Polyactic Acid Research Articles

Microbial community acclimatization enhances bioplastics biodegradation and biogas production under thermophilic anaerobic digestion

This paper reports the results of a novel study of microbial acclimatization for bioplastics anaerobic degradation and conversion into biogas. Three sequential anaerobic digestion (AD) runs were carried out to favour microbial acclimatization to two different bioplastics, starch-based (SBS) and polyactic-acid (PLA).AD of SBS and PLA bioplastics was favoured by the acclimatization of the inoculum to the substrate after each run of AD. SBS conversion into biogas increased by 52 % (from 94 to 143 NL kgVS-1) and it was correlated with the enhanced growth of starch degrading bacteria such as Hydrogenispora, Halocella and Haloplasma. PLA anaerobic degradation increased by 97 % (from 395 to 779 NLbiogas kgVS-1) and it was related to the acclimatization of known PLA-degraders such as Tepidimicrobium, Methanothermobacter and Tepidanaerobacter. Microbial acclimatization appears a suitable and low-cost strategy to enhance bioplastics circularity by promoting their anaerobic biodegradation and conversion into biogas.

Anatomically Realistic 3D Printed Mouse Phantom for Multi-Institutional Benchmarking of FLASH and CONV Irradiation

It is reported that about US$28B/year is spent on pre-clinical studies that are not reproducible. FLASH studies may suffer from the same reproducibility crisis due to the non-standard nature of the FLASH beamlines and the lack of dosimeters that can function at ultra-high dose-rates. There have been reports of different outcomes with regard to the FLASH effect across different institutions, even though similar beamlines, temporal structure, and nominal dose levels were used. This brings up the question of the accuracy of dosimetry under FLASH conditions for a fair comparison between FLASH and CONV. To answer this question, we develop and characterize an anatomically realistic 3D-printed mouse phantom to be used in a multi-institutional dosimetric benchmarking effort. Mesh files for bony anatomy, lungs, and soft tissue derived from a CT scan of a mouse were converted to an editable 3D model. The 3D model was cut along the coronal plane and modified to allow the inclusion of radiographic film. A multi-material approach was employed to print the phantom. A dual-nozzle 3D printer was used, where one of the nozzles used Acrylonitrile butadiene styrene (ABS) to mimic soft tissue and the other nozzle used Polyactic acid (PLA) to mimic bone density. The two materials were used together in a single print. Lungs were approximated by lightweight PLA and were printed separately and inserted into corresponding cavities in the phantom. Hounsfield Units (HU) and print-to-print stability were verified. Radiographic films were laser cut for different anatomical sites. Two institutes took part in this study with data pending from 3 more institutions. The institutes were instructed to deliver 10 Gy to the plane of the film for the whole abdomen, whole lung, and brain irradiations. 2D dose maps were compared between FLASH and CONV, and the deviation from the prescribed dose was also measured. The 3D-printed soft tissue, bone, and lung densities were measured to be ∼ 1.01 g/cc, 1.22 g/cc, and 0.44 g/cc, respectively. For soft tissue and bone, the Hounsfield unit (HU) difference from one print to another was < 10 HU. The greatest variation was within the lungs (54 HU), but this had a minimal effect on the dose distribution (<1%). For the two institutions that completed the survey, the maximum average difference between FLASH and CONV for all irradiations was 0.75 Gy (7.48%). The maximum average difference from the prescribed dose for all irradiations was 0.7 Gy (7.20%) across both institutions. The largest discrepancy was generally observed to be for lung irradiation, indicating that lack of treatment planning systems limits our ability to prescribe accurately in areas of inhomogeneities. A 3D printed anatomically realistic mouse phantom was developed, characterized, and used in a multi-institutional dosimetric benchmarking effort. Such a study is paramount for the clinical translation of FLASH as it facilitates reduced variability from one institution to another.

