3D printed flexure hinges for soft monolithic prosthetic fingers

Mechanical compliance is one of the primary properties of structures in nature playing a key role in their efficiency. This study investigates a number of commonly used flexure hinges to determine a flexure hinge morphology, which generates large displacements under a lowest possible force input. The aim of this is to design a soft and monolithic robotic finger. Fused deposition modeling, a low-cost 3D printing technique, was used to fabricate the flexure hinges and the soft monolithic robotic fingers. Experimental and finite element analyses suggest that a nonsymmetric elliptical flexure hinge is the most suitable type for use in the soft monolithic robotic finger. Having estimated the effective elastic modulus, flexion of the soft monolithic robotic fingers was simulated and this showed a good correlation with the actual experimental results. The soft monolithic robotic fingers can be employed to handle objects with unknown shapes and are also potential low-cost candidates for establishing soft and one-piece prosthetic hands with light weight. A three-finger gripper has been constructed using the identified flexure hinge to handle objects with irregular shapes such as agricultural products

A 3D-Printed Omni-Purpose Soft Gripper

Numerous soft grippers have been developed based on smart materials, pneumatic soft actuators, and underactuated compliant structures. In this article, we present a three-dimensional (3-D) printed omni-purpose soft gripper (OPSOG) that can grasp a wide variety of objects with different weights, sizes, shapes, textures, and stiffnesses. The soft gripper has a unique design that incorporates soft fingers and a suction cup that operate either separately or simultaneously to grasp specific objects. A bundle of 3-D-printable linear soft vacuum actuators (LSOVA) that generate a linear stroke upon activation is employed to drive the tendon-driven soft fingers. The support, fingers, suction cup, and actuation unit of the gripper were printed using a low-cost and open-source fused deposition modeling 3-D printer. A single LSOVA has a blocked force of 30.35 N, a rise time of 94 ms, a bandwidth of 2.81 Hz, and a lifetime of 26 120 cycles. The blocked force and stroke of the actuators are accurately predicted using finite element and analytical models. The OPSOG can grasp at least 20 different objects. The gripper has a maximum payload-to-weight ratio of 7.06, a grip force of 31.31 N, and a tip blocked force of 3.72 N

Nanofiltration applications of tough MWNT buckypaper membranes containing biopolymers

© 2017 Elsevier B.V. The ability of biopolymers (bovine serum albumin, lysozyme, chitosan, gellan gum and DNA) to facilitate formation of aqueous dispersions of MWNTs was investigated using a combination of absorption spectrophotometry and optical microscopy. Subsequently, self-supporting carbon nanotube membranes, known as buckypapers (BPs), were prepared by vacuum filtration of the dispersions. Microanalytical data obtained from the BPs confirmed the retention of biopolymers within their structures. Tensile test measurements performed on the BPs showed that incorporation of the biopolymers resulted in significant improvements in mechanical properties, compared to analogous BPs containing MWNTs and the low molecular mass dispersant Triton X-100. For example, MWNT/CHT BPs (CHT=chitosan) exhibited values for tensile strength, ductility, Young's modulus and toughness of 28±2 MPa, 5.3±2.7%, 0.9±0.3 GPa and 1.7±0.3 J g−1, respectively. Each of these values are significantly greater than those obtained for MWNT/Trix BPs, prepared using a low molecular weight dispersant (6±3 MPa, 1.3±0.2%, 0.6±0.3 GPa and 0.10±0.06 J g−1, respectively). This significant improvement in mechanical properties is attributed to the ability of the long biopolymer molecules to act as flexible bridges between the short CNTs. All BPs possessed hydrophilic surfaces, with contact angles ranging from 29±2° to 57±5°. Nitrogen gas porosimetry showed that the BPs have highly porous internal structures, while scanning electron microscopy (SEM) showed their surface morphologies have numerous pore openings. The permeability of the BPs towards water, inorganic salts, and dissolved trace organic contaminants (TrOCs), such as pharmaceuticals, personal care products, and pesticides, was investigated through filtration experiments. Of the twelve TrOCs investigated in this study, nine were rejected by more than 95% by BPs composed of MWNTs and chitosan. The latter BPs also demonstrated good rejection of both NaCl (30–55%) and MgSO4(40–70%)

Design, Modeling and Control of a 3D Printed Monolithic Soft Robotic Finger with Embedded Pneumatic Sensing Chambers

