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Fused filament fabrication (FFF) is one of the low cost additive manufacturing (AM) techniques capable of printing complex design (both with commercial and non-commercial feedstock filaments by using different processing parameters). In this paper a comprehensive review has been prepared on FFF operating capabilities from thermoplastics material's view point. Various thermoplastic materials and composites available commercially and prepared at laboratory scale have been categorized based upon the reported studies performed (for thermal stability, mechanical properties etc.). It was observed that the nano composite based feed stock filament (prepared at lab scale) have edge over the micro-composites from thermo-mechanical properties view point. Further it has been noticed that the 3D printing is in changing phase and moving towards 4D printing of smart composites and designs. But hitherto little has been reported on printing of smart material with FFF platform. Further studies may be focused on printing of smart materials (both micro and nano composites) with FFF, as the low cost 3D printing solution in different engineering applications. [ABSTRACT FROM AUTHOR]

The poly-lactic acid (PLA), bio compatible polyamide (PA6) and TiO2 has established bio-medical applications especially in 3D printing of scaffolds. But hitherto little has been reported on improving the performance of multi-material matrix for PLA-PA6/TiO2 especially in 3D printing application of biomedical scaffolds. The anti-bacterial properties of PA6/TiO2 make it worthy to be explored with PLA matrix in multi layered fashion on the platform of fused deposition modeling (FDM) being low cost 3D printing technology for in house development of scaffolds. In this work an effort has been made for in-house development of feedstock filaments of PLA and PA6/TiO2 based polymeric composite matrix on twin screw extrusion (TSE) machine. Further the feedstock filament wires were used on FDM to establish the flexural, wear and morphological properties of multi-material 3D printed functional prototype. The results of the study suggest that for flexural strength, infill speed: 90mm/s; infill pattern: triangular and layer combination as 5 consecutive layers of PLA and 5 consecutive layers of PA6/TiO2 are the optimized conditions for FDM printing. The wear testing results suggest that the composite of PA6/TiO2 held low wear rate (823 µm) in comparison to PLA (wear rate: 1092 µm). Further porosity testing (based upon optical photomicrographs) at ×100 and fractured surface analysis at ×30 supported the observed trends for flexural and wear testing. The photomicrographs of fractured surface were 3D rendered to predict the role of surface roughness (Ra) profile for flexural properties. The mechanical and morphological observations are also supported with scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analysis. [ABSTRACT FROM AUTHOR]

This review highlights the additive manufacturing (AM) of smart materials, exhibiting 4-D properties under the affect of external stimulus. The smart materials are special in nature because they acquire different shapes, dimensional features (which may be altered a number of times in controlled fashion) when exposed to different external stimuli. Commercially, a number of smart materials are available that can be AM/3-D printed as metamaterials. Overall, this review outlines the applications of 3-D-printed material with 4-D properties for various applications (like biomedical, engineering, space science, structures, composites, etc.). A case study to evaluate the feasibility for in-house preparation of smart composite feedstock filament for fused deposition modelling-based 3-D printing has been presented for nonstructural engineering applications. The prepared filament in this case study has shown magnetic properties (which are considered essential for smart composite), so that when it may be triggered by external magnetic field to show 4-D behavior. [ABSTRACT FROM AUTHOR]

This article reports the comparison for mechanical and morphological properties of 3-D printed tensile specimen with fused deposition modeling by using multiblended and hybrid blended polylactic acid (PLA) matrix. The multiblended PLA matrix was 3-D printed as tensile specimen (as per American Society for Testing and Materials 638 type IV) comprising of 06 layers (01 layer PLA + 01 layer of PLA + polyvinyl chloride + 02 layers of PLA + wood powder + 02 layers of PLA + Fe3O4) each with layer thickness of 0.53 mm. The hybrid blended PLA matrix was also 3-D printed with similar dimensions and printing conditions. The composition/proportion of hybrid blended and multimaterial blended matrix has been selected on the basis of similar melt flow index (MFI) range and the final matrix was compared on basis of equal number of layers (06), similar rheological range (MFI: 40–45 g/10 min) and volume of product (same dimension of prototype). The results of study suggested that the 3-D printed functional prototype of multiblended PLA matrix has better mechanical and morphological properties than hybrid blended PLA matrix. The peak strength and break strength of hybrid blend-based prototype were observed to be 29.56 MPa and 26.60 MPa, respectively, whereas for the multimaterial-based functional prototypes, it was 46.28 MPa and 41.65 MPa, respectively. The results are also supported with scanning electron microscopy-based images, 3-D rendered images, and energy-dispersive X-ray analysis analysis. [ABSTRACT FROM AUTHOR]