The High‐Strength, Flexible Organic Solvent Driven Reversible “Deformation‐Recovery‐Reverse Deformation” Responsive g‐PLA/PPC/PVA Film for Contactless Actuation

AbstractThe non‐contact deformation response driven by organic solvent has potential applications in the fields of intelligent devices, soft robots, sensing detection, and biomedical micro‐devices. The modified polyactic acid (g‐PLA)/polypropyl carbonate (PPC)/polyvinyl alcohol (PVA) sandwich with deformation response film is prepared by the asymmetric swelling response mechanism. Specially, the flexible sandwich film achieves the non‐contact driving response of “deformation‐recovery‐reverse deformation”, showing excellent deformation performance. The curvature of sandwich film reaches 13.79 cm−1 within 15 s, and the film recovers to its initial state within 3 s, then the curvature of the reverse coil reaches 18.18 cm−1 within 15 s and finally achieves a stable state. This special phenomenon is caused by the different adsorption swelling and desorption rates of volatile organic solvents in g‐PLA, PPC, and PVA layers. Additionally, the flexible film has high strength, reversible circulation, and stable actuation performance. The application scenarios of the bionic flower actuator, artificial octopus, intelligent protective cover, and transportable objects are successfully implemented. This work will significantly provide substantial guidance for the development of intelligent driving technology in the future.

Design and CT imaging of casper, an anthropomorphic breathing thorax phantom

The goal of this work was to build an anthropomorphic thorax phantom capable of breathing motion with materials mimicking human tissues in x-ray imaging applications. The thorax phantom, named Casper, was composed of resin (body), foam (lungs), glow polyactic acid (bones) and natural polyactic acid (tumours placed in the lungs). X-ray attenuation properties of all materials prior to manufacturing were evaluated by means of photon-counting computed tomography (CT) imaging on a table-top system. Breathing motion was achieved by a scotch-yoke mechanism with diaphragm motion frequencies of 10−20 rpm and displacements of 1 to 2 cm. Casper was manufactured by means of 3D printing of moulds and ribs and assembled in a complex process. The final phantom was then scanned using a clinical CT scanner to evaluate material CT numbers and the extent of tumour motion. Casper CT numbers were close to human CT numbers for soft tissue (46 HU), ribs (125 HU), lungs (−840 HU) and tumours (−45 HU). For a 2 cm diaphragm displacement the largest tumour displacement was 0.7 cm. The five tumour volumes were accurately assessed in the static CT images with a mean absolute error of 4.3%. Tumour sizes were either underestimated for smaller tumours or overestimated for larger tumours in dynamic CT images due to motion blurring with a mean absolute difference from true volumes of 10.3%. More Casper information including a motion movie and manufacturing data can be downloaded from http://web.uvic.ca/~bazalova/Casper/.

Mechanical Properties of 3D-Printed Components Using Fused Deposition Modeling: Optimization Using the Desirability Approach and Machine Learning Regressor

The fused deposition modelling (FDM) technique involves the deposition of a fused layer of material according to the geometry designed in the software. Several parameters affect the quality of parts produced by FDM. This paper investigates the effect of FDM printing process parameters on tensile strength, impact strength, and flexural strength. The effects of process parameters such as printing speed, layer thickness, extrusion temperature, and infill percentage are studied. Polyactic acid (PLA) was used as a filament material for printing test specimens. The experimental layout is designed according to response surface methodology (RSM) and responses are collected. Specimens are prepared for testing of these parameters as per ASTM standards. A mathematical model for each of the responses is developed based on the nonlinear regression method. The desirability approach, nonlinear regression, as well as experimental values are in close agreement with each other. The desirability approach predicted the tensile strength, impact strength, and flexural strength with a less percentage error of 3.109, 6.532, and 3.712, respectively. The nonlinear regression approach predicted the tensile strength, impact strength, and flexural strength with a less percentage error of 2.977, 6.532, and 3.474, respectively. The desirability concept and nonlinear regression approach resulted in the best mechanical property of the FDM-printed part.

