Soft Filament Research Articles

Surface roughness difference of bis-acryl provisional crown material under different toothbrush filament and toothpaste abrasive degree

Introduction: Brushing of provisional crown material using a toothbrush and abrasive toothpaste induced surface roughness. This study aim to determine differences in surface roughness on bis-acryl provisional crown material brushed under soft and medium filament toothbrushes with a combination of high and low abrasive toothpaste. Methods: This laboratory experimental study used 40 samples in 4 groups consisted of 10 samples for each group. Samples brushing method was carried out using a Modified V8-Brushing Machine tool for 2000 cycles at a speed of 120 cycles/minutes and a 0.2 N pressure. Results: Surface roughness measurements were measured using a profilometer. Kruskal-Wallis Statistical analysis test was used to determine significant differences between test groups. This study indicate that there is a difference in surface roughness on bis-acryl provisional crown material brushed with soft and medium filament toothbrushes with a combination of high and low abrasive toothpaste p = 0.01 (p < 0.05). Conclusion: Brushing with a medium filament toothbrush resulted in higher roughness value than brushing with a soft filament toothbrush and the group brushed with high abrasive toothpaste showed higher roughness values than brushing with low abrasive toothpaste.

Thermally-modulated shape transition at the interface of soft gel filament and hydrophobic substrate

A liquid filament may pinch off into different shapes on interacting with a soft surface, as modulated by the interplay of inertial, capillary, and viscous forces. While similar shape transitions may intuitively be realized for more complex materials such as soft gel filaments as well, their intricate controllability towards deriving precise and stable morphological features remains challenging, as attributed to the complexities stemming from the underlying interfacial interactions over the relevant length and time scales during the sol–gel transition process. Circumventing these deficits in the reported literature, here we report a new means of precisely-controlled fabrication of gel microbeads via exploiting thermally-modulated instabilities of a soft filament atop a hydrophobic substrate. Our experiments reveal that abrupt morphological transitions of the gel material set in at a threshold temperature, resulting in spontaneous capillary thinning and filament breakup. We show that this phenomenon may be precisely modulated by an alteration in the hydration state of the gel material that may be preferentially dictated by its intrinsic glycerol content. Our results demonstrate that the consequent morphological transitions give rise to topologically-selective microbeads as an exclusive signature of the interfacial interactions of the gel material with the deformable hydrophobic interface underneath. Thus, intricate control may be imposed on the spatio-temporal evolution of the deforming gel, facilitating the inception of highly ordered structures of specific shapes and dimensionalities on demand. This is likely to advance the strategies of long shelf-life analytical biomaterial encapsulations via realizing one-step physical immobilization of bio-analytes on the bead surfaces as a new route to controlled materials processing, without demanding any resourced microfabrication facility or delicate consumable materials.

A Stretchable Filament Sensor with Tunable Sensitivity for Wearable Robotics and Healthcare Applications

AbstractTaking a leaf out of evolutionary biology, soft robots have begun to utilize compliant materials and structures for improved interactions with humans and complex environments. However, these advances have not been followed closely by sensing mechanisms. Biology has had a head start on the development of advanced sensing systems. The human body and its skeletal muscles can tune their morphologies to interact with the surrounding environment. Inspired by such biological systems, this paper introduces a novel hydraulic soft filament sensor (SFS) with tunable sensitivity. The SFS is a type of hydraulic pressure‐based tubular strain sensor, which has a sensing core made of a soft and stretchable micro‐sized filament filled with incompressible fluid where its inner hydraulic pressure is changed with strain. The SFS can be customized to form a wide range of configurations such as a long fiber or a skin‐like structure. To demonstrate the SFS capability, different configurations for the SFS are fabricated and experimentally validated. The scalable and tunable nature of the SFS makes it suitable for a wide range of wearable and medical applications.

Desktop printing of 3D thermoplastic polyurethane parts with enhanced mechanical performance using filaments with varying stiffness

