Soft Polymeric Materials Research Articles

Static and Dynamic Tensile Mechanical Behavior of Polyvinyl Chloride Elastomers with Different Shore Hardness

An experiment on the static and dynamic tensile mechanical properties of polyvinyl chloride (PVC) elastomers is conducted using an Instron-5943 universal testing machine and an improved Split Hopkinson Tensile Bar to study the dynamic tensile mechanical properties of PVC elastomer materials. The stress-strain curves of PVC materials with three types of Shore hardness (57A, 52A, and 47A) under the strain rates of 0.1 s−1 and 400 ∼ 1800 s−1 are obtained. Results show that the mechanical behavior of PVC elastomer materials with different Shore hardness has remarkable linear elastic characteristics under the action of quasistatic tensile load. It has substantial sensitivity to strain rate and viscoelastic mechanical characteristics under the action of dynamic tensile load. The Zhu–Wang–Tang nonlinear viscoelastic constitutive model is used to characterize the viscoelastic mechanical characteristics with small error. This paper can provide theoretical model and method support for the design, development, production, and reliability analysis of PVC elastomers and other soft polymer materials.

How accurately do mechanophores report on bond scission in soft polymer materials?

AbstractMechanophores are molecules that are incorporated into a host material and react to the local mechanical condition—the state of stress or strain—of that host material. Among their many purposes is that of a reporter: Mechanophores whose optical activity changes in response to mechanical cues can reveal bulk material processes that are ordinarily hidden, such as fatigue and fracture. Moreover, they may do so well before a material is fully fractured. To extract quantitative information from the optical signals from embedded mechanophores it is important that the mechanophores, which are generally a minority component of the material, report proportionally and unambiguously on the mechanical condition of the bulk. This is particularly important for early reporting of damage and wear, for which the optical signal from the mechanophore should accurately reflect bulk bond scission. In this article, we develop and analyze a general theory for the quality of optical mechanoreporting by mechanophores in soft materials, based on the Bell‐Evans theory of bond breaking. We find, that at the typical low fractions in which mechanophores are incorporated the overall change in strength is limited, but that the proportionality of the reporting can be off by significant amounts, particularly at short times after loading but, for non‐scissile bonds, at long times as well.

Coupled liquid crystalline oscillators in Huygens' synchrony.

In the flourishing field of soft robotics, strategies to embody communication and collective motion are scarce. Here we report the synchronized oscillations of thin plastic actuators by an approach reminiscent of the synchronized motion of pendula and metronomes. Two liquid crystalline network oscillators fueled by light influence the movement of one another and display synchronized oscillations in-phase and anti-phase in a steady state. By observing entrainment between the asymmetric oscillators we demonstrate the existence of coupling between the two actuators. We qualitatively explain the origin of the synchronized motion using a theoretical model and numerical simulations, which suggest that the motion can be tuned by the mechanical properties of the coupling joint. We thus anticipate that the complex synchronization phenomena usually observed in rigid systems can also exist in soft polymeric materials. This enables the use of new stimuli, featuring a first example of collective motion by photo-actuation.

Carbon Nanotubes Transform Soft Gellan Gum Hydrogels into Hybrid Organic–Inorganic Coatings with Excellent Cell Growth Capability

Carbone nanotubes (CNTs) possess distinct properties, for example, hardness, which is very complementary to biologically relevant soft polymeric and protein materials. Combining CNTs with bio-interfaces leads to obtaining new materials with advanced properties. In this work, we have designed novel organic-inorganic hybrid coatings by combining CNTs with gellan gum (GG) hydrogels. The surface topography of the samples is investigated using scanning electron microscopy and atomic force microscopy. Mechanical properties of synthesized hybrid materials are both assessed at the macro-scale and mapped at the nanoscale. A clear correlation between the CNT concentration and the hardness of the coatings is revealed. Cell culture studies show that effective cell growth is achieved at the CNT concentration of 15 mg/mL. The presented materials can open new perspectives for hybrid bio-interfaces and can serve as a platform for advanced cell culture.

