Porosity is a major quality issue in additively manufactured (AM) materials due to improper selection of raw material or process parameters. While porosity is kept to a minimum for structural applications, parts with intentional (engineered) porosity find applications in prosthetics, sound dampeners & mufflers, catalytic converters, electrodes, heat exchangers, filters, etc. During post-processing of additive manufactured components using secondary machining to obtain required dimensional tolerance and/or surface quality, part porosity could lead to fluctuating cutting forces and reduced tool life. The machinability of the porous AM material is poor compared to the homogenous wrought material due to the intermittent cutting and anisotropy of AM materials. The cutting parameters for machining are generally optimized for continuous wrought material and are not applicable for porous AM material. Micromilling experiments were carried out on AM Ti6Al4V alloy with different porosity levels and cutting speed using a 1 mm diameter end mill. The progression of tool wear and associated mechanisms during micro-milling of additive manufactured Ti6Al4V samples with different porosity levels are experimentally investigated. Insights into tool-workpiece interaction during micro-machining are obtained in cases where pore size could be comparable to the cutting tool diameter. This research could lead to efficient hybrid additive-subtractive manufacturing technologies with improved tool life and reduced costs.
{"title":"Effect of Porosity on Tool Wear During Micromachining of Additive Manufactured Titanium Alloy","authors":"V. Varghese, Soham Mujumdar","doi":"10.1115/msec2022-80096","DOIUrl":"https://doi.org/10.1115/msec2022-80096","url":null,"abstract":"\u0000 Porosity is a major quality issue in additively manufactured (AM) materials due to improper selection of raw material or process parameters. While porosity is kept to a minimum for structural applications, parts with intentional (engineered) porosity find applications in prosthetics, sound dampeners & mufflers, catalytic converters, electrodes, heat exchangers, filters, etc. During post-processing of additive manufactured components using secondary machining to obtain required dimensional tolerance and/or surface quality, part porosity could lead to fluctuating cutting forces and reduced tool life. The machinability of the porous AM material is poor compared to the homogenous wrought material due to the intermittent cutting and anisotropy of AM materials. The cutting parameters for machining are generally optimized for continuous wrought material and are not applicable for porous AM material. Micromilling experiments were carried out on AM Ti6Al4V alloy with different porosity levels and cutting speed using a 1 mm diameter end mill. The progression of tool wear and associated mechanisms during micro-milling of additive manufactured Ti6Al4V samples with different porosity levels are experimentally investigated. Insights into tool-workpiece interaction during micro-machining are obtained in cases where pore size could be comparable to the cutting tool diameter. This research could lead to efficient hybrid additive-subtractive manufacturing technologies with improved tool life and reduced costs.","PeriodicalId":45459,"journal":{"name":"Journal of Micro and Nano-Manufacturing","volume":"31 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2022-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86911894","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Direct energy deposition (DED) has been widely used for additive manufacturing of metallic components toward a variety of applications. Surface characteristics of DED-fabricated components play key roles in determining the property and performance. Besides the average surface roughness which has been extensively investigated in literature, surface skewness and kurtosis are critical for surface integrity, particularly its durability due to stress concentration points. In this work, surface skewness and kurtosis of DED-fabricated 316L stainless steel as affected by processing parameters are investigated. In particular, the surface quality is measured using a microscopic structured light scanning (SLS) system, which is a relatively fast, low-cost, high-efficiency dimensional inspection metrology as compared to other methods. The results demonstrated the correlations between the printing parameters (laser power and scanning speed) and the surface topography of DED printed parts. It is found that the skewness and kurtosis of the surface are more sensitive to the change in scanning speed within a relatively low laser power range. Skewness is positively correlated with the scanning speed, while kurtosis shows a negative correlation with the scanning speed. Given a high scanning speed, Kurtosis and Skewness are more sensitive to the changes of scanning speed. Understanding the relationship between DED processing parameters and areal surface characteristics provides guidance and insights for process optimization and post-processing design towards additive manufacturing of high-performance metallic components.