IEEE This paper presents a directly 3D printed soft monolithic robotic finger with embedded soft pneumatic sensing chambers (PSC) as position and touch sensors. The monolithic finger was fabricated using a low-cost and open-source fused deposition modeling (FDM) 3D printer that employs an off-the-shelf soft and flexible commercially available thermoplastic polyurethane (TPU). A single soft hinge with an embedded PSC was optimized using finite element modeling (FEM) and a hyperelastic material model to obtain a linear relationship between the internal change in the volume of its PSC and the corresponding input mechanical modality, to minimize its bending stiffness and to maximize its internal volume. The soft hinges with embedded PSCs have several advantages, such as fast response to very small changes in their internal volume (~0.0026ml/°), linearity, negligible hysteresis, repeatability, reliability, long lifetime and low power consumption. Also, the flexion of the soft robotic finger was predicted using a geometric model for use in real-time control. The real-time position and pressure/force control of the soft robotic finger were achieved using feedback signals from the soft hinges and the touch PSC embedded in the tip of the finger. This study contributes to the development of seamlessly embedding optimized sensing elements in the monolithic topology of a soft robotic system and controlling the robotic system using the feedback data provided by the sensing elements to validate their performance

Bacterial Filtration Using Carbon Nanotube/Antibiotic Buckypaper Membranes

The preparation of free-standing carbon nanotube “buckypaper” (BP) membranes consisting of either single-walled carbon nanotubes (SWNTs) or multi-walled carbon nanotubes (MWNTs), and the antibiotic ciprofloxacin (cipro), is reported. The electrical, mechanical and morphological properties of these membranes have been characterised and are compared to those of the corresponding buckypaper membranes containing the surfactant Triton X-100 (Trix). Analysis of scanning electron microscopic images of the surfaces of SWNT/cipro and SWNT/Trix (Trix  =  Triton X-100) buckypapers revealed that the diameter of their surface pores was significantly smaller than that of the corresponding materials prepared using MWNTs. Similarly, the average internal pore diameter of both SWNT buckypapers was found to be smaller than that of their MWNT counterparts, after analysis of binding isotherms derived from nitrogen adsorption/desorption measurements performed on the materials. All four buckypaper membranes examined were found to be >99% effective for removing Escherichia coli (E. coli) from aqueous suspensions. However, buckypapers containing ciprofloxacin outperformed their counterparts containing the surfactant. Both MWNT buckypapers were more effective at preventing passage of E. coli than their analogues containing SWNTs, while fluorescence microscopic examination of stained membrane surfaces demonstrated that buckypapers composed of SWNTs had greater bactericidal properties

3D Printing of Transparent and Conductive Heterogeneous Hydrogel-Elastomer Systems

Hydrogel-based ionic devices represent an alternative approach to stretchable electronics through use of soft ionic conductors that are both highly stretchable and transparent. However, these devices require the integration of dissimilar materials, dielectric elastomers and hydrogels, into a single system; a process thus far achieved primarily via the combination of several different manufacturing techniques. We have developed a 3D extrusion printing technique capable of fabricating an entire ionic circuit that integrates a LiCl-doped poly(acrylamide) (PAAm) hydrogel with a poly(dimethylsiloxane) (PDMS) dielectric elastomer. By incorporating hygroscopic salts such as LiCl into the hydrogel, we are able to prepare an ionically conductive hydrogel with excellent water-retaining properties. For printing reliability, we have optimized the rheological properties of a high ionic-strength hydrogel precursor and the interfacial energy between PDMS and hydrogel. Printed ionic devices that consist of PAAm and PDMS exhibit outstanding mechanical and electrical stability when tested with up to 1000 cycles of uniaxial tension. Moreover, we successfully demonstrate functionality in terms of signal transmission and as a soft sensor by fabricating and characterizing an ionic cable and several strain gauges.Engineering and Applied Science

Time-restricted feeding attenuates hypercholesterolaemia and atherosclerosis development during circadian disturbance in APOE∗3-Leiden.CETP mice

