush with the surrounding cartilage. Push-in force was measured by applying the same load, until the graft had subsided 4mm below congruency. Significance was taken as (p&lt;0.05).Average maximum insertion force of dilated grafts was significantly lower (p&lt;0.001) than their non-dilated equivalent [28.2N &amp; 176.7N respectively]. There was no significant difference between average maximum push-in force between the dilated and non-dilated groups [1062.8N &amp; 1204.2N respectively].This study demonstrated that significantly less force is required to insert dilated autografts, potentially minimising loss of chondrocyte viability. However, once inserted, the force required to displace the grafts below congruency remained similar, indicating a similar degree of graft stability between both groups.

MP35-03 SAFE PASSAGE OF 16 FR URETERAL ACCESS SHEATHS

You have accessJournal of UrologyCME1 Apr 2023MP35-03 SAFE PASSAGE OF 16 FR URETERAL ACCESS SHEATHS Sohrab N. Ali, Amanda McCormac, Minh-Chau Vu, Andrew S. Afyouni, Mitchell O'Leary, Kathryn Osann, Michael Klopfer, Zachary E. Tano, Pengbo Jiang, Roshan M. Patel, Jaime Landman, and Ralph V. Clayman Sohrab N. AliSohrab N. Ali More articles by this author , Amanda McCormacAmanda McCormac More articles by this author , Minh-Chau VuMinh-Chau Vu More articles by this author , Andrew S. AfyouniAndrew S. Afyouni More articles by this author , Mitchell O'LearyMitchell O'Leary More articles by this author , Kathryn OsannKathryn Osann More articles by this author , Michael KlopferMichael Klopfer More articles by this author , Zachary E. TanoZachary E. Tano More articles by this author , Pengbo JiangPengbo Jiang More articles by this author , Roshan M. PatelRoshan M. Patel More articles by this author , Jaime LandmanJaime Landman More articles by this author , and Ralph V. ClaymanRalph V. Clayman More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003269.03AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: During ureteroscopic stone therapy, the insertion of a 14 Fr ureteral access sheath (UAS) results in significant ureteral trauma in upwards of 20% of patients. In attempts to avert such injury, we developed a proprietary UAS force sensor. Our studies indicated that maintaining the force of insertion below 6 N would allow for non-injurious insertion of even a 16 Fr UAS. Herein, we sought to identify the clinical factors associated with the safe deployment of a 16 Fr UAS. METHODS: Two hundred and thirty-eight patients (250 renal units) were subject to having UAS insertion forces recorded. In each case, an attempt was made to initially pass a 16 Fr UAS; if 6 N was reached, the surgeon was advised to downsize to a 14 Fr UAS and if 6 N was again reached, the surgeon was advised to downsize to a 12 Fr UAS. A post-ureteroscopic lesion scale (PULS) was recorded for each case to assess for ureteral injury. Regression models were created to estimate the impact of adjusted variables on PULS value, 16 Fr UAS deployment, and maximum UAS insertion force. RESULTS: A 16 Fr UAS was deployed in 145 (58%) renal units with a mean maximum force of 5.5 N. Two renal units with high-grade ureteral injuries (PULS=3) were noted; however, in both cases, the safety threshold (6 N) was exceeded: 8.36 N and 8.91 N. Preoperative stents were strongly associated with successful passage of a 16 Fr UAS independent of tamsulosin (OR 3.184, p=0.002). Recently treated bacteriuria (OR 1.988, p=0.033), and preoperative antibiotics (OR 1.96, p=0.014) were also independent predictors of successful 16 Fr UAS deployment. Preoperative administration of tamsulosin was not found to be beneficial. CONCLUSIONS: Maintaining an insertion force of ≤ 6 N can avoid significant UAS associated ureteral injuries. Preexisting indwelling stents, recently treated bacteriuria, and preoperative antibiotics favored safe insertion of a 16 Fr UAS. Source of Funding: None © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e469 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Sohrab N. Ali More articles by this author Amanda McCormac More articles by this author Minh-Chau Vu More articles by this author Andrew S. Afyouni More articles by this author Mitchell O'Leary More articles by this author Kathryn Osann More articles by this author Michael Klopfer More articles by this author Zachary E. Tano More articles by this author Pengbo Jiang More articles by this author Roshan M. Patel More articles by this author Jaime Landman More articles by this author Ralph V. Clayman More articles by this author Expand All Advertisement PDF downloadLoading ...