In past two decades, the 3D printing of thermoplastic-based composite matrix has been widely explored for different engineering applications. But hitherto little has been reported on the preparation of polylactic acid (PLA) composite-based 3D-printed circular disc to ascertain its circumferential compressive strength, thermal conductivity, and morphological properties for possible structural engineering applications. The present investigation outlines the circumferential compressive strength, thermal conductivity, and morphological properties (Shore D hardness, surface voids using fractured surface analysis) of 3D-printed PLA composite matrix. Based upon the thermal conductivity test, it has been ascertained that sample printed on fused deposition modeling (FDM) setup with infill density of 100%, infill angle of 90°, and infill speed of 70 mm/s has shown maximum thermal conductivity (0.278 W/mK). Further it has been observed that with the increase in infill density, thermal conductivity of the sample has improved. Circumferential compressive testing has been performed on universal tensile testing machine setup (with in-house developed fixtures), and from printer setting optimization viewpoint, it has been ascertained that infill density has maximum contribution for peak and break strength. Further morphological studies (surface hardness, fractured surface analysis, and surface roughness (Ra) data) have supported the observed behavior of circumferential compressive strength and thermal conductivity of 3D-printed samples. [ABSTRACT FROM AUTHOR]

In recent past, fused deposition modeling (FDM)-based functional prototypes have been explored in printing of composites for 4-D applications as smart thermoplastics. The 3-D printed parts with 4-D properties have wide utility in structural/nonstructural engineering applications. Some studies have reported preparation of feedstock filament as composite material comprising of polylactic acid (PLA) reinforced with polyvinyl chloride (PVC), wood dust, and magnetite (Fe3O4). But hitherto very little has been reported on mechanical characterization of 3-D printed PLA-PVC-wood dust-Fe3O4 composite. The present work is an extension of study reported on mechanical and magnetic properties-based characterization of feedstock filament prepared for FDM, to understand the effect of processing parameters on properties of functional prototypes in structural/nonstructural engineering applications. For mechanical characterization, analysis of variance (ANOVA) and historical data approach have been used in optimization of 3-D printing condition in two stages. From ANOVA, it has been figured out that infill density of 100%, infill angle of 45°, and infill speed of 70 mm/s have given best result for peak strength and break strength in first stage. Further, the results of ANOVA model suggested that either there were some missing independent variables or interaction of present variables with each other was playing role in output. In second stage, historical data approach was used to understand the affect of interactions present among the input variables. The morphological analysis suggested that the sample printed with maximum density and low infill angle has minimum porosity and thus shows better mechanical properties. The results were supported with photomicrographs to understand the effect of porosity in the fractured sample. [ABSTRACT FROM AUTHOR]

In this study, a novel route for the preparation of feedstock filaments for fused deposition modelling from recycled high-density polyethylene (HDPE) and low-density polyethylene (LDPE) waste polymers has been explored. For improving the properties of HDPE/LDPE-recycled polymers, Fe powder has been reinforced through single-screw extrusion. It has been observed that Fe powder (from 0 wt% to 25 wt%) in the LDPE and HDPE matrices has shown increasing trend in melt flow index. Furthermore, Fe powder reinforcement resulted in 36.66% improvement in hardness of reinforced HDPE polymer and 64% in LDPE. Mechanical properties (peak elongation, peak strength, break strength and shore D hardness (SDH)) have been improved significantly with the addition of 6 wt% and 10 wt% reinforcement of Fe powder in the matrix of LDPE and HDPE, respectively. The results of study suggest that morphological properties, such as SDH and percentage porosity, have direct relation with mechanical properties as it has been found that the sample with better mechanical properties was also having high hardness and low porosity. Scanning electron microscopy and energy-dispersive X-ray spectroscopy have been performed on 3D printed functional parts and it has been observed that highly dense texture of HDPE and low surface roughness resulted in better mechanical properties. [ABSTRACT FROM AUTHOR]