Epoxy Functional Composites Based on Lanthanide Metal–Organic Frameworks for Luminescent Polymer Materials

The integration of metal-organic frameworks (MOF) into organic polymers represents a direct and effective strategy for developing innovative composite materials that combine the exceptional properties of MOFs with the robustness of organic polymers. However, the preparation of MOF@polymer hybrid composites requires an efficient dispersion and interaction of MOF particles with polymer matrices, which remains a significant challenge. In this work, a new simple and direct approach was applied for the development of Ln-MOF@polymer materials. A series of Ln-MOF@TGIC composites {Ln-MOF = [Ln(μ3-BTC)(H2O)6]n (Ln-BTC), where Ln = Eu, Tb, Eu0.05Tb0.95; H3BTC = 1,3,5-benzenetricarboxylic acid; TGIC = triglycidyl isocyanurate} were successfully obtained by applying a grinding method via the chemical bonding between uncoordinated carboxylate groups in Ln-BTC and epoxy groups in TGIC. The Ln-BTC@TGIC materials possess significant fluorescence characteristics with superior emission lifetimes and quantum yields if compared to parent Ln-MOFs. Interestingly, under the UV irradiation, a considerable color change from yellow in Eu0.05Tb0.95-BTC to red in Eu0.05Tb0.95-BTC@TGIC was observed. The energy-transfer mechanism was also rationalized by the density functional theory (DFT) calculations. The developed Ln-BTC@TGIC composites were further applied as functional fluorescent coatings for the fabrication, via a simple spraying method, of the flexible polyimide (PI) films, Ln-BTC@TGIC@PI. Thus, the present work unveils a new methodology and expands its applicability for the design and assembly of stable, multicomponent, and soft polymer materials with remarkable fluorescence properties.

Multicolor Fluorescent Polymeric Actuator with Self‐Sustained Oscillation Behavior

AbstractSoft fluorescent polymeric films are receiving increasing attention in the fields of sensing, display, information encryption, and so on. However, a few attempts are conducted to heterogeneously integrate fluorescent polymeric films with other soft polymeric materials into topology‐optimized architectures (e.g., bilayer and pattern), which may lead to as‐yet‐unimagined performance. Herein, the synthesis of novel multicolor fluorescent polymeric films is presented via dynamic lanthanide coordination, followed by the fabrication of bilayer actuators with unique self‐sustained oscillation behavior. The polymeric films are prepared from polydimethylsiloxane (PDMS) oligomer containing 2,6‐pyridinediimine ligands that can chelate with Eu3+/Tb3+ ions to trigger vivid red/bluish green fluorescence via antenna effect. After being further interfacially engineered with pan paper, fluorescent bilayer actuators are prepared, which display reversible 2D/3D shape deformation in response to environmental temperature changes owing to the mismatch between thermal expansion abilities of two layers. Interestingly, when placing the bilayer actuator with one end fixed near a constant heat source, quite unique self‐sustained oscillation behavior is observed, which encourages to explore their potential applications as dynamic alarming devices. The present study broadens the list of fluorescent polymeric films and suggests the huge potential of multimaterial integration to develop powerful functional materials with versatile uses.