Evaluation of a Bioabsorbable Scaffold and Interlocked Nail System for Segmental Bone Defect

In the current study, we designed and manufactured a scaffold and fixation system for the reconstruction of long-bone segmental defects in a rabbit tibia model. We used biocompatible and biodegradable materials, polycaprolactone (PCL) and PCL soaked with sodium alginate (PCL-Alg) to manufacture the scaffold, interlocking nail and screws using a phase separation casing method. Degradation and mechanical tests on the PCL and PCL-Alg scaffolds indicated that both were suitable for faster degradation and early weight-bearing capacity. PCL scaffold surface porosity facilitated the infiltration of alginate hydrogel through the scaffold. Cell viability results showed that the number of cells increased on Day 7 and decreased marginally by Day 14. For accurate placement of the scaffold and fixation system, a surgical jig was designed and 3D-printed using biocompatible resin in a stereolithography (SLA) 3D printer, then cured with UV light for increased strength. Our cadaver tests using New Zealand White rabbit confirmed our novel jigs' potential for accurate placement of the bone scaffold, intramedullary nail and the alignment of the fixation screws in future reconstructive surgeries on rabbit long-bone segmental defects. Additionally, the cadaver tests confirmed that our designed nails and screws were strong enough to carry the surgical insertion force. Therefore, our designed prototype has the potential for further clinical translational study using the rabbit tibia model.

A parametric study of insertion and retention forces in cantilever hook

Adhesive bonding, mechanical fastening, and snap-fit are all ways for attaching plastic components together. Snap-fit is employed to assemble plastic parts because it is an efficient, cost-effective, and fast joining technique. When it comes to snap-fits, you have two options: separable and inseparable. The term separable refers to the ability of the components to be dismantled successfully without breaking, whereas inseparable refers to the plastic parts being permanently attached. This investigation focuses on cantilever snap-fit since it is frequently used in the automotive, aerospace, and other sectors. Numerous aspects and parameters affect the functioning of snap-fits, notably on the forces of the insertion and retention. The parameters are the feature thickness (Tb), beam length (Lb), beam width (Wb), base radius (Rb), mounting (α) and dismounting angle (β). The forces required to attach and detach the snap-fits are thought to increase as the insertion and retention angles increase. The results can be seen that higher insertion and retention angle contributes to higher insertion and retention forces as portrayed from Set 7 with the value of 1.1052 N and -1.0214 N.

A Sleeve-Based, Micromotion Avoiding, Retractable and Tear-Opening (SMART) Insertion Tool for Cochlear Implantation.

In conventional cochlear implantation, the insertion of the electrode array is strongly affected by the local anatomy and human kinematics. Herein, we present a concept for an insertion tool that allows to optimize the insertion trajectory beyond anatomical constraints and stabilizes the electrode array in manual implantation. A novel sleeve-based design allows the instrument to be compliant and potentially protective to intracochlear structures, while a tear-open mechanism allows it to be removed after insertion by simply retracting the tool. Conventional and tool-guided manual insertions were performed by expert cochlear implant surgeons in an analog temporal bone model that allows to simultaneously record intracochlear pressure, insertion forces and electrode array deformation. Comparison between conventional and tool-guided insertions demonstrate a substantial reduction of maximum insertion forces, force variations, transverse intracochlear electrode array movement, and pressure transients. The presented tool can be utilized in manual cochlear implantation and significantly improves key metrics associated with intracochlear trauma. The instrument may ultimately help improve hearing outcomes in cochlear implantation. The versatile design may be used in both manual cochlear implantation and motorized and robotic insertion, as well as image-guided surgery.

Design of three-section microneedle towards low insertion force and high drug delivery amount using the finite element method

A microneedle has been greatly recognized as one of the most promising devices for novel transdermal drug delivery system due to its capacity of piercing the protective stratum corneum with a minimally invasive and painless manner. During the past two decades, although numerous achievements have been made in the structure and material combination of microneedles, they mostly focus on the pharmacology and functionality of microneedles, and little is reported about how to design the shape of microneedles to reduce insertion force and especially improve penetration efficiency. Using the developed finite element method, we designed three-section microneedles (TSMN) with various sizes and evaluated their maximum insertion force, penetration efficiency, drug delivery amount and strength. The simulation results demonstrate that the well-designed TSMN with shaft width of 60 μm exhibits a lower maximum insertion force of 116.68 mN relative to 167.92 mN of conical microneedle and an effective penetration length of 81.6% relative to 71.38% of conical microneedle. Besides, the optimized TSMN with shaft width of 80 μm shows similar maximum insertion force and 2.3 times the drug delivery amount compared to conical microneedle. These excellent properties are attributed to the optimized design of the shape curve of TSMN sidewall. Such results may provide an inspiration of microneedle design for low insertion force and high penetration efficiency.