3D printing polymers via fused filament fabrication (FFF) exhibits significant advantages such as low cost and high efficiency, thus FFF has become one of the most popular production methods in the 3D printing field. For a printing using a soft filament feedstock, it is important to understand how to optimize its fabrication process when attempting to improve the packing morphology of deposited melt strand and thus enhance the mechanical performance. This work intends to be a step forward obtaining a strategy for high-quality FFF printing without compromising printing efficiency for those filaments with low stiffness as well as low feeding stress. Using a commercial desktop printer, a facile method to reduce the porosity of FFF-printed thermoplastic polyurethane (TPU) parts was proposed by controlling printing parameters using specific TPU filaments with varying hardness. Tensile strength and tear resistance of the printed parts were measured to assess the optimization printing (OP) strategy. Owing to the significant reduction of porosity, less thermal degradation and higher molecular orientation in FFF, the tensile strength and tear resistance of the OP-printed parts were approximately 95% and 126.8% of those of parts fabricated via injection molding, respectively. Compared with the standard printing (SP) method, OP strategy was found to be effective in improving mechanical performance. The mechanism was then analyzed in terms of nozzle moving trajectory and filament loading ratio, with particular emphasis on feedstock in the continuity and stability of melt strand deposition. In addition, the correlation between residual porosity and mechanical performance of FFF-printed parts was established, providing direction for overcoming the practical limitations of FFF printing, thus paving a way to print high-quality elastomeric materials.

Development of Multi-Material 3D Printer

We present development of multi-material Fused deposition modeling (FDM) 3D printer. Most of the FDM type of 3d printers are able to print plastics such as ABS, PLA and Nylon in a single run. In order to overcome this problem, we have developed an affordable multi-material 3D printer that can print an object with a different kind of soft and hard material in a single run. The combination of printing soft and hard materials in a single run will open the doors to various applications such as soft robotics, actuators and sensors. One of the main printing materials for this printer is the conductive based soft filament made by our laboratory “Soft & Wet Matter Engineering Laboratory”, along with other different soft filament and hard plastic filament to create a fully functional, multi-material printer to print objects in a single printing run with greater diversity and lower cost than any other single material printer. We have developed a single screw-based extruder 3D printer extruder type 3D printer that can print both soft and hard materials. Instead of using a filament to 3D print objects, we have used pellets of different materials, including carbon-based conductive composites. Such type of single screw base extruder 3D printer will be a new addition to the additive manufacturing process.

Development of Multi-Material 3D Printer

The aim of developing a multi-material 3D printer is to print an object with a different kind of soft and hard material in a single run. It is expected that the combination of printing soft and hard material will be a new kind of 3D printer. The main printing material for this printer is the conductive based soft filament made by our laboratory “Soft & Wet Matter Engineering Laboratory”, along with other different soft filament and hard plastic filament to create a fully functional, multi-material printer to print objects in a single printing run with greater diversity and lower cost than any other single material printer. The biggest challenge for making this printer is to develop a soft material’s extruder because in 3D printer most of the materials are used is hard filament. So, to overcome this we are developing a special type of screw-based Extruder, where a huge range of polymer material can be processed in an application of 3D printer objects. This type of extruder is not so common in 3D printing field. Instead of the filament, we will use the conductive material as pellet or powder for this screw-based extruder. It is assumed that this type of screw-based extruder can solve the problem of combination of printing soft and hard material in a single run. Such type of screw base extruder will be a new era of the 3D printer and it could be a good STEM tool in Sensor and Robotics. Moreover, it is expected that it will be a new addition to the additive manufacturing process.

Rotational dynamics of a soft filament: Wrapping transition and propulsive forces

We experimentally analyze the shape of a long elastic filament rotating in a viscous liquid. We identify a continuous but sharp transition from a straight to an helical shape, resulting from the competition between viscous stresses and elastic forces. This induced helicity generates a propulsive force along the axis of rotation. In addition, we show that the shape transition is associated with an unstable branch in the force-torque relation, confirming the numerical predictions of Manghi et al. [Phys. Rev. Lett. 96, 068101 (2006)]. A linearized model of the fluid-structure interaction is proposed to account for all the features of the nonlinear filament dynamics.

AC 114: A Cluster with a Soft X‐Ray Tail

We present Chandra observations of the galaxy cluster AC 114. The cluster shows a strongly irregular morphology, with signs of multiple merging activity. We report the discovery of a soft X-ray filament originating close to the core of the cluster, curving to the southeast for approximately 15. We confirm that X-ray emission is associated with two of three mass concentrations identified in previous gravitational lensing studies of this object. These two mass concentrations are located at opposite ends of the soft filament, and we interpret this as evidence for interaction between them. The northern part of the cluster reveals signs of further dynamical activity. Two sharp discontinuities are detected in both the surface brightness and temperature profiles, evincing another more recent merger event that took place in or close to the cluster core. A preliminary combined mass and lensing analysis shows, in spite of the merger activity, remarkably good agreement between lensing and X-ray masses computed with the assumption of hydrostatic equilibrium.