Mechanics of soft polymeric materials using a fractal viscoelastic model

Soft materials are known for their plethora of biomedical applications, intricate structure–property correlation and nonlinear mechanical response. Multiple length–time scale phenomena and hierarchical structure results in their nonlinearity. Phenomenological and continuum mechanical models have been developed to predict their mechanics, which have mostly been very material-specific with inability to predict the mechanics of different types of soft materials simultaneously. This shortcoming has been addressed in the present work, wherein a generic nonlinear viscoelastic model has been proposed to predict the mechanical response of hydrogels, sponges, and xerogels. A fractal derivative viscoelastic model is proposed considering a fractal Maxwell model in parallel with a nonlinear spring. In particular, this model is chosen to qualitatively mimic the material nonlinearity inherent in soft materials. The fractal dashpot in combination with the nonlinear spring accounts for the power law time-dependent rheology of generic soft materials. These two different aspects in the form of nonlinear stiffness and non-Newtonian rheology account for mechanics of most soft materials. The present model is shown to fit well the existing literature results for mechanical response of a multitude of soft material classes with different test conditions and loading rates, which is one of the salient features of the model, apart from its simplistic mathematical framework. Further, a parametric study is reported on the mechanics of nanocellulose loaded poly(vinyl alcohol) xerogel. The model predictions are observed to be in conjunction with the experimental observations.

Multifunctional sub-100 µm thickness flexible piezo/triboelectric hybrid water energy harvester based on biocompatible AlN and soft parylene C-PDMS-Ecoflex™

Nanogenerators have emerged recently as a new technology for harvesting energy from renewable and clean energy sources. Water in nature carries high amounts of kinetic and electrostatic energy; it is ubiquitous and widely accessible in different forms: i.e. as droplets, flows or waves. Either piezoelectric or triboelectric nanogenerators (PENGs, TENGs) have been shown to be effective for harvesting energy from liquids and ocean but the integration of both transduction mechanisms in a single hybrid device allows to exploit several operating conditions and to optimize performances, overcoming the limits of single components. Current piezo-tribo hybrid devices are mostly based on scarcely durable polymers or thick lead-based ceramic materials. Additionally, they are often limited to a specific application or environment due to their architecture and employed materials. In this work, a multifunctional, flexible and conformal hybrid nanogenerator (HNG) has been developed with a sub-100 µm thickness and with a novel combination of biocompatible thin-film piezo-ceramic and soft polymeric materials, for harvesting energy of different water sources, i.e. impacts, raindrops and buoying waves. The PENG component is based on a double-sided metallized AlN thin film, sputtered on polyimide. The TENG component is made of a metallized porous patch made of a mixture of PDMS and platinum-catalyzed silicone (Ecoflex™), encapsulated by a friction film of Parylene C surface-treated with UV/ozone. As a result, the HNG exhibits non-algebraic enhanced performances: the resulting power densities under tapping are ~ 6.5 mW/m 2 for PENG, 65 mW/m 2 for TENG, ~ 230 mW/m 2 for HNG. Multifunctionality is demonstrated by harvesting energy from different water-conveyed sources (i.e. impacts/breakwaters, raindrops, buoying waves). In particular, the device shows optimal and reliable energy harvesting performance under strong impulsive impacts (~ 0.8 W/m 2 ) and raindrops impacts (~ 9 mW/m 2 ). A custom buoyant device, called piezo-JellyFish (pJF), is proposed to exploit the HNGs for harvesting wave energy, based on a connection of three HNGs acting as oral arms: this system yields ~ 3.2 mW/m 2 , with 3 cm-amplitude standing waves. Finally, the HNG exhibits optimal adhesion on the skin and can be also used for monitoring human motions, revealing its multifunctionality also as a wearable conformal sensor. • The hybridization of piezoelectric and triboelectric nanogenerators is effective and allows to enhance performances. • A multifunctional, sub-100 µm thickness, flexible and conformal hybrid nanogenerator is developed for water energy harvesting. • The HNG is based on a novel combination of biocompatible thin-film AlN and soft parylene–PDMS–Ecoflex. • The HNG exhibits enhanced performances for tapping, impacts, raindrops and water waves, through a piezo-JellyFish system. • The HNG exhibits optimal skin-adhesion, revealing its multifunctionality as a wearable conformal sensor.