{"title":"Real-Time Structured Light Scanning Characterization of Surface Topography of Direct Energy Deposited 316L Stainless Steel","authors":"Weijun Shen, Xing Zhang, Y. Liao, Beiwen Li","doi":"10.1115/msec2022-85783","DOIUrl":"https://doi.org/10.1115/msec2022-85783","url":null,"abstract":"\u0000 Direct energy deposition (DED) has been widely used for additive manufacturing of metallic components toward a variety of applications. Surface characteristics of DED-fabricated components play key roles in determining the property and performance. Besides the average surface roughness which has been extensively investigated in literature, surface skewness and kurtosis are critical for surface integrity, particularly its durability due to stress concentration points. In this work, surface skewness and kurtosis of DED-fabricated 316L stainless steel as affected by processing parameters are investigated. In particular, the surface quality is measured using a microscopic structured light scanning (SLS) system, which is a relatively fast, low-cost, high-efficiency dimensional inspection metrology as compared to other methods. The results demonstrated the correlations between the printing parameters (laser power and scanning speed) and the surface topography of DED printed parts. It is found that the skewness and kurtosis of the surface are more sensitive to the change in scanning speed within a relatively low laser power range. Skewness is positively correlated with the scanning speed, while kurtosis shows a negative correlation with the scanning speed. Given a high scanning speed, Kurtosis and Skewness are more sensitive to the changes of scanning speed. Understanding the relationship between DED processing parameters and areal surface characteristics provides guidance and insights for process optimization and post-processing design towards additive manufacturing of high-performance metallic components.","PeriodicalId":45459,"journal":{"name":"Journal of Micro and Nano-Manufacturing","volume":"16 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2022-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86179941","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The overarching goal of this research work is to synthesize and fabricate mechanically robust, dimensionally accurate, and porous bone scaffolds for the clinical treatment of osseous fractures, defects, and diseases. In pursuit of this goal, the objective of the work is to investigate the influence of hydroxyapatite (HA) as well as polysaccharide concentration on the mechanical properties of bone scaffolds, fabricated using freeze drying process. Freeze drying or lyophilization has emerged as a robust method for the fabrication of a broad spectrum of tissue constructs. Freeze Drying allows for multi-material fabrication of structures with complex pore morphology for soft and hard tissue engineering applications. However, the process is intrinsically complex; the complexity of the process, to a great extent, stems from complex physical phenomena (such as sublimation) as well as material-process interactions, which may adversely affect the mechanical properties, the surface morphology, and ultimately the functional characteristics of fabricated bone scaffolds. Consequently, physics-based process and material characterization would be an inevitable need. In this study, the influence of HA and polysaccharide concentration was investigated using a central composite design (CCD). The concentration of both HA and polysaccharide was changed in the range of 5%–15% with the aim to obtain mechanically robust structures. The compression properties of the fabricated bone scaffolds were measured using a compression testing machine. The outcomes of this study pave the way for the fabrication of complex, mechanically strong, and porous bone-like scaffolds with tunable medical and functional properties.
{"title":"Investigation of the Influence of Hydroxyapatite and Polysaccharide Concentration on the Mechanical Properties of Bone Scaffolds, Fabricated Using Freeze Drying Process","authors":"Tanner Ekstrom, James B. Day, Roozbeh Salary","doi":"10.1115/msec2022-85437","DOIUrl":"https://doi.org/10.1115/msec2022-85437","url":null,"abstract":"The overarching goal of this research work is to synthesize and fabricate mechanically robust, dimensionally accurate, and porous bone scaffolds for the clinical treatment of osseous fractures, defects, and diseases. In pursuit of this goal, the objective of the work is to investigate the influence of hydroxyapatite (HA) as well as polysaccharide concentration on the mechanical properties of bone scaffolds, fabricated using freeze drying process. Freeze drying or lyophilization has emerged as a robust method for the fabrication of a broad spectrum of tissue constructs. Freeze Drying allows for multi-material fabrication of structures with complex pore morphology for soft and hard tissue engineering applications. However, the process is intrinsically complex; the complexity of the process, to a great extent, stems from complex physical phenomena (such as sublimation) as well as material-process interactions, which may adversely affect the mechanical properties, the surface morphology, and ultimately the functional characteristics of fabricated bone scaffolds. Consequently, physics-based process and material characterization would be an inevitable need. In this study, the influence of HA and polysaccharide concentration was investigated using a central composite design (CCD). The concentration