The use of ferro/ferri/paramagnetic materials for self-assembly is quite common, but the use of superparamagnetic materials has not been explored for such applications. In the present study, polylactic acid (PLA) matrix has been reinforced with polyvinyl chloride (PVC), wood dust, and Fe3O4 particles (as superparamagnetic material) with twin screw extrusion (TSE) for the preparation of fused deposition modeling feedstock filament. The filament was tested for magnetic and mechanical properties whose results were analyzed and optimized for TSE parameters, and the regression model was used to find the effect of input parameters. The results of study suggest that the proportion as PLA 52.5 wt%, Fe3O4 25 wt%, PVC 15 wt%, and wood dust 7.5 wt% with TSE torque of 0.12 Nm, screw temperature of 165°C, and load of 5 kg are the optimized condition for the magnetization property. From vibration sample magnetometer analysis, it has been observed that all the samples having Fe3O4 in the matrix are of superparamagnetic character. Further, the magnetic and mechanical properties are not in correlation with each other for the blended samples which were counter verified by scanning electron microscopy and energy-dispersive spectroscopy analysis. [ABSTRACT FROM AUTHOR]

This paper reports the flexural, pull-out, and fractured surface characterization for multi-material three-dimensional printed functionally graded prototypes, which is prepared on fused deposition modeling setup. The work is an extension of previously reported study in which different thermoplastic matrices of polylactic acid blended with polyvinyl chloride, wood dust, and Fe3O4 powder (as multiple blended feedstock filaments) have been prepared separately with twin screw extrusion for possible three-dimensional printing. Finally, functionally graded prototypes with alternative layers of polylactic acid (01 layer), polylactic acid + polyvinyl chloride (01 layer), polylactic acid + wood dust (02 layers), and polylactic acid + Fe3O4 (02 layers) were three-dimensional printed on fused deposition modeling for flexural samples as per ASTM D790. With regard to process parameters of fused deposition modeling (in this case study), infill density of 100%, infill angle of 45°, and infill speed of 50 mm/s were the optimized processing conditions. The results of study suggest that maximum flexural strength 26.92 MPa and pull-out strength 18.11 MPa were observed for functionally graded multi-material three-dimensional printed prototypes. From fractured surface analysis and hardness result, it has been ascertained that higher infill density and lower infill angle lead to better diffusion of material in layer-by-layer fashion resulting into less void formation and better flexural and pull-out performances. The novelty of this work lies in accessing the behavior of three-dimensional printed prototypes having different functional ability for each layer, with a potential to replace hybrid blend-based prototypes. [ABSTRACT FROM AUTHOR]

