Prototyping Techniques Research Articles

Development of new surgical mesh geometries with different mechanical properties using the design freedom of 3D printing

AbstractThe emergence of new rapid prototyping techniques such as melt electrowriting and their application in the development of medical devices, enables new geometries for surgical meshes that were previously limited by current conventional manufacturing methods. The change in geometry allows a direct impact on the mechanical behavior of surgical meshes using identical polymers. The adaptation of the mechanical properties of surgical meshes, based on sinusoidal auxetic design with varying amplitude and number of waves per total fiber length, aims to improve biocompatibility by mimicking and matching the mechanical properties of vaginal soft tissue, which is not provided by current polypropylene nondegradable meshes. The auxetic design of the meshes can supply dimensionally stable pores under tensile load, which is a limitation of the current meshes. The mechanical properties can be controlled with mesh deformations up to 100%, Young's modulus ranging from 50 to 400 N/mm2 and a variable toe region. The printed meshes show an effective porosity of over 70% and are lightweight or ultra‐lightweight. By combining matching mechanical properties with good porosity and weight, 3D printed sinusoidal meshes, made of biodegradable Poly‐ε‐caprolactone, show promising results to improve surgical meshes for use in pelvic organ prolapse repair.

Advanced Composite Materials Utilized in FDM/FFF 3D Printing Manufacturing Processes: The Case of Filled Filaments.

The emergence of additive manufacturing technologies has brought about a significant transformation in several industries. Among these technologies, Fused Deposition Modeling/Fused Filament Fabrication (FDM/FFF) 3D printing has gained prominence as a rapid prototyping and small-scale production technique. The potential of FDM/FFF for applications that require improved mechanical, thermal, and electrical properties has been restricted due to the limited range of materials that are suitable for this process. This study explores the integration of various reinforcements, including carbon fibers, glass fibers, and nanoparticles, into the polymer matrix of FDM/FFF filaments. The utilization of advanced materials for reinforcing the filaments has led to the enhancement in mechanical strength, stiffness, and toughness of the 3D-printed parts in comparison to their pure polymer counterparts. Furthermore, the incorporation of fillers facilitates improved thermal conductivity, electrical conductivity, and flame retardancy, thereby broadening the scope of potential applications for FDM/FFF 3D-printed components. Additionally, the article underscores the difficulties linked with the utilization of filled filaments in FDM/FFF 3D printing, including but not limited to filament extrusion stability, nozzle clogging, and interfacial adhesion between the reinforcement and matrix. Ultimately, a variety of pragmatic implementations are showcased, wherein filled filaments have exhibited noteworthy benefits in comparison to standard FDM/FFF raw materials. The aforementioned applications encompass a wide range of industries, such as aerospace, automotive, medical, electronics, and tooling. The article explores the possibility of future progress and the incorporation of innovative reinforcement materials. It presents a plan for the ongoing growth and application of advanced composite materials in FDM/FFF 3D printing.

Experimental Investigation of SPIF Process for Conical Frustum

In sheet metal industries, single point incremental forming (SPIF) is a popular technology for quick prototyping and small series manufacturing techniques. In producing specific components with complicated geometries, the technique has become known for its flexibility, effectiveness, and simplicity of usage. The objective of this research work is to carry out the numerical investigation of the SPIF process to study the effect of different parameters on the formability for truncated cone. Al 1060 grade of aluminium is used for this study which is commonly used for kitchenware, reflectors, electronic components etc; where strength is not a major concern. Three dimensional models were developed for different set of parameters using commercial finite element software ABAQUS 6.13 with Dynamic/Explicit solver using solid mechanics model. Taguchi analysis has been carried out to find the effect of parameters (Tool rotational speed, Feed, Step size, Tool diameter and Wall angle) on thickness reduction. Each parameter was varied for three levels and L9 orthogonal array was used. The ANOVA tool has been used to summarize the contribution of each variable. Results have been compared with reported experimental results for validation. The process modelling is concluded with a brief overview of approaches for improving part quality.

Tapping the potential of rapid prototyping techniques in creating a paradigm shift in the fabrication of occlusal splints

PurposeThis study aims to cover the overall gamut of rapid prototyping processes and biomaterials used for the fabrication of occlusal splints in a comprehensive manner and elucidate the characteristics of the materials, which are essential in determining their clinical efficacy when exposed to oral surroundings.Design/methodology/approachA collective analysis of published articles covering the use of rapid prototyping technologies in the fabrication of occlusal splints, including manufacturing workflow description and essential properties (mechanical- and thermal-based) evaluation of biocompatible splinting materials, was performed.FindingsWithout advances in rapid prototyping processes and materials engineering, occlusal splints would tend to underperform clinically due to biomechanical limitations.Social implicationsThree-dimensional printing can improve the process capabilities for commercial customization of biomechanically efficient occlusal splints.Originality/valueRapid technological advancement in dentistry with the extensive utilization of rapid prototyping processes, intra-oral scanners and novel biomaterial seems to be the potential breakthrough in the fabrication of customized occlusal splints which have endorsed occlusal splint therapy (OST) as a cornerstone of orthodontic treatment.