of both HA and polysaccharide was changed in the range of 5%–15% with the aim to obtain mechanically robust structures. The compression properties of the fabricated bone scaffolds were measured using a compression testing machine. The outcomes of this study pave the way for the fabrication of complex, mechanically strong, and porous bone-like scaffolds with tunable medical and functional properties.","PeriodicalId":45459,"journal":{"name":"Journal of Micro and Nano-Manufacturing","volume":"12 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2022-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85246510","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Copper (Cu) and Tin (Sn) were low-pressure cold sprayed onto polyamide 6 (PA 6) and polypropylene (PP) substrates. The first layer of Sn and Cu was built onto the polymer substrate and continued as an alternative layer of Cu and Sn build-up under controlled process parameters. The chronological order of either first spraying Cu or Sn does not hinder building a coated layer on the PA 6 and PP substrate. The coating thickness can reach as thick as 100 μm of the PA 6 (Cu/Sn/Cu) layer. Results show the potential ability for additive manufacturing using polymeric templates. The cold spray kinetic bonding of the metals avoids any intermediate phase formation. The mechanical performance of the coated material remains the same as the deposition process does not degrade bulk substrates. The contour of the interface and the surface roughness resulting from the cold spray coating process lead to a deformed surface layer of the polymer on the particle size of the powder used for cold spraying. While the metallic coating deforms via plastic deformation and cracking, the through-thickness cracks, which primarily are perpendicular to the loading direction, do not span the width of the coating due to the tortuous nature of the microstructure. The advantage provides electrical conductivity to strains of up to 10% and maintains a low electrical resistance.
{"title":"Cold Spray Multilayer Metal Build-Up on a Polymeric Substrate","authors":"J. Tsai, M. Jun, D. Bahr","doi":"10.1115/msec2022-80318","DOIUrl":"https://doi.org/10.1115/msec2022-80318","url":null,"abstract":"\u0000 Copper (Cu) and Tin (Sn) were low-pressure cold sprayed onto polyamide 6 (PA 6) and polypropylene (PP) substrates. The first layer of Sn and Cu was built onto the polymer substrate and continued as an alternative layer of Cu and Sn build-up under controlled process parameters. The chronological order of either first spraying Cu or Sn does not hinder building a coated layer on the PA 6 and PP substrate. The coating thickness can reach as thick as 100 μm of the PA 6 (Cu/Sn/Cu) layer. Results show the potential ability for additive manufacturing using polymeric templates. The cold spray kinetic bonding of the metals avoids any intermediate phase formation. The mechanical performance of the coated material remains the same as the deposition process does not degrade bulk substrates. The contour of the interface and the surface roughness resulting from the cold spray coating process lead to a deformed surface layer of the polymer on the particle size of the powder used for cold spraying. While the metallic coating deforms via plastic deformation and cracking, the through-thickness cracks, which primarily are perpendicular to the loading direction, do not span the width of the coating due to the tortuous nature of the microstructure. The advantage provides electrical conductivity to strains of up to 10% and maintains a low electrical resistance.","PeriodicalId":45459,"journal":{"name":"Journal of Micro and Nano-Manufacturing","volume":"24 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2022-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84794783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yujie Shan, Aravind Krishnakumar, Zehan Qin, Huachao Mao
Real-time and in-situ printing performance diagnostic in vat photopolymerization is critical to control printing quality, improve process reliability, and reduce wasted time and materials. This paper proposed a low-cost smart resin vat to monitor the printing process and detect the printing faults. Built on a conventional vat photopolymerization process, we added equally spaced thermistors along the edges of the resin vat. During printing, polymerization heat transferred to the edges of the resin vat, which increased thermistors’ temperature and enhanced resistances. The heat flux received at each thermistor varied with the distance to the place of photopolymerization. The temperature profiles of all thermistors were determined by the curing image pattern in each layer, and vice versa. Machine learning algorithms were leveraged to infer the printing status from the measured temperatures of these thermistors. Specifically, we proposed a simple and robust Failure Index to detect if the printing was active or terminated. Gaussian process regression was utilized to predict the printing area using the temperature recordings within a layer. The model was trained, validated, and tested using the data set collected by printing six parts. Different printing abnormalities, including printing failures, manual printing pause, and missing features (incorrect printing area), were successfully detected. The proposed approach modified the resin vat only and could be easily applied to all vat photopolymerization processes, including SLA, DLP, and LCD based 3D printing. The limitation and future work are also highlighted.
