Influence of infill patterns generated by CAD and FDM 3D printer on surface roughness and tensile strength properties

Fused deposition modeling (FDM) is a capable technology based on a wide range of parameters. The goal of this study is to make a comparison between infill pattern and infill density generated by computer-aided design (CAD) and FDM. Grid, triangle, zigzag, and concentric patterns with various densities following the same structure of the FDM machine were designed by CAD software (CATIA V5®). Polylactic acid (PLA) material was assigned for both procedures. Surface roughness (SR) and tensile strength analysis were conducted to examine their effects on dog-bone samples. Also, a finite element analysis (FEA) was done on CAD specimens to find out the differences between printing and simulation processes. Results illustrated that CAD specimens had a better surface texture compared to the FDM machine while tensile tests showed patterns generated by FDM were stronger in terms of strength and stiffness. In this study, samples with concentric patterns had the lowest average SR (Ra) while zigzag was the worst with the value of 6.27 µm. Also, the highest strength was obtained for concentric and grid samples in both CAD and FDM procedures. These techniques can be useful in producing highly complex sandwich structures, bone scaffolds, and various combined patterns to achieve an optimal condition

Soft pneumatic actuators with controllable stiffness by bio‐inspired lattice chambers and fused deposition modeling 3D printing

This article shows how changing 3D printing parameters and using bio-inspired lattice chambers can engineer soft pneumatic actuators (SPAs) with different behaviors in terms of controlling tip deflection and tip force using the same input air pressure. Fused deposition modeling (FDM) is employed to 3D print soft pneumatic actuators using varioShore thermoplastic polyurethane (TPU) materials with a foaming agent. The effects of material flow and nozzle temperature parameters on the material properties and stiffness are investigated. Auxetic, columns, face-centered cubic, honeycomb, isotruss, oct vertex centroid, and square honeycomb lattices are designed to study actuators’ behaviors under the same input pressure. Finite-element simulations based on the nonlinear hyper-elastic constitutive model are carried out to precisely predict the behavior, deformation, and tip force of the actuators. A closed-loop pneumatic system and sensors are developed to control the actuators. Results show that lattice designs can control the bending angle and generated force of actuators. Also, the lattices increase the ultimate strength by controlling the contact area inside the chambers. They demonstrate variable stiffness behaviors and deflections under the same pressure between 100 and 500 kPa. The proposed actuators could be instrumental in designing wearable hand rehabilitative devices that assist customized finger and wrist flexion-extension

3D‐printed soft and hard meta‐structures with supreme energy absorption and dissipation capacities in cyclic loading conditions

The main objective of this article is to introduce novel 3D bio-inspired auxetic meta-structures printed with soft/hard polymers for energy absorption/dissipation applications under single and cyclic loading–unloading. Meta-structures are developed based on understanding the hyper-elastic feature of thermoplastic polyurethane (TPU) polymers, elastoplastic behavior of polyamide 12 (PA 12), and snowflake inspired design, derived from theory and experiments. The 3D meta-structures are fabricated by multi-jet fusion 3D printing technology. The feasibility and mechanical performance of different meta-structures are assessed experimentally and numerically. Computational finite element models (FEMs) for the meta-structures are developed and verified by the experiments. Mechanical compression tests on TPU auxetics show unique features like large recoverable deformations, stress softening, mechanical hysteresis characterized by non-coincident compressive loading–unloading curve, Mullins effect, cyclic stress softening, and high energy absorption/dissipation capacity. Mechanical testing on PA 12 meta-structures also reveals their elastoplastic behavior with residual strains and high energy absorption/dissipation performance. It is shown that the developed FEMs can replicate the main features observed in the experiments with a high accuracy. The material-structural model, conceptual design, and results are expected to be instrumental in 3D printing tunable soft and hard meta-devices with high energy absorption/dissipation features for applications like lightweight drones and unmanned aerial vehicles (UAVs)

Evaluation of four different DNA extraction methods from dwarf honeybee Apis florea (Hymenoptera: Apidae) for genetic experiments

