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Ehtezazi T, Kteich A, Abdulkarim R, Anderson V, Algellay M, McCloskey AP, Carter N, Roberts M, Assi S, Al-Jumeily D, Thompson M, Mohamed FA, Sarker SD. Reducing Temperature of Fused Deposition Modelling 3D Printing for Linalool Fast Dissolving Oral Films by Increasing Printer Nozzle Diameter. J Pharm Sci 2024:S0022-3549(24)00136-9. [PMID: 38621439 DOI: 10.1016/j.xphs.2024.04.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2024] [Revised: 04/10/2024] [Accepted: 04/10/2024] [Indexed: 04/17/2024]
Abstract
Oral thrush and throat infections can occur in a wide range of patients. Treatments are available; however, resistance to drugs is a major problem for treating oral and throat infections. Three-dimensional printing (3DP) of fast dissolving oral films (FDFs) of linalool oil may provide an alternative solution. Linalool oil FDFs were printed by fused deposition modelling across 1-18 % w/w linalool content range with nozzle diameters of 0.4 or 1 mm at the temperature range of 150 °C-185 °C. The FDFs were evaluated for physicochemical and mechanical properties. Increasing the printer nozzle diameter to 1 mm allowed reducing the printing temperature from 185 °C to 150 °C; consequently, more linalool was quantified in the films with improved content uniformity. The higher linalool content in the films increased the film disintegration time and mechanical strength. FDFs containing 10% w/w linalool showed clear antifungal activity against Candida albicans. Raman spectroscopy suggested linalool separation from excipients at higher temperature printing. Viscoelastic measurements indicated that to achieve printing; the elastic modulus of molten filament needed to be higher than the loss modulus at low angular frequencies. In conclusion, increasing the printing nozzle diameter may avoid loss of the active ingredient by reducing the temperature of the 3DP process.
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Affiliation(s)
- Touraj Ehtezazi
- Centre for Natural Product Discovery, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, United Kingdom; School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, United Kingdom.
| | - Asmaa Kteich
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, United Kingdom
| | - Rana Abdulkarim
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, United Kingdom
| | - Vicki Anderson
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, United Kingdom
| | - Marwan Algellay
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, United Kingdom
| | - Alice P McCloskey
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, United Kingdom
| | - Neve Carter
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, United Kingdom
| | - Matthew Roberts
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, United Kingdom
| | - Sulaf Assi
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, United Kingdom
| | - Dhiya Al-Jumeily
- School of Computer Science and Mathematics, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, United Kingdom
| | - Molly Thompson
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, United Kingdom
| | - Fazreelia Abu Mohamed
- School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, United Kingdom
| | - Satyajit D Sarker
- Centre for Natural Product Discovery, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, United Kingdom; School of Pharmacy and Biomolecular Sciences, Liverpool John Moores University, Byrom Street, Liverpool, L3 3AF, United Kingdom
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Ece E, Ölmez K, Hacıosmanoğlu N, Atabay M, Inci F. Advancing 3D printed microfluidics with computational methods for sweat analysis. Mikrochim Acta 2024; 191:162. [PMID: 38411762 PMCID: PMC10899357 DOI: 10.1007/s00604-024-06231-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Accepted: 01/18/2024] [Indexed: 02/28/2024]
Abstract
The intricate tapestry of biomarkers, including proteins, lipids, carbohydrates, vesicles, and nucleic acids within sweat, exhibits a profound correlation with the ones in the bloodstream. The facile extraction of samples from sweat glands has recently positioned sweat sampling at the forefront of non-invasive health monitoring and diagnostics. While extant platforms for sweat analysis exist, the imperative for portability, cost-effectiveness, ease of manufacture, and expeditious turnaround underscores the necessity for parameters that transcend conventional considerations. In this regard, 3D printed microfluidic devices emerge as promising systems, offering a harmonious fusion of attributes such as multifunctional integration, flexibility, biocompatibility, a controlled closed environment, and a minimal requisite analyte volume-features that leverage their prominence in the realm of sweat analysis. However, formidable challenges, including high throughput demands, chemical interactions intrinsic to the printing materials, size constraints, and durability concerns, beset the landscape of 3D printed microfluidic devices. Within this paradigm, we expound upon the foundational aspects of 3D printed microfluidic devices and proffer a distinctive perspective by delving into the computational study of printing materials utilizing density functional theory (DFT) and molecular dynamics (MD) methodologies. This multifaceted approach serves manifold purposes: (i) understanding the complexity of microfluidic systems, (ii) facilitating comprehensive analyses, (iii) saving both cost and time, (iv) improving design optimization, and (v) augmenting resolution. In a nutshell, the allure of 3D printing lies in its capacity for affordable and expeditious production, offering seamless integration of diverse components into microfluidic devices-a testament to their inherent utility in the domain of sweat analysis. The synergistic fusion of computational assessment methodologies with materials science not only optimizes analysis and production processes, but also expedites their widespread accessibility, ensuring continuous biomarker monitoring from sweat for end-users.