{"title":"Smart Resin Vat: Real-Time Detecting Failures, Defects, and Curing Area in Vat Photopolymerization 3D Printing","authors":"Yujie Shan, Aravind Krishnakumar, Zehan Qin, Huachao Mao","doi":"10.1115/msec2022-85691","DOIUrl":"https://doi.org/10.1115/msec2022-85691","url":null,"abstract":"\u0000 Real-time and in-situ printing performance diagnostic in vat photopolymerization is critical to control printing quality, improve process reliability, and reduce wasted time and materials. This paper proposed a low-cost smart resin vat to monitor the printing process and detect the printing faults. Built on a conventional vat photopolymerization process, we added equally spaced thermistors along the edges of the resin vat. During printing, polymerization heat transferred to the edges of the resin vat, which increased thermistors’ temperature and enhanced resistances. The heat flux received at each thermistor varied with the distance to the place of photopolymerization. The temperature profiles of all thermistors were determined by the curing image pattern in each layer, and vice versa. Machine learning algorithms were leveraged to infer the printing status from the measured temperatures of these thermistors. Specifically, we proposed a simple and robust Failure Index to detect if the printing was active or terminated. Gaussian process regression was utilized to predict the printing area using the temperature recordings within a layer. The model was trained, validated, and tested using the data set collected by printing six parts. Different printing abnormalities, including printing failures, manual printing pause, and missing features (incorrect printing area), were successfully detected. The proposed approach modified the resin vat only and could be easily applied to all vat photopolymerization processes, including SLA, DLP, and LCD based 3D printing. The limitation and future work are also highlighted.","PeriodicalId":45459,"journal":{"name":"Journal of Micro and Nano-Manufacturing","volume":"14 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2022-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78764449","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ishrat Jahan Biswas, Enrique Contreras Lopez, F. Ahmed, Jianzhi Li
Laser direct writing (LDW) is a fast and cost-effective method for printing conductive patterns in flexible polymer substrates. The electrical, chemical, and mechanical properties of polyimide (PI) make it an attractive material choice for laser writing of conductive circuits in such polymer. Electrically insulating PI has shown great potential for flexible printed electronics as LDW enables selective carbonization in the bulk of such material leading to the formation of conductive lines. However, existing studies in this area reveal a few key limitations of this approach including limited conductivity of written structures and fragility of carbonized PI. Therefore, more research is required to overcome those limitations and reap the benefits of the LDW approach in writing flexible electronic circuits in PI. The proposed study investigates potential approaches to enhance the electrical conductivity of femtosecond laser written bulk carbon structures in PI films. Deposition of laser energy was varied by changing key process parameters such as pulse energy, pulse picker divider, and hatch distance of laser scan to maximize the conductively of the carbon structure. The experimental findings show a strong dependency of laser energy deposition on the conductivity carbon structures in PI films. To further enhance the electrical conductivity of laser written structures, the feasibility of adding copper microparticles to the PI solution and subsequent laser carbonization was studied. The proposed LDW of conductive lines has potential in flexible electronic circuits and sensing applications.