The effect of steam sterilization on different 3D printable materials for surgical use in veterinary medicine

BackgroundDifferent 3D-printed materials polyactic acid (PLA), polyamide (PA), polycarbonates (PC), acrylonitrile butadiene styrene (ABS) and GreenTEC Pro®I have been considered for surgical templates, but there is a sparity of data about how these materials are affected by steam sterilization. The aim of the current study was to test if and how these materials change morphologically when high temperature, pressure and humidity are applied during the steam sterilization process. The overall aim is to create patient-specific sawing templates for performing corrective osteotomies. After the designing process, test-specimens with five different materials: PLA, PC, ABS, PA and GreenTEC Pro® were 3D-printed in two filling grades (30 and 100%). The FDM method was used for printing. After 3D-printing, the test-specimens were steam sterilized with a standard program lasting 20 min, at a temperature of 121 °C and a pressure of 2–3 bar. In order to measure the deviation of the printed model, we measured the individual test-specimens before and after steam sterilization using a sliding gauge.ResultsPC, PA and ABS showed great morphological deviations from the template after 3D-printing and steam sterilization (> 1%) respectively. ABS proved unsuitable for steam sterilization. PLA and GreenTEC Pro® demonstrated fewer morphological deviations both before and after sterilization. Therefore, we decided to perform a second test just with PLA and Green-TEC Pro® to find out which material has the highest stability and is probably able to be used for clinical application. The smallest deviations were found with the GreenTEC Pro® solid body. After autoclaving, the specimens showed a deviation from the planned body and remained below the 1% limit.ConclusionSteam sterilization causes morphological deviations in 3D printed objects. GreenTEC Pro® seems to be a suitable material for clinical use, not only for intraoperative use, but also for precise modeling. Microbiological examination, as well as biomechanical tests, should be performed to further assess whether intraoperative use is possible.

Study on 3D printed graphene/carbon fiber multi-scale reinforced PLA composites

In this work, the mechanical and interfacial properties of 3D-printed polyactic acid (PLA) were greatly enhanced through a multi-scale reinforcement technique. In particular, PLA was blended with carbon fiber (CF) and graphene oxide (GO) using a polybutylene succinate (PBS) toughening agent to yield a biodegradable composite with increased strength and tensile modulus. Mechanical enhancement was achieved by adding 0.5 wt% GO and 9 wt% CF, which we prepared through a mechanical stripping method. In comparison to pure PLA, the composite has a 73.33% higher tensile strength, 231.71% higher tensile modulus, and 89.83% higher bending strength. In comparison to CF/PLA, the composite has a 42.48% higher tensile strength, 128.51% higher tensile modulus, and 76.55% higher bending strength.

3D Printed Pressure Sensor Based on Surface Acoustic Wave Resonator

Abstract This paper reports a 3-dimentional (3D) pressure sensor based on surface acoustic wave (SAW) resonators. The SAW resonators were designed and fabricated on 128°Y-X LiNbO3 substrate using the MEMS technology. The pressure sensing structure was 3D-printed using polyactic acid plastic, and two SAW resonators were integrated in the 3D-printed chamber structure for both temperature and pressure sensing. The SAW-based gas pressure sensors demonstrate a sensitivity of 589 ppm/MPa at the pressure range of 100-600 kPa and temperature of 40 °C.

Polymeric membrane based on polyactic acid and babassu oil for wound healing

Chronic skin injuries represent a relevant health problem that affects millions of people worldwide. The development of new therapeutic approaches and dressings can improve the wound healing process. Babassu oil has healing and antimicrobial properties, among others. Thus, this work aimed to develop two biodegradable membranes with Poly (Lactic acid) (PLA) polymer and babassu oil, one using the solvent casting technique, which is an easy technique to produce polymer films, and the other using electrospinning, for the treatment of wound healing. Also, the characterization of membranes was performed using scanning electron microscopy (SEM), X-ray diffraction (XRD), low field Nuclear magnetic resonance (NMR), water uptake ability, water vapor transmission rate (WVTR), cytotoxicity, in vitro wound-healing assay, and the antimicrobial test. The characterization assays showed that the PLA monolithic fibers presented an average diameter of 1015 ± 108 nm, the PLA/babassu monolithic fibers had an average diameter of 959 ± 139 nm. The PLA membranes obtained by solvent casting presented a structure with few pores, and PLA/babassu membranes obtained by solvent casting showed many pores. The randomly oriented nanofibers of PLA obtained by electrospinning have a typical amorphous structure. All membranes presented one well-defined domain in low filed NMR analysis, and it can be interpreted as the membrane`s homogeneity. Finally, the PLA/babassu electrospun membrane is a good option for wound dressings because showed a recommended value of WVTR, maintained a humid environment above the wound, had good cytotoxicity, stimulated the keratinocytes migration, and inhibited Pseudomonas aeruginosa growth.