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Affiliation(s)
- Emre Ece
- UNAM-National Nanotechnology Research Center, Bilkent University, 06800, Ankara, Turkey
- Institute of Materials Science and Nanotechnology, Bilkent University, 06800, Ankara, Turkey
| | - Kadriye Ölmez
- UNAM-National Nanotechnology Research Center, Bilkent University, 06800, Ankara, Turkey
- Institute of Materials Science and Nanotechnology, Bilkent University, 06800, Ankara, Turkey
| | - Nedim Hacıosmanoğlu
- UNAM-National Nanotechnology Research Center, Bilkent University, 06800, Ankara, Turkey
- Institute of Materials Science and Nanotechnology, Bilkent University, 06800, Ankara, Turkey
| | - Maryam Atabay
- UNAM-National Nanotechnology Research Center, Bilkent University, 06800, Ankara, Turkey
- Department of Chemistry, Hacettepe University, 06800, Ankara, Turkey
| | - Fatih Inci
- UNAM-National Nanotechnology Research Center, Bilkent University, 06800, Ankara, Turkey.
- Institute of Materials Science and Nanotechnology, Bilkent University, 06800, Ankara, Turkey.
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Ren Z, Sitti M. Design and build of small-scale magnetic soft-bodied robots with multimodal locomotion. Nat Protoc 2024; 19:441-486. [PMID: 38097687 DOI: 10.1038/s41596-023-00916-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Accepted: 09/21/2023] [Indexed: 02/12/2024]
Abstract
Small-scale magnetic soft-bodied robots can be designed to operate based on different locomotion modes to navigate and function inside unstructured, confined and varying environments. These soft millirobots may be useful for medical applications where the robots are tasked with moving inside the human body. Here we cover the entire process of developing small-scale magnetic soft-bodied millirobots with multimodal locomotion capability, including robot design, material preparation, robot fabrication, locomotion control and locomotion optimization. We describe in detail the design, fabrication and control of a sheet-shaped soft millirobot with 12 different locomotion modes for traversing different terrains, an ephyra jellyfish-inspired soft millirobot that can manipulate objects in liquids through various swimming modes, a larval zebrafish-inspired soft millirobot that can adjust its body stiffness for efficient propulsion in different swimming speeds and a dual stimuli-responsive sheet-shaped soft millirobot that can switch its locomotion modes automatically by responding to changes in the environmental temperature. The procedure is aimed at users with basic expertise in soft robot development. The procedure requires from a few days to several weeks to complete, depending on the degree of characterization required.
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Affiliation(s)
- Ziyu Ren
- Physical Intelligence Department, Max Planck Institute for Intelligent Systems, Stuttgart, Germany
| | - Metin Sitti
- Physical Intelligence Department, Max Planck Institute for Intelligent Systems, Stuttgart, Germany.
- Institute for Biomedical Engineering, ETH Zurich, Zurich, Switzerland.
- School of Medicine and College of Engineering, Koç University, Istanbul, Turkey.