{"title":"Ultrafast Laser Direct Writing of Conductive Patterns on Polyimide Substrate","authors":"Ishrat Jahan Biswas, Enrique Contreras Lopez, F. Ahmed, Jianzhi Li","doi":"10.1115/msec2022-85684","DOIUrl":"https://doi.org/10.1115/msec2022-85684","url":null,"abstract":"\u0000 Laser direct writing (LDW) is a fast and cost-effective method for printing conductive patterns in flexible polymer substrates. The electrical, chemical, and mechanical properties of polyimide (PI) make it an attractive material choice for laser writing of conductive circuits in such polymer. Electrically insulating PI has shown great potential for flexible printed electronics as LDW enables selective carbonization in the bulk of such material leading to the formation of conductive lines. However, existing studies in this area reveal a few key limitations of this approach including limited conductivity of written structures and fragility of carbonized PI. Therefore, more research is required to overcome those limitations and reap the benefits of the LDW approach in writing flexible electronic circuits in PI. The proposed study investigates potential approaches to enhance the electrical conductivity of femtosecond laser written bulk carbon structures in PI films. Deposition of laser energy was varied by changing key process parameters such as pulse energy, pulse picker divider, and hatch distance of laser scan to maximize the conductively of the carbon structure. The experimental findings show a strong dependency of laser energy deposition on the conductivity carbon structures in PI films. To further enhance the electrical conductivity of laser written structures, the feasibility of adding copper microparticles to the PI solution and subsequent laser carbonization was studied. The proposed LDW of conductive lines has potential in flexible electronic circuits and sensing applications.","PeriodicalId":45459,"journal":{"name":"Journal of Micro and Nano-Manufacturing","volume":"20 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2022-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78091340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nearly 1 in 4 women undergo surgery for pelvic organ prolapse or urinary incontinence in the US. The weakened pelvic floor, which could be caused by childbirth injury, aging, or obesity, fails to support the pelvic organs, resulting in urinary incontinence, sexual difficulties, and pelvic organ prolapse (POP). Polypropylene (PP) meshes are often used in reconstructive surgeries as a reinforcement to provide long-term, durable support. However, commercial polypropylene meshes have a risk of complications, such as pain, mesh erosion, and infection. The United States Food and Drug Administration (FDA) has consequently re-classified the polypropylene mesh as a high-risk device. Therefore, the need for new meshes to cure POP with a rapid prototyping technique is urgent, especially for personalized medicine. Therefore, we developed a new implantable mesh using biocompatible polymers (e.g., gelatin, polyvinyl alcohol (PVA), chitosan) with controlled bonding strength and tunable lifetime. Our group has leveraged additive manufacturing for porous scaffold structures beneficial for cell attachment and nutrition transmission. Our POP scaffold mesh has demonstrated high biocompatibility and controlled biodegradability. We will also leverage our manufacturing expertise and clinical partnerships to examine cell proliferation and differentiation for tissue regeneration. Our advanced manufacturing method is compatible with other materials and has potential use in layered structures for dental, heart, or bone engineering applications.
{"title":"3D Printed Pelvic Organ Prolapse (POP) Tissue Scaffolds","authors":"Yuxiang Zhu, Dharneedar Ravichandran, Kenan Song","doi":"10.1115/msec2022-85062","DOIUrl":"https://doi.org/10.1115/msec2022-85062","url":null,"abstract":"\u0000 Nearly 1 in 4 women undergo surgery for pelvic organ prolapse or urinary incontinence in the US. The weakened pelvic floor, which could be caused by childbirth injury, aging, or obesity, fails to support the pelvic organs, resulting in urinary incontinence, sexual difficulties, and pelvic organ prolapse (POP). Polypropylene (PP) meshes are often used in reconstructive surgeries as a reinforcement to provide long-term, durable support. However, commercial polypropylene meshes have a risk of complications, such as pain, mesh erosion, and infection. The United States Food and Drug Administration (FDA) has consequently re-classified the polypropylene mesh as a high-risk device. Therefore, the need for new meshes to cure POP with a rapid prototyping technique is urgent, especially for personalized medicine.\u0000 Therefore, we developed a new implantable mesh using biocompatible polymers (e.g., gelatin, polyvinyl alcohol (PVA), chitosan) with controlled bonding strength and tunable lifetime. Our group has leveraged additive manufacturing for porous scaffold structures beneficial for cell attachment and nutrition transmission. Our POP scaffold mesh has demonstrated high biocompatibility and controlled biodegradability. We will also leverage our manufacturing expertise and clinical partnerships to examine cell proliferation and differentiation for tissue regeneration. Our advanced manufacturing method is compatible with other materials and has potential use in layered structures for dental, heart, or bone engineering applications.","PeriodicalId":45459,"journal":{"name":"Journal of Micro and Nano-Manufacturing","volume":"7 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2022-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90215629","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hydrothermal-assisted jet fusion (HJF) process is a new additive manufacturing (AM) method for ceramics, which is capable of fabricating ceramic 3D structures without the need for organic binders. The HJF process selectively deposits a water-based solution into a ceramic powder bed in a layer-by-layer manner and fuses particles together through a hydrothermal mechanism. Since no organic binder is used in the HJF process, such a binder-free AM method can produce ceramic parts with less energy consumed for binder removal and has the potential to reach the material’s theoretical properties such as full density and exceptional mechanical strength. Nevertheless, the fabricated parts by the HJF process still suffers from issues, such as over fusion base-layer damage, pattern shifting, etc. In this paper, the effects of process parameters (e.g., stroke, droplet size, press number, final press, etc.) on the fabrication quality (e.g., diffusion behavior of deposited inks and shape fidelity of the fabricated parts, etc.) of the HJF process are studied. Optimum process settings are identified to alleviate those quality issues, and 3D structures with high shape fidelity were successfully fabricated to highlight the capability of the HJF process in achieving ceramic 3D structures with high accuracy and high performance.