Soft Airflow Sensors With Artificial Hair Structures and Printed Ionogel Channels for Wind Gust Detection for Small Uncrewed Vehicles

This article describes the design of a soft airflow sensor capable of detecting the direction and the magnitude of airflow, taking advantage of an additive manufacturing technique for rapid prototyping. The sensor consists of an artificial hair structure and conductive ionogel channels. The artificial hair, made by 3-D printing, is designed to maximize the moments at the base caused by the airflows applied to the hair structure. The ionogel channels are directly printed on a flexible printed circuit board and then embedded in an elastomeric layer. A compact readout circuit is prepared to acquire the impedance information from the sensing channels. The sensor shows reliable and repeatable responses to unidirectional airflows ranging from 6 to 13 m/s. A clear relationship between the applied loads and the sensor outputs is observed. We also demonstrate the performance and the application of the proposed airflow sensor by installing it on a small uncrewed ground vehicle that achieves stable operation through the detection of atmospheric disturbances.

Predictive modeling of mechanical properties for fused deposition modeling parts: A focus on processing and environmental parameters

Fused Deposition Modelling (FDM) is a widely used additive manufacturing technique for prototyping and manufacturing functional parts due to its cost-effectiveness and low waste generation. The mechanical properties of FDM parts depend on multiple processing parameters and environmental conditions. Due to the complex physical phenomena of FDM, it is a challenge to accurately determine part properties. These properties are generally determined after performing experimental investigation which is time consuming and expensive. Alternatively, predictive models developed for determining part properties have proved to be a valuable tool. However, these models are typically developed using data from a single printer and do not consider environmental parameters as an input factor. To address these shortcomings, a data-driven multi-step scalable modeling technique that provide the ability to gather data from multiple sources is presented. This technique is used to develop models for predicting mechanical properties using experimental data from multiple sources resulting in models that are robust compared to models developed using data from one printer. Additionally, one environmental parameter has been introduced as the input factor. Regression and Artificial Neural Network models are developed to predict mechanical properties using experimental data from two printers. Five processing and environmental parameters namely, extrusion temperature, layer thickness, print bed temperature, print speed and humidity are used as the input factors. These models predict the toughness and tensile strength of the parts. The experimental values from the two printers are compared to the predicted values to demonstrate the superior predictive capabilities of the models. Finally, to demonstrate the scalability and utility of the proposed technique, data from one more printer is introduced and is used to develop regression models.

RCM adjustment for a double-parallelogram based RCM mechanism used for MIS robots

The inevitable errors in the manufacturing, assembly, and testing of a remote center-of-motion (RCM) mechanism lead to the erroneous link parameters which deviate its geometry. Consequently, the motion, as well as the force, become non-zero at the entry port to the patient’s body which is undesirable. To address this issue, the current work first presents the accurate kinematic model of the RCM of an exemplary double-parallelogram-based RCM mechanism. Thereafter, it introduces the RCM adjustment concept and a flexure-based compliant mechanism to nullify/minimize the said deviation. For the analytical design of the flexure element, this paper makes the required design calculations and performs the finite element analysis. It is followed by the disclosure of the RCM Adjustment System and a systematized method of RCM adjustment for a mechanically constrained RCM device. The devised system is based on the prescribed compliant mechanism design and is advantageous, over the traditional RCM adjustments. The potential of the proposed concept lies in the fact that it is not limited to the adopted mechanism only rather, it is extendable to other mechanisms as well which was missing in the prior art. In addition, it offers a more simplified and economical design. Further, an initial prototype of the exemplary mechanism is manufactured using laser micromachining and rapid prototyping techniques. Both analytical as well as physical validations have been performed which proved the efficacy of the proposed kinematic modeling concept. Furthermore, the prototype of the introduced RCM Adjustment System is manufactured as a single-piece design which demonstrated its effectiveness. The preferred embodiment of the same is the said double-parallelogram-based RCM mechanism which is most widely used for robot-assisted minimally invasive surgery (RAMIS). It is designed in a SolidWorks environment and manufactured using Al6101-T6 and SS304 as link material, and a variety of standard elements.