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Ma Z, Lu S, Wu Y, Zhang X, Wei Y, Mawignon FJ, Qin L, Shan L. Pressure-Activatable Liquid Metal Composites Flexible Sensor with Antifouling and Drag Reduction Functional Surface. ACS APPLIED MATERIALS & INTERFACES 2023; 15:54952-54965. [PMID: 37966900 DOI: 10.1021/acsami.3c12910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2023]
Abstract
Flexible sensors produced through three-dimensional (3D) printing have exhibited promising results in the context of underwater sensing detection (for applications in navigational vehicles and human activities). However, underwater vehicles and activities such as swimming and diving are highly susceptible to drag, which can cause negative impacts such as reduced speed and increased energy consumption. Additionally, microbial adhesion can shorten the service life of these vehicles. However, natural organisms are able to circumvent such problems, with shark skin offering excellent barrier properties and ruffled papillae providing effective protection against fouling. Here, we show that a sandwich system consisting of a spraying layer, conductive elastomer composite, and encapsulation layer can be printed for multifunctional integrated underwater sensors. The modulated viscoelastic properties of liquid metal form the foundation for printing features, while its pressure-activated properties offer the potential for switchable sensors. An integrated drag reduction and antifouling layer were created by combining the shark skin surface shield scale structure with the lotus leaf surface papillae structure. A 3D-printed flexible sensor was designed using our approach to monitor attitude changes and strain in underwater environments, showcasing its capabilities. Our printed sensors can reduce biological attachment density by more than 50% and reduce underwater drag by 8.6-10.3%.
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Affiliation(s)
- Zeyu Ma
- Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Shan Lu
- Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Yuhao Wu
- Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Xiaodong Zhang
- Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Yufan Wei
- Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Fagla Jules Mawignon
- Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Liguo Qin
- Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049, P. R. China
| | - Lei Shan
- AVIC Xi'an Flight Automatic Control Research Institute, Xi'an 710065, P. R. China
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Sun Y, Wang L, Zhu Z, Li X, Sun H, Zhao Y, Peng C, Liu J, Zhang S, Li M. A 3D-Printed Ferromagnetic Liquid Crystal Elastomer with Programmed Dual-Anisotropy and Multi-Responsiveness. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2302824. [PMID: 37437184 DOI: 10.1002/adma.202302824] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 07/06/2023] [Accepted: 07/11/2023] [Indexed: 07/14/2023]
Abstract
Liquid crystal elastomers (LCE) and magnetic soft materials are promising active materials in many emerging fields, such as soft robotics. Despite the high demand for developing active materials that combine the advantages of LCE and magnetic actuation, the lack of independent programming of the LCE nematic order and magnetization in a single material still hinders the desired multi-responsiveness. In this study, a ferromagnetic LCE (magLCE) ink with nematic order and magnetization is developed that can be independently programmed to be anisotropic, referred to as "dual anisotropy", via a customized 3D-printing platform. The magLCE ink is fabricated by dispersing ferromagnetic microparticles in the LCE matrix, and a 3D-printing platform is created by integrating a magnet with 3-DoF motion into an extrusion-based 3D printer. In addition to magnetic fields, magLCEs can also be actuated by heating sources (either environmental heating or photo-heating of the embedded ferromagnetic microparticles) with a high energy density and tunable actuation temperature. A programmed magLCE strip robot is demonstrated with enhanced adaptability to complex environments (different terrains, magnetic fields, and temperatures) using a multi-actuation strategy. The magLCE also has potential applications in mechanical memory, as demonstrated by the multistable mechanical metastructure array with remote writability and stable memory.