Material Parameter Identification for Acoustic Simulation of Additively Manufactured Structures.

One possibility in order to manufacture products with very few restrictions in design freedom is additive manufacturing. For advanced acoustic design measures like Acoustic Black Holes (ABH), the layer-wise material deposition allows the continuous alignment of the mechanical impedance by different filling patterns and degrees of filling. In order to explore the full design potential, mechanical models are indispensable. In dependency on process parameters, the resulting homogenized material parameters vary. In previous investigations, especially for ABH structures, a dependency of the material parameters on the structure’s thickness can be observed. In this contribution, beams of different thicknesses are investigated experimentally and numerically in order to identify the material parameters in dependency on the frequency and the thickness. The focused material is polyactic acid (PLA). A parameter fitting is conducted by use of a 3D finite element model and it’s reduced version in a Krylov subspace. The results yield homogenized material parameters for the PLA stack as a function of frequency and thickness. An increasing Young’s modulus with increasing frequency and increasing thickness is observed. This observed effect has considerable influence and has not been considered so far. With the received parameters, more reliable results can be obtained.

The Development of a Novel Device Based on Loss of Guidewire Resistance to Identify Epidural Space in a Porcine Model.

Background The application of additive manufacturing (3D printing) has been recently expanded to various medical fields. The new technique named loss of guide wire resistance (LOGR) was developed via 3D printing for the detection of epidural space using a guide wire instead of air or saline used in the loss of resistance (LOR) technique. Methods The prototype model of epidural space finder consists of a polyactic acid (PLA) or a resin. It was manufactured with 3D printing. Biocompatibility test (eluate and sterility tests) was performed in both products. The advantage of the newly developed device was compared with conventional loss of resistance (LOR) technique in a porcine model. Results Eluate and sterility tests revealed that the PLA was more biocompatible than the resin. The LOGR technique facilitated rapid access to epidural space compared with the LOR technique (41.64 ± 32.18 vs. 92.28 ± 61.46 seconds, N = 14, p=0.0102, paired sample t-test), without any differences in success rate (87.5%). Conclusion We conclude that LOGR technique is comparable to LOR technique to access the epidural space, although the advantage of either technique in terms of complications such as dural puncture or epidural hematoma is unknown. We demonstrated the potential benefit of 3D printer for the development of a new medical device for anesthesia.

Experimental realization of a reconfigurable electroacoustic topological insulator

A substantial challenge in guiding elastic waves is the presence of reflection and scattering at sharp edges, defects, and disorder. Recently, mechanical topological insulators have sought to overcome this challenge by supporting back-scattering resistant wave transmission. In this paper, we propose and experimentally demonstrate a reconfigurable electroacoustic topological insulator exhibiting an analog to the quantum valley Hall effect (QVHE). Using programmable switches, this phononic structure allows for rapid reconfiguration of domain walls and thus the ability to control back-scattering resistant wave propagation along dynamic interfaces for phonons lying in static and finite-frequency regimes. Accordingly, a graphene-like polyactic acid (PLA) layer serves as the host medium, equipped with periodically arranged and bonded piezoelectric (PZT) patches, resulting in two Dirac cones at the K points. The PZT patches are then connected to negative capacitance external circuits to break inversion symmetry and create nontrivial topologically protected bandgaps. As such, topologically protected interface waves are demonstrated numerically and validated experimentally for different predefined trajectories over a broad frequency range.

Compressive Strength Prediction of Quad-Diametral Lattice Structures

Additive manufacturing is rapidly developing technology in all areas of industry. It is reducing the delivering time of each prototype from the manufacturer to the final user. This paper deals with mechanical properties of lattice structures. They are produced by additive technologies from the plastic material. Lattice structures are special space-filling unit cells, which can fill gaps in parts. They have good ratio between overall weight and strength. Nowadays are these structures commonly used, but their mechanical properties are not well described. This makes the design process difficult. Mechanical compressive test and virtual evaluation by the finite element method was performed. It was done for three different Quad-Diametral structures (Quad-Diametral, Quad-Diametral-Line and Quad-Diametral-Cross). Results from both testing approaches (real measurement and finite element method) are deeply described in this paper. It was shown, that the Quad-Diametral-Cross lattice cell has higher mechanical properties comparing to others. Increasing of the stiffness was 121% only with weight higher by 43%. The plastic material Ultimaker PLA (polyactic acid) was used as reference material in this research.