Anatomically and mechanically accurate scala tympani model for electrode insertion studies

The risk of insertion trauma in cochlear implantation is determined by the interplay between individual cochlear anatomy and electrode insertion mechanics. Whereas patient anatomy cannot be changed, new surgical techniques, devices for cochlear monitoring, drugs, and electrode array designs are continuously being developed and tested, to optimize the insertion mechanics and prevent trauma. Preclinical testing of these developments is a crucial step in feasibility testing and optimization for clinical application. Human cadaveric specimens allow for the best simulation of an intraoperative setting. However, their availability is limited and it is not possible to conduct repeated, controlled experiments on the same sample. A variety of artificial cochlear models have been developed for electrode insertion studies, but none of them were both anatomically and mechanically representative for surgical insertion into an individual cochlea. In this study, we developed anatomically representative models of the scala tympani for surgical insertion through the round window, based on microCT images of individual human cochleae. The models were produced in transparent material using commonly-available 3D printing technology at a desired scale. The anatomical and mechanical accuracy of the produced models was validated by comparison with human cadaveric cochleae. Mechanical evaluation was performed by recording insertion forces, counting the number of inserted electrodes and grading tactile feedback during manual insertion of a straight electrode by experienced cochlear implant surgeons. Our results demonstrated that the developed models were highly representative for the anatomy of the original cochleae and for the insertion mechanics in human cadaveric cochleae. The individual anatomy of the produced models had a significant impact on the insertion mechanics. The described models have a promising potential to accelerate preclinical development and testing of atraumatic insertion techniques, reducing the need for human cadaveric material. In addition, realistic models of the cochlea can be used for surgical training and preoperative planning of patient-tailored cochlear implantation surgery.

Dynamic Behavior and Insertional Forces of a Precurved Electrode Using the Pull-Back Technique in a Fresh Microdissected Cochlea.

This study evaluated the utility of the pull-back technique in improving perimodiolar positioning of a precurved cochlear implant (CI) electrode array (EA) with simultaneous insertion force profile measurement and direct observation of dynamic EA behavior. Precurved EAs with perimodiolar positioning have improved outcomes compared with straight EAs because of lowered charge requirements for stimulation and decreased spread of excitation. The safety and efficacy of the pull-back technique in further improving perimodiolar positioning and its associated force profile have not been adequately demonstrated. The bone overlying the scala vestibuli was removed in 15 fresh cadaveric temporal bones, leaving the scala tympani unviolated. Robotic insertions of EAs were performed with simultaneous force measurement and video recording. Force profiles were obtained during standard insertion, overinsertion, and pull-back. Postinsertion CT scans were obtained during each of the three conditions, enabling automatic segmentation and calculation of angular insertion depth, mean perimodiolar distance ( Mavg ), and cochlear duct length. Overinsertion did not result in significantly higher peak forces than standard insertion (mean [SD], 0.18 [0.06] and 0.14 [0.08] N; p = 0.18). Six temporal bones (40%) demonstrated visibly improved perimodiolar positioning after the protocol, whereas none worsened. Mavg significantly improved after the pull-back technique compared with standard insertion (mean [SD], 0.34 [0.07] and 0.41 [0.10] mm; p < 0.01). The pull-back technique was not associated with significantly higher insertional forces compared with standard insertion. This technique was associated with significant improvement in perimodiolar positioning, both visually and quantitatively, independent of cochlear size.

A simulation of insertion and retention forces in cantilever hook snap-fit joint

There are numerous methods for joining plastic parts together, including adhesive bonding, mechanical fastening and snap-fit. Snap-fit is used in this study to assemble plastic parts because it is an effective, cost-effective and fast joining technique. When it comes to snap-fits, there are two options: separable and inseparable. Separable indicates that the pieces may be disassembled effectively without breaking, whereas inseparable means that the plastic parts are permanently joined.This study focuses on cantilever snap-fit since it is widely utilized in the automobile, aerospace and other industries. There are numerous parameters that influence the functionality of snap-fits, particularly the forces of insertion and retention. The parameters are the feature thickness (Tb), beam length (Lb), beam width (Wb), base radius (Rb), mounting (α) and dismounting angle (β). The increase of insertion and retention angle is believed to increase the forces required to joint and disjoint the cantilever hook snap-fit.