Multifunctionality in Polymer Networks by Dynamic of Coordination Bonds

AbstractThe need for multifunctional materials is driven by emerging technologies and innovations, such as in the field of soft robotics and tactile or haptic systems, where minimizing the number of operational components is not only desirable, but can also be essential for realizing such devices. This study report on designing a multifunctional soft polymer material that can address a number of operating requirements such as solvent resistance, reshaping ability, self‐healing capability, fluorescence stimuli‐responsivity, and anisotropic structural functions. The numerous functional abilities are associated to rhodium(I)–phosphine coordination bonds, which in a polymer network act with their dynamic and non‐covalently bonded nature as multifunctional crosslinks. Reversible aggregation of coordination bonds leads to changes in fluorescence emission intensity that responds to chemical or mechanical stimuli. The fast dynamics and diffusion of rhodium–phosphine ions across and through contacting areas of the material provide for reshaping and self‐healing abilities that can be further exploited for assembly of multiple pieces into complex forms, all without any loss to material‐sensing capabilities.

Biomimetic Soft Polymer Microstructures and Piezoresistive Graphene MEMS Sensors Using Sacrificial Metal 3D Printing.

Recent advances in 3D printing technology have enabled unprecedented design freedom across an ever-expanding portfolio of materials. However, direct 3D printing of soft polymeric materials such as polydimethylsiloxane (PDMS) is challenging, especially for structural complexities such as high-aspect ratio (>20) structures, 3D microfluidic channels (∼150 μm diameter), and biomimetic microstructures. This work presents a novel processing method entailing 3D printing of a thin-walled sacrificial metallic mold, soft polymer casting, and acidic etching of the mold. The proposed workflow enables the facile fabrication of various complex, bioinspired PDMS structures (e.g., 3D double helical microfluidic channels embedded inside high-aspect ratio pillars) that are difficult or impossible to fabricate using currently available techniques. The microfluidic channels are further infused with conductive graphene nanoplatelet ink to realize two flexible piezoresistive microelectromechanical (MEMS) sensors (a bioinspired flow/tactile sensor and a dome-like force sensor) with embedded sensing elements. The MEMS force sensor is integrated into a Philips 9000 series electric shaver to demonstrate its application in “smart” consumer products in the future. Aided by current trends in industrialization and miniaturization in metal 3D printing, the proposed workflow shows promise as a low-temperature, scalable, and cleanroom-free technique of fabricating complex, soft polymeric, biomimetic structures, and embedded MEMS sensors.

Multilayered structural design of flexible films for smart thermal management

Intelligent materials have the ability to sense the environment and respond to their surrounding accordingly. Herein, the thermally conductive hybrid films were intellectualized by using activated shape memory composite as matrix, which endows hybrid films with active heat dissipation behavior. The obtained hybrid films not only visualize the temperature of the device by the change of shape, but also further improve thermal management abilities through the increase of contact area of the films with air in the shape changing process. The hybrid films also show high thermal conductivity because the multilayered structure was designed and constructed through the method of evaporation-induced self-assembly followed by hot-pressing technology. With the same content of graphene nanosheets, thermal conductivities of hybrid films are increased with the increase of layers. Five layered hybrid film shows the highest thermal management abilities and achieves the thermal conductivity as high as 19.37 W·m−1·K−1, which is 79.4% higher than single layered hybrid film. The structure design of hybrid films and their intellectualization opens up a new direction to improve thermal management effect of soft polymeric materials.

A Review on Graphene Oxide Two-dimensional Macromolecules: from Single Molecules to Macro-assembly