Mechanical, Physical, and Wear Properties of 3D Printed Polyactic Acid Materials

The objective of this paper is to study the mechanical, physical, and wear properties of the 3D printed Polylactic acid (PLA) materials. Tensile Strength, Modulus, and Ductility are investigated as a function of the infill percentage and the printing direction. Shioe D hardness versus infill percentage was investigated. Weight loss versus rolling contact time was investigated to measure the wear properties of the parts. The 3D printed parts have shown a great influence by the infill percentage. Such observation was not found in terms of printing direction. The weight loss due to rolling contact was a function of rolling contact time.

Development of light weight multi-rotor UAV structures through synergistic application of design analysis and fused deposition modelling

Additive manufacturing (AM) technologies are gaining acceptance for fabricating end-use parts in several sectors and this study focuses on developing AM-based approach for gainful development of unmanned aerial vehicles (UAVs). Design-freedom and time-compression are synonymous with AM technologies and to realise the same in the development of UAVs, redesigning of the components is imperative. This paper presents a protocol that synergistically combines design iterations and fused deposition modelling (FDM) for developing light-weight structures for multi-rotor UAVs. Rather than employing expensive industry-grade FDM systems, the present study illustrates a fabrication protocol based on desktop 3D printers and affordable FDM filament material of polyactic acid (PLA). Multiple design configurations are analysed and prototyped leading to considerable weight reduction. The resultant operational benefits that are related to lesser part count, lower assembly effort and higher flight duration as compared to the conventional designs are demonstrated through experimental efforts. A customised process for electrochemical deposition of copper-nickel layers over the PLA parts is developed for enhancement in tensile, flexural and impact performance. Findings from this study lead to new vistas for rapid design iterations through an AM centric fabrication process with consequential impact on ever burgeoning UAV domain.

Application of a Three-dimensional Printed Anatomical Model in Presurgical Planning of Surgical Treatment of Brain Aneurysms

Three dimensional (3D) printed models represent innovative tools in anatomy teaching and surgical planning. The present study aimed at generating 3D skull models incorporating middle cerebral artery (MCA) aneurysms and in assessing their anatomical accuracy and utility as training and preoperative planning tools. Two aneurysm models were generated. Initially, a full skull (model A) and subsequently a half skull (model B) using white polyactic acid (PLA) filament incorporating two arterial networks with hard black PLA filament (in model A) and a softer semitransparent filament (in model B). The models were based on computed tomographic angiography (CTA) of a female patient suffering from bilateral unruptured middle cerebral aneurysms. Model A, a high contrast model, was designed for anatomical illustration purposes. Model B was designed to allow for clipping simulations. The anatomical accuracy of the two models compared to CTA was assessed by measuring their dimensions at the neck, proximal, distal branches and fundus, using an electronic micrometer. The utility of the models for the comprehension of the underlying anatomy, pathology and preoperative planning was evaluated by means of online questionnaires following clipping simulations conducted by neurosurgery residents and specialized neurosurgeons. Of the two 3D printed models generated, model B (clipping model) showed the highest degree of anatomical accuracy. The results of the online survey on the utility of the proposed models indicate that the majority of participants accepted the innovation with positive responses and approve the use of 3D printed aneurysm models for preoperative planning and resident training.

Patient-specific neurosurgical phantom: assessment of visual quality, accuracy, and scaling effects