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Affiliation(s)
- Yuxuan Sun
- Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, 230026, P. R. China
| | - Liu Wang
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui, 230026, P. R. China
- State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Science, 15 Beisihuan West Road, Beijing, 100190, P. R. China
| | - Zhengqing Zhu
- Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, 230026, P. R. China
| | - Xingxiang Li
- Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, 230026, P. R. China
| | - Hong Sun
- Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, 230026, P. R. China
| | - Yong Zhao
- Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, 230026, P. R. China
| | - Chenhui Peng
- Department of Physics, University of Science and Technology of China, Hefei, Anhui, 230026, P. R. China
| | - Ji Liu
- Department of Mechanical and Energy Engineering, Southern University of Science and Technology of China, Shenzhen, 518055, P. R. China
- Shenzhen Key Laboratory of Biomimetic Robotics and Intelligent Systems, Department of Mechanical and Energy Engineering, Southern University of Science and Technology, Shenzhen, 518055, P. R. China
- Shenzhen Key Laboratory of Intelligent Robotics and Flexible Manufacturing Systems, Southern University of Science and Technology, Shenzhen, 518055, P. R. China
- Guangdong Provincial Key Laboratory of Human-Augmentation and Rehabilitation Robotics in Universities, Southern University of Science and Technology, Shenzhen, 518055, P. R. China
| | - Shiwu Zhang
- Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, 230026, P. R. China
| | - Mujun Li
- Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei, 230026, P. R. China
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Zhang Z, Liu G, Li Z, Zhang W, Meng Q. Flexible tactile sensors with biomimetic microstructures: Mechanisms, fabrication, and applications. Adv Colloid Interface Sci 2023; 320:102988. [PMID: 37690330 DOI: 10.1016/j.cis.2023.102988] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 08/07/2023] [Accepted: 08/26/2023] [Indexed: 09/12/2023]
Abstract
In recent years, flexible devices have gained rapid development with great potential in daily life. As the core component of wearable devices, flexible tactile sensors are prized for their excellent properties such as lightweight, stretchable and foldable. Consequently, numerous high-performance sensors have been developed, along with an array of innovative fabrication processes. It has been recognized that the improvement of the single performance index for flexible tactile sensors is not enough for practical sensing applications. Therefore, balancing and optimization of overall performance of the sensor are extensively anticipated. Furthermore, new functional characteristics are required for practical applications, such as freeze resistance, corrosion resistance, self-cleaning, and degradability. From a bionic perspective, the overall performance of a sensor can be optimized by constructing bionic microstructures which can deliver additional functional features. This review briefly summarizes the latest developments in bionic microstructures for different types of tactile sensors and critically analyzes the sensing performance of fabricated flexible tactile sensors. Based on this, the application prospects of bionic microstructure-based tactile sensors in human detection and human-machine interaction devices are introduced.
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Affiliation(s)
- Zhuoqing Zhang
- College of Bioresources Chemical and Materials Engineering, National Demonstration Center for Experimental Light Chemistry Engineering Education, Shaanxi University of Science and Technology, Xi'an 710021, People's Republic of China; Key Laboratory of Functional Printing and Transport Packaging of China National Light Industry, Key Laboratory of Paper-based Functional Materials of China National Light Industry, Shaanxi Provincial Key Laboratory of Papermaking Technology and Specialty Paper Development, Shaanxi University of Science and Technology, Xi'an 710021, People's Republic of China
| | - Guodong Liu
- College of Bioresources Chemical and Materials Engineering, National Demonstration Center for Experimental Light Chemistry Engineering Education, Shaanxi University of Science and Technology, Xi'an 710021, People's Republic of China; Key Laboratory of Functional Printing and Transport Packaging of China National Light Industry, Key Laboratory of Paper-based Functional Materials of China National Light Industry, Shaanxi Provincial Key Laboratory of Papermaking Technology and Specialty Paper Development, Shaanxi University of Science and Technology, Xi'an 710021, People's Republic of China.
| | - Zhijian Li
- College of Bioresources Chemical and Materials Engineering, National Demonstration Center for Experimental Light Chemistry Engineering Education, Shaanxi University of Science and Technology, Xi'an 710021, People's Republic of China; Key Laboratory of Functional Printing and Transport Packaging of China National Light Industry, Key Laboratory of Paper-based Functional Materials of China National Light Industry, Shaanxi Provincial Key Laboratory of Papermaking Technology and Specialty Paper Development, Shaanxi University of Science and Technology, Xi'an 710021, People's Republic of China
| | - Wenliang Zhang