Background- Extracorporeal membrane oxygenation (ECMO) has served for >2 decades as the standard of care for US children requiring mechanical support as a bridge to heart transplantation. Objective data on the safety and efficacy of ECMO for this indication are limited. We describe the outcomes of ECMO as a bridge to heart transplantation to serve as performance benchmarks for emerging miniaturized assist devices intended to replace ECMO. Methods and Results- Data from the Extracorporeal Life Support Organization Registry and the Organ Procurement Transplant Network database were merged to identify children supported with ECMO and listed for heart transplantation from 1994 to 2009. Independent predictors of wait-list and posttransplantation in-hospital mortality were identified. Objective performance goals for ECMO were developed. Of 773 children, the median age was 6 months (interquartile range, 1 to 44 months); 28% had cardiomyopathy; and in 38%, a bridge to transplantation was intended at ECMO initiation. Overall, 45% of subjects reached transplantation, although one third of those transplanted died before discharge; overall survival to hospital discharge was 47%. Wait-list mortality was independently associated with congenital heart disease, cardiopulmonary resuscitation before ECMO, and renal dysfunction. Posttransplantation mortality was associated with congenital heart disease, renal dysfunction, ECMO duration of >14 days, and initial ECMO indication as a bridge to recovery. In the objective performance goal cohort (n=485), patients with cardiomyopathy had the highest survival to hospital discharge (63%), followed by patients with myocarditis (59%), 2-ventricle congenital heart disease (44%) and 1-ventricle congenital heart disease (33%). Conclusion- Although ECMO is effective for short-term circulatory support, it is not reliable for the long-term circulatory support necessary for children awaiting heart transplantation. Fewer than half of patients bridged with ECMO survive to hospital discharge. More effective modalities for chronic circulatory support in children are urgently needed. [ABSTRACT FROM AUTHOR]

Reverse alignment (mirror image) visualization is a disconcerting situation occasionally faced during laparoscopic operations. This occurs when the camera faces back at the surgeon in the opposite direction from which the surgeon's body and instruments are facing. Most surgeons will attempt to optimize trocar and camera placement to avoid this situation. The authors' objective was to determine whether the intentional use of reverse alignment visualization during laparoscopic training would improve performance. A standard box trainer was configured for reverse alignment, and 34 medical students and junior surgical residents were randomized to train with either forward alignment (DIRECT) or reverse alignment (MIRROR) visualization. Enrollees were tested on both modalities before and after a 4-week structured training program specific to their modality. Student's t test was used to determine differences in task performance between the 2 groups. Twenty-one participants completed the study (10 DIRECT, 11 MIRROR). There were no significant differences in performance time between DIRECT or MIRROR participants during forward or reverse alignment initial testing. At final testing, DIRECT participants had improved times only in forward alignment performance; they demonstrated no significant improvement in reverse alignment performance. MIRROR participants had significant time improvement in both forward and reverse alignment performance at final testing. Reverse alignment imaging for laparoscopic training improves task performance for both reverse alignment and forward alignment tasks. This may be translated into improved performance in the operating room when faced with reverse alignment situations. Minimal lab training can account for drastic adaptation to this environment. [ABSTRACT FROM AUTHOR]

Background: It has been hypothesized that patients who are super-super morbidly obese, defined as having a body mass index (BMI) of 60 kg/m(2) or higher, have an increased rate of postoperative complications. As surgical techniques and operator experience with Roux-en-Y gastric bypass improved with time, the selection criteria have expanded to include the super-super morbidly obese. We hypothesize that a higher BMI does not predict a higher postoperative complication rate.Methods: The prospectively collected database for our Accredited Bariatric Program was queried for all laparoscopic Roux-en-Y gastric bypass procedures performed between January 2004 and July 2006. All cases were performed by a single surgeon at a tertiary-care center. Average postoperative follow-up time was 1 year. Patients were stratified into two groups: BMI < 60 kg/m(2) and BMI >or= 60 kg/m(2). The number of postoperative complications was compared between the two groups using a chi-square method with Yates correction.Results: One hundred and sixty-nine patients with adequate follow-up data were identified during the study period. Of these, 148 patients had BMI < 60 kg/m(2) (group 1) and 21 had BMI >or= 60 kg/m(2) (group 2). There were 28 (19%) total complications in group 1, and 4 (19%) total complications in group 2. There was no statistical difference between the two groups (p = 0.98). Stricture rate was 10% in group 1 and 5% in group 2.Conclusion: Patients with BMI >or= 60 kg/m(2) do not have a higher postoperative morbidity compared with other patients undergoing laparoscopic Roux-en-Y gastric bypass. The stricture rate is less in patients with BMI >or= 60 kg/m(2) compared with other patients. Longer follow-up is required to detect complications that occur after 1 year. Our study shows that laparoscopic Roux-en-Y gastric bypass can be safely performed on the super-supermorbidly obese. [ABSTRACT FROM AUTHOR]