BackgroundTraining in medical education depends on the availability of standardized materials that can reliably mimic the human anatomy and physiology. One alternative to using cadavers or animal bodies is to employ phantoms or mimicking devices. Styrene-ethylene/butylene-styrene (SEBS) gels are biologically inert and present tunable properties, including mechanical properties that resemble the soft tissue. Therefore, SEBS is an alternative to develop a patient-specific phantom, that provides real visual and morphological experience during simulation-based neurosurgical training.ResultsA 3D model was reconstructed and printed based on patient-specific magnetic resonance images. The fused deposition of polyactic acid (PLA) filament and selective laser sintering of polyamid were used for 3D printing. Silicone and SEBS materials were employed to mimic soft tissues. A neuronavigation protocol was performed on the 3D-printed models scaled to three different sizes, 100%, 50%, and 25% of the original dimensions. A neurosurgery team (17 individuals) evaluated the phantom realism as “very good” and “perfect” in 49% and 31% of the cases, respectively, and rated phantom utility as “very good” and “perfect” in 61% and 32% of the cases, respectively. Models in original size (100%) and scaled to 50% provided a quantitative and realistic visual analysis of the patient’s cortical anatomy without distortion. However, reduction to one quarter of the original size (25%) hindered visualization of surface details and identification of anatomical landmarks.ConclusionsA patient-specific phantom was developed with anatomically and spatially accurate shapes, that can be used as an alternative for surgical planning. Printed models scaled to sizes that avoided quality loss might save time and reduce medical training costs.

P.006 Engineering neurosurgery: role of inter-disciplinary collaboration in development of a remote controlled stereotactic system

Background: Well-crafted engineering solutions have overcome technical challenges faced by surgeons. We present a collaborative effort to develop an innovative solution aimed at saving time and subsequently operating room costs in procedures utilizing a traditional stereotactic system. Methods: We met with our University’s local engineering team to collaborate a solution over a much-appreciated intra-operative technology gap with respect to mechanical adjustment of a stereotactic frame’s co-ordinates. AUTO-CAD software simulated our design, which was materialized with a 3D printer using PLA (polyactic acid). Results: We present a novel stereotactic system where co-ordinates can be digitally entered remotely to localize a point in 3D space. As such, this automated stereotactic frame decreases operative time when compared to manually adjusting a traditional stereotactic system such as the Leksell system. In addition our remote controlled stereotactic system helps minimize human-factor risks and allows one the option to modify stereotactic system co-ordinates from a non-sterile field. Conclusions: Marriage between Engineering and Neurosurgery can improve clinical outcomes for patients suffering from neurological diseases. We provide a grass roots organization’s attempt at overcoming an operative need by designing a remote controlled stereotactic system.

Composite materials for microwave devices using additive manufacturing

Additive manufacturing has been combined with commercially available RF materials to synthesise composite materials whose relative permittivity can be controlled. A design equation for predicting the effective permittivity of these composite materials has also been presented. The relative permittivity of the composite materials was measured by fabricating patch antennas using these materials as the substrate. It has been demonstrated that by using Taconic, polyactic acid (PLA) and air, three materials with different dielectric constants, a large and nearly continuous range of relative permittivity values, from 1.47 to 6.00, can be realised.

FEASIBILITY STUDY OF ULTRASONIC FREQUENCY APPLICATION ON FDM TO IMPROVE PARTS SURFACE FINISH

Fuse Deposition Modeling (FDM) offer several advantages such as less expensive material, lack of expensive lasers and allows complex geometry to be built. However, FDM have limitations such as seam lines appear between layers and excess material residue, leading to surface roughness and poor finish. Ultrasound has been applied in various conventional machining process and shows good machined surface finish. However, from the literature review, it was found there is no investigation made on the application of ultrasound for Additive Manufacturing (AM) especially for FDM. This paper presents an adaptive approach to improve surface finish of FDM sample by applying ultrasonic vibration. The papers discuss the result of the surface finish of test piece printed via a desktop FDM system whereby an ultrasound device that was securely mounted onto the platform during printing process. Frequency that was used in the experiment is 11, 16 and 21 kHz with acrylonitrile butadiene styrene (ABS) material. Optical microscope with the aid of pro VIS software version 2.90 was used to measure the surface roughness of the four samples printed with a vibration in the above specified frequency. It was found that a 21 kHz frequency applied to the FDM process achieved the best surface finish due to less surface defects found and thickness had finer layers being produced. The results from this study could potentially be applied to other AM system such as the selective laser sintering, electron beam machining and stereolithography. The new data on effects of ultrasonic FDM technique and machining parameter for achieving improved surface finish has potential benefit to be used in various industries such as automotive, consumer, medical, sports, etc to produce prototypes or customized end used product or part. The data will benefit in term of product design and development elimination of manual post processing. Further study that could be done is to use different types of material such as polyactic acid (PLA) or composite material.