Trackability of a high-strength thromboresistant hydrogel catheter: An In vitro analysis comparing venous catheter forces in a simulated use pathway

As the need for vascular access devices (VADs) continues to increase, so does the need for innovative designs and materials that can improve placement and optimize patient outcomes. Commercially available peripherally inserted central venous catheters (PICCs) are in high demand due to their ease of use and low cost. However, they are constructed of materials that can contribute to vascular injury and result in complications such as clotting, catheter failure, and infection. This study investigated the surface and frictional properties of a HydroPICC® device constructed of a novel, inherently lubricious bulk hydrogel. Investigators posited that these materials would lower the forces required to advance and retract the HydroPICC® devices and that the measured forces are significantly lower than those of two commercially available PICCs made of conventional thermoplastic polyurethane. The HydroPICC® device had a lower insertion and retraction force compared to both the PowerPICCTM and BioFloTM control devices based on an unpaired, two-sided t-test (P < .001). The HydroPICC® also exhibited a statistically significant decrease in average force when compared to both conventional PICCs (P < .001 and P = .001). When compared to PowerPICCTM, the lubricious high-strength HydroPICC® hydrogel device exhibited an 84% ± 25% reduction in average tracking force; additionally, when compared to a fluoro-oligomer modified TPU catheter (BioFloTM), the HydroPICC® device exhibited a 90 ± 32% reduction in average tracking force. The HydroPICC® technology represents a new method to reduce frictional forces of implantable devices. Clinical trials are needed to determine whether the differences in frictional properties between conventional VADs and HydroPICC® devices translate into improved clinical outcomes.

Modification of gelatin and photocured 3D‐printed resin to prepare biomimetic phantoms for ultrasound‐guided minimally invasive surgeries

AbstractThe main challenge of ultrasound‐guided minimally invasive surgeries is to carry out treatments through small boreholes in the patient's body surface with sub‐millimetric accuracy and facility offered by ultrasound instruments. Thus, the phantoms' biomimetic appearances, acoustic characteristics, and mechanical properties are essential for healthcare professionals. In this study, gelatin and 3D‐printed photo‐resin phantoms were developed for hard and soft tissues, respectively. Using glutaraldehyde (GA) and formaldehyde (FA) to crosslink gelatin phantoms, the mechanical strength, ultrasound velocity, acoustic impedance, needle insertion forces, and antiseptic periods were improved, and the addition of silica nanoparticles raised the acoustic impedance. For 3D‐printed phantoms, the acoustic impedance ascended with hydrophilic polyethylene glycol diacrylate (PEGDA) oligomers. The additives applied in this study successfully made the gelatin and photo‐resin phantoms more mimetic to muscle and bone tissues, allowing their application in preoperative preparations.

Investigation of the effect of different surface treatments for preventing detachment of polyetheretherketone and titanium attachment matrix housings in overdentures: An in vitro study.

The attachment matrix housing (AMH) of implant overdentures is not chemically bonded with acrylic resins. Therefore, AMH may lose due to insertion and removal forces. This study aims to investigate the effects of different surface treatments to reduce the detachment of AMH and to compare the adhesion of the AMH used in implant-supported overdentures made of different materials with the reline acrylic resin. Titanium and polyetheretherketone (PEEK) AMHs were separated into four surface treatment groups; no treatment, airborne-particle abrasion (APA) applied, universal bond (UB) applicated, APA, and UB applicated. Eight millimeters in diameter and ten millimeters tall straws were used to restrain the reline acrylic resin prepared according to the manufacturer's instructions and the resin was injected onto the surface-treated AMH. After the polymerization was completed, the universal testing machine performed the tensile bond strength (TBS) test with a fishing line passed through the acrylic resins. TBS data were analyzed with two and one-way ANOVA and Tukey HSD post hoc tests (α =0.05). According to the two-way ANOVA results, titanium AMHs (103.78 ± 45.98 N) showed higher TBS than PEEK AMHs (67.81 ± 28.61 N). UB applicated titanium groups showed significantly increased TBS values. Using titanium AMHs may be a better choice in situations where clinical aesthetic expectations are unimportant for adhesion to reline acrylic resins. The UB resin significantly increased the bonding of the titanium AMHs with reline resins. The application of UB resin to titanium housings can be easily applied in a clinical situation and can reduce the detachment of the titanium AMHs.