{"title":"Process Optimization for Hydrothermal-Assisted Jet Fusion Additive Manufacturing of Ceramics","authors":"F. Fei, L. Kirby, Xuan Song","doi":"10.1115/msec2022-85772","DOIUrl":"https://doi.org/10.1115/msec2022-85772","url":null,"abstract":"\u0000 Hydrothermal-assisted jet fusion (HJF) process is a new additive manufacturing (AM) method for ceramics, which is capable of fabricating ceramic 3D structures without the need for organic binders. The HJF process selectively deposits a water-based solution into a ceramic powder bed in a layer-by-layer manner and fuses particles together through a hydrothermal mechanism. Since no organic binder is used in the HJF process, such a binder-free AM method can produce ceramic parts with less energy consumed for binder removal and has the potential to reach the material’s theoretical properties such as full density and exceptional mechanical strength. Nevertheless, the fabricated parts by the HJF process still suffers from issues, such as over fusion base-layer damage, pattern shifting, etc. In this paper, the effects of process parameters (e.g., stroke, droplet size, press number, final press, etc.) on the fabrication quality (e.g., diffusion behavior of deposited inks and shape fidelity of the fabricated parts, etc.) of the HJF process are studied. Optimum process settings are identified to alleviate those quality issues, and 3D structures with high shape fidelity were successfully fabricated to highlight the capability of the HJF process in achieving ceramic 3D structures with high accuracy and high performance.","PeriodicalId":45459,"journal":{"name":"Journal of Micro and Nano-Manufacturing","volume":"74 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2022-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88344954","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Two-photon lithography (TPL) is a photopolymerization-based additive manufacturing technique capable of fabricating complex 3D structures with submicron features. Projection TPL (P-TPL) is a specific implementation that leverages projection-based parallelization to increase the rate of printing by three orders of magnitude. However, a practical limitation of P-TPL is the high shrinkage of the printed microstructures that is caused by the relatively low degree of polymerization in the as-printed parts. Unlike traditional stereolithography (SLA) methods and conventional TPL, most of the polymerization in P-TPL occurs through dark reactions while the light source is off, thereby resulting in a lower degree of polymerization. In this study, we empirically investigated the parameters of the P-TPL process that affect shrinkage. We observed that the shrinkage reduces with an increase in the duration of laser exposure and with a reduction of layer spacing. To broaden the design space, we explored a photochemical post-processing technique that involves further curing the printed structures using UV light while submerging them in a solution of a photoinitiator. With this post-processing, we were able to reduce the areal shrinkage from more than 45% to 1% without limiting the geometric design space. This shows that P-TPL can achieve high dimensional accuracy while taking advantage of the high throughput when compared to conventional serial TPL. Furthermore, P-TPL has a higher resolution when compared to the conventional SLA prints at a similar shrinkage rate.