Saturation of the MEA solution with CO2: Absorption prototype and experimental technique

The carbon dioxide (CO2) emissions from thermoelectric power plants contribute to global warming. The Monoethanolamine (MEA) solution is the most widely used solvent for CO2 removal processes from these power plants with the disadvantage that it is expensive and corrosive at high concentrations. In this work, an experimental methodology is developed to fix the operating flow ratio (L/G) that ensures the maximum absorption capacity of MEA solution. The absorption system prototype and the experimental saturation technique are detailed. The main parameters of the experimental technique were the amount (0.65 and 1.30 kg) and concentrations (10,15, 20, 25, and 30 wt%) of MEA solution with CO2 inlet gas concentration (12.5 vol%). The experimental technique shows that MEA saturation occurs when the maximum temperature increase in the solution. Continuous tests were developed to operate the absorption system with the maximum absorption capacity of the MEA solution. The results show that the temperature increases in the MEA solution are a function of the flow rates (L/G) and the MEA concentration. Furthermore, the density, viscosity, and refractive index of CO2-free and CO2-saturated MEA solution at concentrations of MEA below 30 wt% are also measured in this work.

A novel integrated platform enabling simultaneous microextraction and chemical analysis on-chip

The nature and size of biological, pharmaceutical or environmental analytes complicates their extraction and detection outside of laboratories and near the site of interest by the current chromatographic methods because they require the combination of bulky extraction and detection methods. In order to solve this inefficient centralized control, a ground-breaking and miniaturized proof of concept platform is developed in this work. The platform integrates for the very first time an electro-membrane extraction process and an accurate analyte quantification method in the same device, by using electrochemical impedance spectroscopy (EIS) as analytical technique. The microfluidic flow cell, including the microfluidic components, is fabricated in polymeric materials by rapid prototyping techniques. It comprises a four-electrode platinum thin-film chip that enables the control of the microextraction and the full characterization of the process, i.e., extraction efficiency determination, at the same time. The microfluidic system has been simulated by using computational tools, enabling an accurate prediction of the effect of the different experimental conditions in the microextraction efficiency. The platform has been validated in the microextraction of the nonsteroidal anti-inflammatory drug ketoprofen in a range from 0.5 ppm to 6 ppm. The predicted microextraction efficiency values obtained by EIS were compared with those calculated from the high-performance liquid chromatography coupled with a diode array detector (HPLC-DAD), showing an excellent agreement. This validates the high potential of this integrated and miniaturized platform for the simultaneous extraction by electro-membrane and also the analysis within the platform, solving one of the of most important limitations of current systems.

Detecting and characterizing special nuclear material for nuclear nonproliferation applications

There is an urgent need for new, better instrumentation and techniques for detecting and characterizing special nuclear material (SNM), i.e., highly enriched uranium and plutonium. The development of improved instruments and techniques requires experiments performed with the SNM itself, which is of limited availability. This paper describes the findings of experiments performed at the National Criticality Experiments Research Center conducted using new instruments and techniques on unclassified, kg-quantity SNM objects. These experiments, performed in the framework of the Department of Energy, National Nuclear Security Administration Consortium for Monitoring, Technology, and Verification, focused on detecting, characterizing, and localizing SNM samples with masses ranging from 3.3 to 13.8 kg, including plutonium and highly enriched uranium using prototype detectors and techniques. The work demonstrates SNM detection and characterization using recently-developed prototype detection systems. Specifically, we present new results in passive detection and imaging of plutonium and uranium objects using gamma-ray and dual particle (fast neutron and gamma-ray) imaging. We also present a new analysis of the delayed neutron emissions during active interrogation of uranium using a neutron generator.

A semi-empirical approach to calibrate simulation models for semiconductor devices

Semiconductor device optimization using computer-based prototyping techniques like simulation or machine learning digital twins can be time and resource efficient compared to the conventional strategy of iterating over device design variations by fabricating the actual device. Ideally, simulation models require perfect calibration of material parameters for the model to represent a particular semiconductor device. This calibration process itself can require characterization information of the device and its precursors and extensive expert knowledge of non characterizable parameters and their tuning. We propose a hybrid method to calibrate multiple simulation models for a device using minimal characterization data and machine learning-based prediction models. A photovoltaic device is chosen as the example for this technique where optical and electrical simulation models of an industrially manufactured silicon solar cell are calibrated and the simulated device performance is compared with the measurement data from the physical device.

