Polyamide 11-Carbon Nanotubes Nanocomposites: Preliminary Investigation

The objective of this research is to develop an improved polyamide 11 (PA11) polymer with enhanced flame retardancy, thermal, and mechanical properties for selective laser sintering (SLS) rapid manufacturing. In the present study, a nanophase was introduced into polyamide 11 via twin screw extrusion. Arkema Rilsan® polyamide 11 molding polymer pellets were used with 1, 3, 5, and 7 wt% loadings of Arkema’s GraphistrengthTM multi-wall carbon nanotubes (MWNTs) to create a family of PA11-MWNT nanocomposites. Transmission electron microscopy and scanning electron microscopy were used to determine the degree and uniformity of dispersion. Injection molded test specimens were fabricated for physical, thermal, mechanical properties, and flammability measurements. Thermal stability of these polyamide 11-MWNT nanocomposites was examined by TGA. Mechanical properties such as ultimate tensile strength, rupture tensile strength, and elongation at rupture were measured. Flammability properties were also obtained using the UL 94 test method. All these different methods and subsequent polymer characteristics are discussed in this paper.Mechanical Engineerin

Quick-cast: A method for fast and precise scalable production of fluid-driven elastomeric soft actuators

Fluid-driven elastomeric actuators (FEAs) are among the most popular actuators in the emerging field of soft robotics. Intrinsically compliant, with continuum of motion, large strokes, little friction, and high power-to-weight ratio, they are very similar to biological muscles, and have enabled new applications in automation, architecture, medicine, and human-robot interaction. To foster future applications of FEAs, in this paper we present a new manufacturing method for fast and precise scalable production of complex FEAs of high quality (leak-free, single-body form, with <0.2 mm precision). The method is based on 3d moulding and supports elastomers with a wide range of viscosity, pot life, and Young's modulus. We developed this process for two different settings: one in laboratory conditions for fast prototyping with 3d printed moulds and using multi-component liquid elastomers, and the other process in an industrial setting with 3d moulds micromachined in metal and applying compression moulding. We demonstrate these methods in fabrication of up to several tens of two-axis, three-chambered soft actuators, with two types of chamber walls: cylindrical and corrugated. The actuators are then applied as motion drivers in kinetic photovoltaic building envelopes

FTIR spectroscopic and thermogravimetric characterization of ground tyre rubber devulcanized by microwave treatment

In this work the phenomena involved with the microwave devulcanization of ground tyre rubber (GTR) were investigated. During studies three types of GTR characterized by different content of organic compounds (elastomers, plasticizers, etc..), carbon black and ash have been analyzed. The chemical structure of GTR before and after microwave devulcanization process was studied by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Furthermore, efficiency of microwave devulcanization conducted at different time was evaluated based on the crosslinking density and sol content values. FTIR spectroscopy results shown that devulcanization of GTR causes a decrease in carbon black with generation of CO2 due to its thermo oxidation, a decrease in structural groups of elastomeric components (mainly methylene and methine) and a breaking of C-S groups and S-S bridges. The presented results indicate the strong correlation between content of SiO2 in GTR and its degree of devulcanization. It was observed that GTR with a high content of SiO2 are easier devulcanized than samples with low content of SiO2, which suggest the presence of silica fillers improve microwave devulcanization efficiencyPostprint (author's final draft

Characterisation and replication of metallic micro-fluidic devices using three different powders processed by hot embossing

International audienceThis study presents the results of micro-replication of different powder feedstocks samples. The feedstocks of metal powder and plastic binder with various solid loading in the range from 40% to 75% were prepared. The different feedstock comprises 316 L stainless steel, Fe\Ni 8%, orWC-Co and amulti-component binder system. Suitable polymers/powder formulations for the hot embossing were chosen and characterised by thermogravimetric analyses (TGA), mixer measurements and capillary rheology testing in order to check and quantify the viscosity and homogeneity of all the developed feedstocks. The photoresist (SU-8) was used as a structural material that was deposited onto the Si wafer to obtain the micro-fluidic systems with low roughness. Then the elastomeric mouldwas obtained using casting with one face that contains all the details of the originalmaster, very well defined and smooth sidewalls. The objective of the paper is to develop metallic micro-structured die mould cavities with higher quality using hot embossing process with various different powder loaded polymers. However, a rapid prototyping process was adapted for fast and cost-efficient manufacturing. This study compares the capacities of three different metallic powders to emboss of the metallic replications by hot embossing, the dimensional stability, the mechanical strength and particularly hardness of sintered components. The results show that the feedstock can be used for the manufacturing of the micro-fluidic die mould cavities with a low roughness, proper dimensions and good shape retention

A Novel Projection Based Electro-Stereolithography (PES) Process for Composite Printing