{"title":"Minimizing Shrinkage in Microstructures Printed With Projection Two-Photon Lithography","authors":"Harnjoo Kim, S. Saha","doi":"10.1115/msec2022-86076","DOIUrl":"https://doi.org/10.1115/msec2022-86076","url":null,"abstract":"\u0000 Two-photon lithography (TPL) is a photopolymerization-based additive manufacturing technique capable of fabricating complex 3D structures with submicron features. Projection TPL (P-TPL) is a specific implementation that leverages projection-based parallelization to increase the rate of printing by three orders of magnitude. However, a practical limitation of P-TPL is the high shrinkage of the printed microstructures that is caused by the relatively low degree of polymerization in the as-printed parts. Unlike traditional stereolithography (SLA) methods and conventional TPL, most of the polymerization in P-TPL occurs through dark reactions while the light source is off, thereby resulting in a lower degree of polymerization. In this study, we empirically investigated the parameters of the P-TPL process that affect shrinkage. We observed that the shrinkage reduces with an increase in the duration of laser exposure and with a reduction of layer spacing. To broaden the design space, we explored a photochemical post-processing technique that involves further curing the printed structures using UV light while submerging them in a solution of a photoinitiator. With this post-processing, we were able to reduce the areal shrinkage from more than 45% to 1% without limiting the geometric design space. This shows that P-TPL can achieve high dimensional accuracy while taking advantage of the high throughput when compared to conventional serial TPL. Furthermore, P-TPL has a higher resolution when compared to the conventional SLA prints at a similar shrinkage rate.","PeriodicalId":45459,"journal":{"name":"Journal of Micro and Nano-Manufacturing","volume":"24 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2022-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74803243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Composite and hybrid materials displaying layered structures have broad applications in structural composites, fire retardant barriers, tissue scaffolds, and microelectronics. Inspired by biosystems, in this study, we explore the invention of a new 3D printing principle that can produce layered structures similar to those in trees, overcoming the bottleneck in additive manufacturing to include multi-materials. We use polyvinyl alcohol (PVA) and carbon nanotubes (CNTs) as material examples for producing alternating layers. With the unique 3D printing platform, Multiphase Direct Ink Writing (MDIW), the optimized dispersion quality and rheology behaviors allow the number of layers within an individual printing line to change between 4 and 512 layers. The mechanical tests consistently increased young’s modulus and ultimate tensile strength with decreased layer thickness and dispersion quality. The best-performed composites have 128 layers in one printing line, beyond which the dispersion of CNTs deteriorated due to aggregates. Due to the thin layer thickness, the improved composite mechanics relate to the closely packed CNTs and their alignment. Moreover, we will also demonstrate this MDIW printing with different polymers (e.g., thermoplastic urethane and polylactic acid) and nanoparticles (e.g., iron oxide, carbon fibers) for mechanical enhancement and intelligent behaviors. This research demonstrated one new 3D printing method, MDIW, that can fabricate multilayered composites containing well-managed content in each layer. Our advanced manufacturing method is compatible with other materials and has potential use in batteries, supercapacitors, solar cells, regenerative medicine, and energetic systems requiring layered structures.
{"title":"One-Step 3D Printed Layers Along With xy-in Plane Directions for Enhanced Multifunctional Nanocomposites","authors":"Dharneedar Ravichandran, Kenan Song","doi":"10.1115/msec2022-85056","DOIUrl":"https://doi.org/10.1115/msec2022-85056","url":null,"abstract":"\u0000 Composite and hybrid materials displaying layered structures have broad applications in structural composites, fire retardant barriers, tissue scaffolds, and microelectronics. Inspired by biosystems, in this study, we explore the invention of a new 3D printing principle that can produce layered structures similar to those in trees, overcoming the bottleneck in additive manufacturing to include multi-materials. We use polyvinyl alcohol (PVA) and carbon nanotubes (CNTs) as material examples for producing alternating layers. With the unique 3D printing platform, Multiphase Direct Ink Writing (MDIW), the optimized dispersion quality and rheology behaviors allow the number of layers within an individual printing line to change between 4 and 512 layers. The mechanical tests consistently increased young’s modulus and ultimate tensile strength with decreased layer thickness and dispersion quality. The best-performed composites have 128 layers in one printing line, beyond which the dispersion of CNTs deteriorated due to aggregates. Due to the thin layer thickness, the improved composite mechanics relate to the closely packed CNTs and their alignment.\u0000 Moreover, we will also demonstrate this MDIW printing with different polymers (e.g., thermoplastic urethane and polylactic acid) and nanoparticles (e.g., iron oxide, carbon fibers) for mechanical enhancement and intelligent behaviors. This research demonstrated one new 3D printing method, MDIW, that can fabricate multilayered composites containing well-managed content in each layer. Our advanced manufacturing method is compatible with other materials and has potential use in batteries, supercapacitors, solar cells, regenerative medicine, and energetic systems requiring layered structures.","PeriodicalId":45459,"journal":{"name":"Journal of Micro and Nano-Manufacturing","volume":"60 1","pages":""},"PeriodicalIF":1.0,"publicationDate":"2022-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89172415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：