APPLICATION IN CULTURAL HERITAGE OF STEREOLITOGRAPHY TECHNIQUES FOR THE 3D REPRODUCTION

Abstract. With the use of stereolithography, one of the most widespread and old rapid prototyping techniques, it is possible to reproduce objects, damaged or missing parts, faithful replicas of interest in the field of Cultural Heritage. In this work, some of the applications of the stereolithography technique to replicate objects or missing parts of artistic or cultural interest, are illustrated. The aim of the Authors is to highlight the potential, the advantages, and also the limits if any, of this technique when applied in the field of Cultural Heritage for various needs, reporting some real cases of objects obtained in the laboratory with stereolithography.

Thermal and Oxidative Aging Effects of Polyamide-11 Powder Used in Multi-Jet Fusion.

The transition of additive manufacturing (AM) from a technique for rapid prototyping to one for manufacturing of near net or net components has been led by the development of methods that can repeatedly fabricate quality parts. High-speed laser sintering and the recently developed multi-jet fusion (MJF) processes have seen quick adoption from industry due to their ability to produce high-quality components relatively quickly. However, the recommended refresh ratios of new powder led to notable amounts of used powder being discarded. In this research, polyamide-11 powder, typically used in AM, was thermally aged to investigate its properties at extreme levels of reuse. The powder was exposed to 180 °C in air for up to 168 h and its chemical, morphological, thermal, rheological, and mechanical properties were examined. To decouple the thermo-oxidative aging phenomena from AM process related effects, such as porosity, rheological and mechanical properties characterisation was performed on compression-moulded specimens. It was found that exposure notably affected the properties of both the powder and the derived compression-moulded specimens within the first 24 h of exposure; however, consecutive exposure did not have a significant effect.

Rapid Prototyping Techniques for the Development of a Take-Home Surgical Anastomosis Simulation Model

The objective of this paper is to describe the techniques and process of developing and testing a take-home surgical anastomosis simulation model. Through an iterative process, a simulation model was customized and designed to target specific skill development and performance objectives that focused on anastomotic techniques in thoracic surgery and consist of 3D printed and silicone molded components. Various manufacturing techniques such as silicone dip spin coating and injection molding have been described in this paper and explored as part of the research and development process. The final prototype is a low-cost, take-home model with reusable and replaceable components. The study took place at a single-center quaternary care university-affiliated hospital. The participants included in the model testing were 10 senior thoracic surgery trainees who completed an in-person training session held during an annual hands- on thoracic surgery simulation course. Feedback was then collected in the form of an evaluation of the model from participants. All 10 participants had an opportunity to test the model and complete at least 1 pulmonary artery and bronchial anastomosis. The overall experience was rated highly, with minor feedback provided regarding the set- up and fidelity of the materials used for the anastomoses. Overall, the trainees agreed that the model was suitable for teaching advanced anastomotic techniques and expressed an interest in being able to use this model to practice skill development. Developed simulation model can be easily reduced, with customized components that accurately simulate real-life vascular and bronchial components suitable for training of anastomoses technique amongst senior thoracic surgery trainees.

Terahertz Beam Steering with Curved Metasurfaces

Considerable recent research interest has focused on the possibility of using metasurfaces for manipulation of terahertz wavefronts. For example, metasurfaces allow a beam to be targeted in any desired direction using strategically placed meta-elements. With rapid prototyping techniques, metasurfaces can be fabricated quickly and at a low cost. These techniques also permit the fabrication of metasurfaces on flexible substrates which can be bent easily. This opens the possibility of employing such devices as conformable arrays on non-flat surfaces. To explore this idea, we experimentally and numerically analyze the performance of a terahertz metasurface printed on paper, as a function of its radius of curvature. We observe that when the metasurface is bent, the direction of the refracted beam is minimally impacted and the performance of the metasurface remains very similar to when it is flat. This conclusion will simplify the design and modeling criteria for conformable metasurfaces.

A high sensitivity and multi-axis fringing electric field based capacitive tactile force sensor for robot assisted surgery

This paper presents a design of multi-axis tactile force sensor using the fringe effect of an electric field between stationary patterned electrodes. The unique configuration of the electrodes consisting of four separate square-shaped sensing electrodes, with each encircled by excitation electrodes, allows to achieve enhanced fringe field effect and hence sensitivity. The proposed sensor can decouple the normal, shear and angular shear applied forces. The sensor is fabricated using low-cost rapid prototyping techniques with flexible Ecoflex 00–30 and silicone rubber RTV-528 as the elastomers for contact with the environment. An analytical model is developed that correlates the nominal capacitance of the sensor with that of the geometric dimensions of the stationary electrodes and air cavity height between the electrodes and elastomer. The force measurement ranges in the normal, shear, and angular axis are 5 N, 1.5 N, and 1 N respectively. The sensor shows a perfectly linear response, repeatability, and a low hysteresis error, thermal stability and robustness to the environmental interferences that makes it suitable to be used for force feedback in minimally invasive robotic surgery.