Development of a Force Sensor for a Neuroendovascular Intervention Support Robot System

Neuroendovascular catheterization using fluoroscopy poses the problem to operators and staffs of cumulative radiation exposure. To solve this problem, we are developing a remote-controlled master-slave robot. Because a wire-like elongated treatment device is inserted into a blood vessel using a catheter, the robot requires a sensor to detect the insertion force of the wire. The proposed sensor is integrated into a robot installed in an X-ray fluoroscopy room that is remotely controlled from another room. The features of this sensor include measurement of the insertion force with sufficient accuracy, simple wire attachment, and an inexpensive disposable sensor head, rendering it very suitable for practical application. In this paper, we report on these features, as well as the results of a practical test of the sensor using a cerebrovascular model.

Experimental and simulation investigation of surgical needle insertion into soft tissue mimic biomaterial for minimally invasive surgery (MIS).

The surgical needle insertion process is widely applied in medical interference. During the insertion process, the inhomogeneity and denseness of the soft tissues make it tough to detect the essential tissue damage, a rupture occurs that contains huge forces and material deformations. This study is very important, as all the above-mentioned factors are very significant for modern invasive surgery so that the success rate of the surgery can increase and the patient recovers smoothly. This investigation intends to perform minimally invasive surgical (MIS) procedures and reduce the living tissue damage while performing the biopsy, PCNL, etc. A fracture mechanics method was analyzed to create a needle insertion model which can estimate the needle insertion force during inset in tissue-like PVA gel. The force model was calculated by needle insertion experimentally, and also estimated the needle tip geometry, and diameter influences the fracture toughness. Validate exp. results with simulation results and other papers. It is observed that needle diameter has a significant effect on fracture toughness, whereas the insertion velocity has a slight impact on the fracture toughness. During the rotational needle insertion process, the winds-up of the gel occurs and the diameter of the hole was increasing with increased rpm. Maximum insertion force was noticed in the 27 G needle at 5 mm/s. The interaction function will be less at the maximum fracture development region.

Three-dimensional finite element analysis on cochlear implantation electrode insertion.

Studying the insertion process of cochlear implant (CI) electrode array (EA) is important to ensure successful, sufficient, and safe implantation. A three-dimensional finite element (FE) model was developed to simulate the insertion process. The cochlear structures were reconstructed from an average statistical shape model (SSM) of human cochlea. The electrode is simplified as a long and tapered beam of homogeneous elastic materials, contacting and interacting with the stiff cochlear structures. A quasi-static insertion simulation was conducted, the insertion force and the contact pressure between the electrode and the cochlear wall, were calculated to evaluate the smoothness of insertion and the risk of potential cochlear trauma. Based on this model, different EA designs were analyzed, including the Young's modulus, the straight or bended shape, the normal or a more tapped section size. The influence of the insertion angle was also discussed. Our simulations indicate that reducing the EA Young's modulus, tapering and pre-bending are effective ways to ensure safe and successful EA implantation. This model is beneficial for optimizing EA designs and is potentially useful for designing patient-specific CI surgery.

High density cleanroom-free microneedle arrays for pain-free drug delivery

The purpose of this work is to demonstrate the fabrication process for cleanroom-free solid metal microneedles and perform quantification of insertion profiles. Metal microneedles were created using a modified wirebonding process and inserted into porcine tissue to determine design efficacy. Microneedle arrays were analyzed through optical imaging and scanning electron microscopy. Insertion forces were measured using combined uniaxial load cell and resistance measurement data. Microneedle arrays were successfully inserted into porcine tissue with high repeatability and reliability. These arrays demonstrate lower or equivalent insertion forces (less than 3 N) to other forms of microneedles in the literature without the need for complex cleanroom fabrication processes. The microneedle fabrication method presented here rapidly produces mass manufacturable, high-quality microneedle arrays with minimal insertion forces, able to reliably penetrate tissue samples. The manufacturing method presented here achieved array densities as high as 3200 needles cm−2. These microneedle arrays demonstrate simple fabrication of a reliable, high-density, pain-free drug delivery system, with potential applications in biosensing and electric field modulated drug delivery.