Graphene oxide (GO), which consists of two-dimensional (2D) sp2 carbon hexagonal networks and oxygen-contained functional groups, has laid the foundation of mass production and applications of graphene materials. Made by chemical oxidation of graphite, GO is highly dispersible or even solubilized in water and polar organic solvents, which resolves the hard problem of graphene processing and opens a door to wet-processing of graphene. Despite its defects, GO is easy to functionalize, dope, punch holes, cut into pieces, conduct chemical reduction, form lyotropic liquid crystal, and assemble into macroscopic materials with tunable structures and properties as a living building block. GO sheet has been viewed as a single molecule, a particle, as well as a soft polymer material. An overview on GO as a 2D macromolecule is essential for studying its intrinsic properties and guiding the development of relevant subjects. This review mainly focuses on recent advances of GO sheets, from single macromolecular behavior to macro-assembled graphene material properties. The first part of this review offers a brief introduction to the synthesis of GO molecules. Then the chemical structure and physical properties of GO are presented, as well as its polarity in solvent and rheology behavior. Several key parameters governing the ultimate stability of GO colloidal behavior, including size, pH and the presence of cation in aqueous dispersions, are highlighted. Furthermore, the discovery of GO liquid crystal and functionalization of GO molecules have built solid new foundations of preparing highly ordered, architecture-tunable, macro-assembled graphene materials, including 1D graphene fibers, 2D graphene films, and 3D graphene architectures. The GO-based composites are also viewed and the interactions between these target materials and GO are carefully discussed. Finally, an outlook is provided in this field, where GO is regarded as macromolecules, pointing out the challenges and opportunities that exist in the field. We hope that this review will be beneficial to the understanding of GO in terms of chemical structure, molecular properties, macro-assembly and potential applications, and encourage further development to extend its investigations from basic research to practical applications.

The Dynamic Viscoelasticity of Dental Soft Polymer Material Containing Citrate Ester-Based Plasticizers.

The aim of this study was to investigate the dynamic viscoelasticity of dental soft polymer material containing citrate ester-based plasticizers. Three kinds of citrate ester-based plasticizer (Citroflex® C-2: TEC, Citroflex® A-2: ATEC, and Citroflex® A-4: ATBC), with the combination of 5 wt% ethyl alcohol, were used as the liquid phase. The dynamic viscoelastic properties of nine ethyl methacrylate polymers: (A, B, C, D, E, F, G, H, and I) were immersed in 37 °C distilled water for 0, 1, 3, 7, 14 and 30 days, respectively. The dynamic viscoelastic properties were measured at 37 °C with an automatic dynamic mechanical analyzer. The shear storage modulus (G′), shear loss modulus (G″), and loss tangent (tan δ) were determined at 1 Hz. These parameters were statistically analyzed by two-way and one-way ANOVA and Tukey’s multiple comparison test at a predetermined significance level of 0.05. A significant difference was found among the materials in terms of the dynamic viscoelasticity. The materials containing citrate ester-based plasticizer ATBC showed the most stable dynamic viscoelasticity. Considering the limitations of this study, the results suggest that the inclusion of citrate ester-based plasticizer can improve the durability of dental soft polymer materials.

Формування розподілення конусних поверхонь у структурі оптичних дифузорів-гомогенізаторів

An analysis and research of formation of random and regular relief structures in optical diffusers-homogenizers are carried out. The features of the methods for manufacturing optical diffusers are considered too. The implementation of the formation of random relief structures in optical diffusers is proposed.The optical diffusers are widely used in beam guidance systems, remote control of complex industrial processes, lighting systems for various industrial applications and in other devices where there is a need to form a lighting beam with specified parameters. Unlike conventional frosted glass, the optical diffusers-homogenizers allow one to control the width of the light scattering indicator for more efficient use of the light beam in guidance systems.There are different methods of manufacturing optical diffusers, depending on the final purpose of use, including the conversion of amplitude holographic recording in relief-phase on halogen-silver photoemulsions, the formation of holographic structures on the surface of the photoemulsion in the form of relief indentation of the film layer on the layer of acrylic resin with the formation of a series of evenly distributed convex microspots on the layer of acrylic resin.The proposed methods have certain disadvantages with respect to their use in the guidance systems. The optical diffuser is made of soft polymeric material, which complicates its operation. Therefore, improving the methods of manufacturing optical diffusers remains an urgent task To solve this problem, a method of manufacturing an optical diffuser in the form of a relief microstructure is proposed, including the application of a hard-alloy conical indenter with an apex angle of 120–160° conical depressions on a metal substrate, which is later used as a stamp for thermal pressing of a relief microstructure in the form of conical protrusions on an optically transparent polymer material.To achieve high efficiency during homogenization and to avoid the appearance of a zero-order spot, the optical elements created by conical surfaces have to be structured with a fill factor of 100 %.The analysis and research of the formation of the distribution of conical surfaces in the structure of optical diffusers-homogenizers to obtain the most homogeneous structure of the light flux at the sites of the photodetector have been widely presented. Fig.: 7. Refs: 6 titles.