Graphene-Based Smart Insole Sensor for Pedobarometry and Gait Analysis

Pedobarography and gait analysis are crucial components of healthcare, given their close association with chronic illnesses. Wearable electronics, such as smart insole systems, have emerged as a promising technology for remote and long-term gait monitoring, providing more accurate data in real time. To meet the demands of wearable electronics, components with both flexibility and sensitivity are crucial. This study employed low-cost and rapid prototyping techniques to develop a flexible piezoresistive pressure sensor with a graphene nanoplatelet/ polycaprolactone composite spray-deposited on a fiber-based commercial insole. The sensor demonstrated a pressure range of up to 400 kPa and high linear sensitivity (∼ 0.376 kPa-1), making it suitable for pedobarography. Additionally, to test its practical application, the sensor was linked to a low-power programmable data logging and transmitting device for data acquisition over custom designed android application. The sensor can differentiate various motion states, such as walking, jumping, and running, while also demonstrating potential for long-term stability.

Shoetok Online Shoe Store Application Design to Increase Shoe Sales

The design of the ShoeStok application was carried out using the Design thinking research method to increase shoe sales. This application is designed with an intuitive user interface and provides various payment options, stock checking features, product availability notifications, as well as reviews and ratings of products that have been purchased. Design thinking is used to find the best solution for the problem at hand, with the stages of understanding, ideation, prototyping, and testing. Wireframing, prototyping, and user testing techniques are used to determine the layout and elements that will be displayed in the application. The result of designing this application is a Shoestok e-commerce application which has an intuitive UI and is easy for customers to use, which is expected to help increase shoe sales.

Lignin-enriched tricalcium phosphate/sodium alginate 3D scaffolds for application in bone tissue regeneration

The bone is a connective, vascularized, and mineralized tissue that confers protection to organs, and participates in the support and locomotion of the human body, maintenance of homeostasis, as well as in hematopoiesis. However, throughout the lifetime, bone defects may arise due to traumas (mechanical fractures), diseases, and/or aging, which when too extensive compromise the ability of the bone to self-regenerate. To surpass such clinical situation, different therapeutic approaches have been pursued. Rapid prototyping techniques using composite materials (consisting of ceramics and polymers) have been used to produce customized 3D structures with osteoinductive and osteoconductive properties. In order to reinforce the mechanical and osteogenic properties of these 3D structures, herein, a new 3D scaffold was produced through the layer-by-layer deposition of a tricalcium phosphate (TCP), sodium alginate (SA), and lignin (LG) mixture using the Fab@Home 3D-Plotter. Three different TCP/LG/SA formulations, LG/SA ratio 1:3, 1:2, or 1:1, were produced and subsequently evaluated to determine their suitability for bone regeneration. The physicochemical assays demonstrated that the LG inclusion improved the mechanical resistance of the scaffolds, particularly in the 1:2 ratio, since a 15 % increase in the mechanical strength was observed. Moreover, all TCP/LG/SA formulations showed an enhanced wettability and maintained their capacity to promote the osteoblasts' adhesion and proliferation as well as their bioactivity (formation of hydroxyapatite crystals). Such results support the LG inclusion and application in the development of 3D scaffolds aimed for bone regeneration.

Customizable Fabrication Process for Flexible Carbon-Based Electrochemical Biosensors

In recent research, 3D printing has become a powerful technique and has been applied in the last few years to carbon-based materials. A new generation of 3D-printed electrodes, more affordable and easier to obtain due to rapid prototyping techniques, has emerged. We propose a customizable fabrication process for flexible (and rigid) carbon-based biosensors, from biosensor design to printable conductive inks. The electrochemical biosensors were obtained on a 50 µm Kapton® (polyimide) substrate and transferred to a 500 µm PDMS substrate, using a 3D-extrusion-based printing method. The main features of our fabrication process consist of short-time customization implementation, fast small-to-medium batch production, ease of electrochemical spectroscopy measurements, and very good resolution for an extrusion-based printing method (100 µm). The sensors were designed for future integration into a smart wound dressing for wound monitoring and other biomedical applications. We increased their sensibility with electro-deposited gold nanoparticles. To assess the biosensors’ functionality, we performed surface functionalization with specific anti-N-protein antibodies for SARS-CoV 2 virus, with promising preliminary results.