Most current additive manufacturing processes can only process one material in one build. Few of them are able to fabricate multiple materials and composites, with limited choices of materials. In this research, we propose a novel Projection based Electro-Stereolithography (PES) process, which is able to fabricate composites with high resolution and fast speed, and a big range of material choices. The proposed novel additive manufacturing process integrates projection-based stereolithography and electrophotography approaches by using a photoconductive film and digital micro-mirror device (DMD). In PES, a photoconductive film is used to collect charged particles in the regions illuminated by light. More specifically, a laser beam is scanning on the film to create a latent image on the film and then a layer of charged particles is attracted to the illuminated area. A liquid bridge system and a stamping system have been developed to transfer particles from the film to liquid resin precisely. Furthermore, a digital mask is used to pattern the light irradiation of the DMD chip to selectively cure the photopolymer liquid resin and particles of that layer. By transferring particles with designed patterns to the resin in a projection based stereolithography system, we will be able to fabricate composites with various materials at microscopic resolutions very quickly. Challenges in this novel manufacturing process, including transferring of particles and curing control, have been discussed and addressed. The corresponding key parameters of the particles collecting, dropping and curing in the PES system have been identified. A proof-of-concept PES testbed has been developed and a couple of tests have been performed to validate the feasibility of the proposed additive manufacturing approach.Mechanical Engineerin

Experimental investigation of the mechanical stiffness of periodic framework-patterned elastomers

Recent advances in the cataloguing of three-dimensional nets mean a systematic search for framework structures with specific properties is now feasible. Theoretical arguments about the elastic deformation of frameworks suggest characteristics of mechanically isotropic networks. We explore these concepts on both isotropic and anisotropic networks by manufacturing porous elastomers with three different periodic net geometries. The blocks of patterned elastomers are subjected to a range of mechanical tests to determine the dependence of elastic moduli on geometric and topological parameters. We report results from axial compression experiments, three-dimensional X-ray computed tomography imaging and image-based finite-element simulations of elastic properties of framework-patterned elastomers

Development of a Fabrication Technique for Soft Planar Inflatable Composites

Soft robotics is a rapidly growing field in robotics that combines aspects of biologically inspired characteristics to unorthodox methods capable of conforming and/or adapting to unknown tasks or environments that would otherwise be improbable or complex with conventional robotic technologies. The field of soft robotics has grown rapidly over the past decade with increasing popularity and relevance to real-world applications. However, the means of fabricating these soft, compliant and intricate robots still poses a fundamental challenge, due to the liberal use of soft materials that are difficult to manipulate in their original state such as elastomers and fabric. These material properties rely on informal design approaches and bespoke fabrication methods to build soft systems. As such, there are a limited variety of fabrication techniques used to develop soft robots which hinders the scalability of robots and the time to manufacture, thus limiting their development. This research focuses towards developing a novel fabrication method for constructing soft planar inflatable composites. The fundamental method is based on a sub-set of additive manufacturing known as composite layering. The approach is designed from a planar manner and takes layers of elastomeric materials, embedded strain-limiting and mask layers. These components are then built up through a layer-by-layer fabrication method with the use of a bespoke film applicator set-up. This enables the fabrication of millimetre-scale soft inflatable composites with complex integrated masks and/or strain-limiting layers. These inflatable composites can then be cut into a desired shape via laser cutting or ablation. A design approach was also developed to expand the functionality of these inflatable composites through modelling and simulation via finite element analysis. Proof of concept prototypes were designed and fabricated to enable pneumatic driven actuation in the form of bending soft actuators, adjustable stiffness sensor, and planar shape change. This technique highlights the feasibility of the fabrication method and the value of its use in creating multi-material composite soft actuators which are thin, compact, flexible, and stretchable and can be applicable towards real-world application

Fatigue Characterization of 3D Printed Elastomer Material

The Objet PolyJet 3D Printing process provides the ability to print graded materials featuring both stiff and elastomeric polymers. This capability allows for a variety of new design possibilities for additive manufacturing such as living hinges, shock absorbing casings, and integrated gaskets. Such design features typically rely upon the ability of traditional elastomers to experience large and repeated strains without permanent deformation or damage. However, voids and other flaws inherent to many Additive Manufacturing (AM) processes can have a significant negative impact on the fatigue life of elastomeric AM materials. In this paper, the authors seek to fill a gap in the literature by characterizing the fatigue life of a direct 3D printed elastomer, and the multi-material interface. Based on the results, the authors offer advice for improving fatigue life of printed elastomeric components.Mechanical Engineerin

Rapid, multiplexed microfluidic phage display

The development of a method for high-throughput, automated proteomic screening could impact areas ranging from fundamental molecular interactions to the discovery of novel disease markers and therapeutic targets. Surface display techniques allow for efficient handling of large molecular libraries in small volumes. In particular, phage display has emerged as a powerful technology for selecting peptides and proteins with enhanced, target-specific binding affinities. Yet, the process becomes cumbersome and time-consuming when multiple targets are involved.Here we demonstrate for the first time a microfluidic chip capable of identifying high affinity phage displayed peptides for multiple targets in just a single round and without the need for bacterial infection. The chip is shown to be able to yield well-established control consensus sequences while simultaneously identifying new sequences for clinically important targets. Indeed, the confined parameters of the device allow not only for highly controlled assay conditions but also introduce a significant time-reduction to the phage display process. We anticipate that this easily-fabricated, disposable device has the potential to impact areas ranging from fundamental studies of protein, peptide, and molecular interactions, to applications such as fully automated proteomic screening