Background and Objectives DNA extraction is the first step of genetic experiments. In this regard, quality and quantity of extracted DNA plays an important role in molecular studies. This experiment was conducted in order to achieve a novel method that helps us to extract DNA from Apis florea F (one of two important Iranian honeybee). This species is regarded as an important honeybee due to its world-wide distribution and direct role in pollination of field crops, orchards and forests. Materials and Methods Samples were collected randomly from the hives of dwarf honeybee in Khuzestan province. In the current research, DNA was extracted from the thorax tissues of worker bees. Totally, four DNA extraction methods were evaluated including the optimal salting out, phenol-chloroform, CTAB and CTAB+SDS. To evaluate the quality of extracted DNA, spectrophotometry, electrophoresis and agarose gel methods were applied to compare quantity and quality of DNA extraction. Results Quantity and quality of extracted DNA was evaluated by spectrophotometry based on the absorption ratio 260/280 and electrophoresis on agarose gel. Based on the absorption ratio, for the methods of salting out, phenol-chloroform, CTAB and CTAB + SDS were 1.15 ± 0.01, 1.37 ± 0.01, 1.72 ± 0.02 and 1.82 ± 0.01, respectively. Duncan multiple range test revealed that CTAB+SDS was significantly different from other methods for evaluation of DNA extraction. Discussion Based on the results, the quality of DNA visible bands on the agarose gel can be considered as the option to evaluate the quality of DNA. On the other hand, twice washing in the CTAB + SDS method reduced protein contamination significantly. Furthermore, it could be mentioned that all the DNA extraction methods used in this study seems to be suitable in polymerase chain reaction test, but CTAB+SDS resulted in higher DNA quality and quantity. We referred to this thorax tissue as “thoracic muscle mass”, which could be as candidate tissue to obtain larger quantities of DNA

Silicon-based soft parallel robots 4D printing and multiphysics analysis

Four-dimensional (4D) printing has set the stage for a new generation of soft robotics. The applications of rigid planar parallel robotic manipulators are also significant because of their various desirable characteristics, such as lower inertia, higher payload, and high accuracy. However, rigid planar parallel robots are heavy and require different actuators and components. This study introduces a novel technique to produce a light three degrees of freedom (DOF) soft parallel manipulator at a low cost, which can be stimulated easily. This technique allows researchers to customize the actuator's design based on the requirement. The robot is made by 3D printing based on fused deposition modelling (FDM) and a direct ink writing (DIW) process. The design, development, and additive manufacturing (AM) of a soft parallel robot electrothermally driven by a linear silicon-based actuator and polylactic acid (PLA) parts are presented. Silicon-based soft actuators replace the rigid conventional linear actuators in this study to drive the planar parallel manipulator. The actuation of actuators is conducted using simple heating compared to the conventional rigid actuator. Various heating approaches and configurations are compared and analysed to find the most suitable one for the effective linear stroke of the soft actuator. The finite element model (FEM) is used to analyse the performance of the electrothermally silicon-ethanol soft actuators in ABAQUS. The kinematics of the planar parallel robotic manipulator are simulated in MATLAB to achieve its workspace. The final soft parallel robot mechanism and the active and passive links are fabricated and tested experimentally

Simultaneous FDM 4D printing and magnetizing of iron-filled polylactic acid polymers

4D printing magnetic structures with excellent strength activated with a low level of the magnetic field is always desired but challenging. This work studies the influence of simultaneous magnetization on the magneto-mechanical performance of 4D-printed active polymers. The main aim is to magnetise magnetic iron polylactic acid (PLA) material during 4D printing via fused deposition modelling (FDM) process. During the printing process, the magnetization of the samples is performed in various magnetic field states. Specimens are printed in three states with two magnets around the printing area, magnets under the printing area, and without magnets, at three angles of 0, 45, and 90° to the applied magnetic field. Vibrating sample magnetometer (VSM), mechanical tests, and scanning electron microscope (SEM) are used to investigate the effects of the applied magnetic field on the magnetization with different printing conditions, mechanical properties of different printing angles, and the microstructure of printed samples. Results show that printed samples on the edge of the magnet are saturated in a higher specific magnetization compared to the printed samples with magnets around and without a magnetic field. The specific magnetization in the magnetic field in the direction of the sample deposition increases by 63.46% by applying a magnetic field. The strength increases 21.4% when a magnetic field is present, and the sample is printed at 0° angle along the tension direction. The printed sample has better mechanical properties when two magnets are used around the printing region rather than one under it, which is independent of the impact of the printing angle. Finally, the optimal printing mode for obtaining the appropriate magnetic and mechanical characteristics is 3D printing with magnets under the printing bed at 0° angle along the tension direction