Circadian disturbance (CD) is the consequence of a mismatch between endogenous circadian rhythms, behaviour, and/or environmental cycles, and frequently occurs during shift work. Shift work has been associated with elevated risk for atherosclerotic cardiovascular disease (asCVD) in humans, but evidence for the effectiveness of prevention strategies is lacking.\nHere, we applied time-restricted feeding (TRF) as a strategy to counteract atherosclerosis development during CD in female APOE∗3-Leiden.CETP mice, a well-established model for humanized lipoprotein metabolism. Control groups were subjected to a fixed 12:12 h light-dark cycle, while CD groups were subjected to 6-h phase advancement every 3 days. Groups had either ad libitum (AL) access to food or were subjected to TRF with restricted food access to the dark phase.\nTRF did not prevent the increase in the relative abundance of circulating inflammatory monocytes and elevation of (postprandial) plasma triglycerides during CD. Nonetheless, TRF reduced atherosclerotic lesion size and prevented an elevation in macrophage content of atherosclerotic lesions during CD, while it increased the relative abundance of anti-inflammatory monocytes, prevented activation of T cells, and lowered plasma total cholesterol levels and markers of hepatic cholesterol synthesis. These effects were independent of total food intake.\nWe propose that time restricted eating could be a promising strategy for the primary prevention of asCVD risk in shift workers, which warrants future study in humans.\nThis work was funded by the Novo Nordisk Foundation, the Netherlands Ministry of Social Affairs and Employment, Amsterdam Cardiovascular Sciences, and the Dutch Heart Foundation.Biopharmaceutic

Synthesis, properties and water permeability of SWNT buckypapers

The ability of macrocyclic ligands to facilitate formation of dispersions of single-walled carbon nanotubes (SWNTs) was investigated using a combination of absorption spectrophotometry and optical microscopy. Vacuum filtration of aqueous dispersions containing SWNTs and various macrocyclic ligands (derivatised porphyrin, phthalocyanine, cyclodextrin and calixarene) afforded self-supporting membranes known as buckypapers. Microanalytical data and energy dispersive X-ray spectra were obtained for these buckypapers and provided evidence for retention of the macrocyclic ligands within the structure of the membranes. The electrical conductivities of the membranes varied between 30 ± 20 and 220 ± 60 S cm−1, while contact angle analysis revealed they all possessed hydrophilic surfaces. The mechanical properties of buckypapers prepared using macrocyclic ligands as dispersants were shown to be comparable to that of a benchmark material prepared using the surfactant Triton X-100 (Trix). Incorporation of the macrocyclic ligands into SWNT buckypapers was found to increase their permeability up to ten-fold compared to buckypapers prepared using Trix. No correlation was observed between the water permeability of the membranes and the average size of either their surface or internal pores. However, the water permeability of the membranes was found to be inversely dependent on their surface area

PET Imaging of Soluble Yttrium-86-Labeled Carbon Nanotubes in Mice

The potential medical applications of nanomaterials are shaping the landscape of the nanobiotechnology field and driving it forward. A key factor in determining the suitability of these nanomaterials must be how they interface with biological systems. Single walled carbon nanotubes (CNT) are being investigated as platforms for the delivery of biological, radiological, and chemical payloads to target tissues. CNT are mechanically robust graphene cylinders comprised of sp(2)-bonded carbon atoms and possessing highly regular structures with defined periodicity. CNT exhibit unique mechanochemical properties that can be exploited for the development of novel drug delivery platforms. In order to evaluate the potential usefulness of this CNT scaffold, we undertook an imaging study to determine the tissue biodistribution and pharmacokinetics of prototypical DOTA-functionalized CNT labeled with yttrium-86 and indium-111 ((86)Y-CNT and (111)In-CNT, respectively) in a mouse model.The (86)Y-CNT construct was synthesized from amine-functionalized, water-soluble CNT by covalently attaching multiple copies of DOTA chelates and then radiolabeling with the positron-emitting metal-ion, yttrium-86. A gamma-emitting (111)In-CNT construct was similarly prepared and purified. The constructs were characterized spectroscopically, microscopically, and chromatographically. The whole-body distribution and clearance of yttrium-86 was characterized at 3 and 24 hours post-injection using positron emission tomography (PET). The yttrium-86 cleared the blood within 3 hours and distributed predominantly to the kidneys, liver, spleen and bone. Although the activity that accumulated in the kidney cleared with time, the whole-body clearance was slow. Differential uptake in these target tissues was observed following intravenous or intraperitoneal injection.The whole-body PET images indicated that the major sites of accumulation of activity resulting from the administration of (86)Y-CNT were the kidney, liver, spleen, and to a much less extent the bone. Blood clearance was rapid and could be beneficial in the use of short-lived radionuclides in diagnostic applications