- College of Bioresources Chemical and Materials Engineering, National Demonstration Center for Experimental Light Chemistry Engineering Education, Shaanxi University of Science and Technology, Xi'an 710021, People's Republic of China; Key Laboratory of Functional Printing and Transport Packaging of China National Light Industry, Key Laboratory of Paper-based Functional Materials of China National Light Industry, Shaanxi Provincial Key Laboratory of Papermaking Technology and Specialty Paper Development, Shaanxi University of Science and Technology, Xi'an 710021, People's Republic of China
| | - Qingjun Meng
- College of Bioresources Chemical and Materials Engineering, National Demonstration Center for Experimental Light Chemistry Engineering Education, Shaanxi University of Science and Technology, Xi'an 710021, People's Republic of China; Key Laboratory of Functional Printing and Transport Packaging of China National Light Industry, Key Laboratory of Paper-based Functional Materials of China National Light Industry, Shaanxi Provincial Key Laboratory of Papermaking Technology and Specialty Paper Development, Shaanxi University of Science and Technology, Xi'an 710021, People's Republic of China
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Slavkovic V, Palic N, Milenkovic S, Zivic F, Grujovic N. Thermo-Mechanical Characterization of 4D-Printed Biodegradable Shape-Memory Scaffolds Using Four-Axis 3D-Printing System. MATERIALS (BASEL, SWITZERLAND) 2023; 16:5186. [PMID: 37512458 PMCID: PMC10386114 DOI: 10.3390/ma16145186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 07/11/2023] [Accepted: 07/12/2023] [Indexed: 07/30/2023]
Abstract
This study was conducted on different models of biodegradable SMP (shape-memory polymer) scaffolds. A comparison was conducted utilizing a basic FDM (fused deposition modeling)/MEX (material extrusion) printer with a standard printing technique and a novel, modified, four-axis printing method with a PLA (poly lactic acid) polymer as the printing material. This way of making the 4D-printed BVS (biodegradable vascular stent) made it possible to achieve high-quality surfaces due to the difference in printing directions and improved mechanical properties-tensile testing showed a doubling in the elongation at break when using the four-axis-printed specimen compared to the regular printing, of 8.15 mm and 3.92 mm, respectfully. Furthermore, the supports created using this method exhibited a significant level of shape recovery following thermomechanical programming. In order to test the shape-memory effect, after the thermomechanical programming, two approaches were applied: one approach was to heat up the specimen after unloading it inside temperature chamber, and the other was to heat it in a warm bath. Both approaches led to an average recovery of the original height of 99.7%, while the in-chamber recovery time was longer (120 s) than the warm-bath recovery (~3 s) due to the more direct specimen heating in the latter case. This shows that 4D printing using the newly proposed four-axis printing is an effective, promising technique that can be used in the future to make biodegradable structures from SMP.
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Affiliation(s)
- Vukasin Slavkovic
- Faculty of Engineering, University of Kragujevac, 34000 Kragujevac, Serbia
| | - Nikola Palic
- Faculty of Engineering, University of Kragujevac, 34000 Kragujevac, Serbia
| | | | - Fatima Zivic
- Faculty of Engineering, University of Kragujevac, 34000 Kragujevac, Serbia
| | - Nenad Grujovic
- Faculty of Engineering, University of Kragujevac, 34000 Kragujevac, Serbia
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Romberg SK, Kotula AP. Simultaneous rheology and cure kinetics dictate thermal post-curing of thermoset composite resins for material extrusion. ADDITIVE MANUFACTURING 2023; 71:10.1016/j.addma.2023.103589. [PMID: 37427308 PMCID: PMC10327424 DOI: 10.1016/j.addma.2023.103589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
Thermoset composites are excellent candidates for material extrusion because they shear thin during extrusion but retain their shape once deposited via a yield stress. However, thermal post-curing is often required to solidify these materials, which can destabilize printed parts. Elevated temperatures can decrease the rheological properties responsible for stabilizing the printed structure before crosslinking solidifies the material. These properties, namely the storage modulus and yield stress, must therefore be characterized as a function of temperature and extent of reaction for various filler loadings. This work utilizes rheo-Raman spectroscopy to measure the storage modulus and dynamic yield stress as a function of temperature and conversion in epoxy-amine resins with fumed silica mass fractions up to 10 %. Both rheological properties are sensitive to conversion and particle loading, but only the dynamic yield stress is reduced by elevated temperatures early in the cure. Notably, the dynamic yield stress increases with conversion well before the chemical gel point. These findings motivate a two-step cure protocol that starts at a low temperature to mitigate the drop in dynamic yield stress, then ramps up to a high temperature when the dynamic yield stress is no longer at risk of decreasing to rapidly drive conversion to near completion. The results suggests that structural stability can be improved without resorting to increasing filler content, which limits control over the final properties, laying the groundwork for future studies to evaluate the stability improvements provided by the multi-step curing schedules.
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Affiliation(s)
- Stian K Romberg
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899
| | - Anthony P Kotula
- Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899
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