Azobenzene Based Photo-responsive Mechanical Actuator Fabricated by Intermolecular H-bond Interaction

Photo-responsive mechanical actuator is a class of stimuli-responsive materials transferring light to mechanical energy through macroscopic transformation. To fabricate photo-responsive mechanical actuator, soft polymeric materials crosslinked with functional bridging structures are desired. Supramolecular interaction is a relatively common way to fabricate crosslinked materials due to its excellent self-assembly performance. And azobenzene and derivatives are ideal candidates of photo-responsive materials because of the unique photo-induced trans-cis isomerization. Here, a new kind of crosslinked materials based on supramolecular interaction between 4,4′-dihydroxyazobenzene and chitosan is reported. Under 355 nm irradiation, the macroscopic bending of polymeric materials occurs rapidly due to the photo-isomerization of 4,4′-dihydroxyazobenzene. Meanwhile, the photo-responsive mechanical actuator can also lift weight which is up to 200 times that of the actuator itself, and convert energy from light to mechanical work efficiently. This report suggests a new kind of photo-responsive actuator based on supramolecular interaction and may be helpful to contribute a theoretical basis to the design and synthesis of photo-responsive mechanical actuator suitable for large-scale manufacturing industrialization in future.

Near-hysteresis-free soft tactile electronic skins for wearables and reliable machine learning.

Electronic skins are essential for real-time health monitoring and tactile perception in robots. Although the use of soft elastomers and microstructures have improved the sensitivity and pressure-sensing range of tactile sensors, the intrinsic viscoelasticity of soft polymeric materials remains a long-standing challenge resulting in cyclic hysteresis. This causes sensor data variations between contact events that negatively impact the accuracy and reliability. Here, we introduce the Tactile Resistive Annularly Cracked E-Skin (TRACE) sensor to address the inherent trade-off between sensitivity and hysteresis in tactile sensors when using soft materials. We discovered that piezoresistive sensors made using an array of three-dimensional (3D) metallic annular cracks on polymeric microstructures possess high sensitivities (> 107 Ω ⋅ kPa-1), low hysteresis (2.99 ± 1.37%) over a wide pressure range (0-20 kPa), and fast response (400 Hz). We demonstrate that TRACE sensors can accurately detect and measure the pulse wave velocity (PWV) when skin mounted. Moreover, we show that these tactile sensors when arrayed enabled fast reliable one-touch surface texture classification with neuromorphic encoding and deep learning algorithms.

Drying kinetics and acoustic properties of soft porous polymer materials

We describe a method for the fabrication of acoustic metasurfaces, which is based on soft porous polymer materials. The materials are obtained using an emulsion templating technique, which allows for the fabrication of soft porous polymers with fully controlled porosity values between 0 and 30%. Our approach involves the polymerization of water-in-silicone emulsions with controlled water volume fractions. The obtained wet solid monolith samples are dried using three different methods. Due to the softness of the polymer matrix, and like in polyHIPE hydrogels or silica aerogels, the first method—regular air drying—leads to a collapse of the material and we present a complete experimental study of the observed kinetics as well as a model to account for the observed results. We show that this model can catch the kinetics characteristics. Then, using two alternative drying techniques, H2O2-assisted and supercritical drying, we show that it is possible to obtain materials with fully controlled porosities. The speed of sound—or equivalently the material acoustic index—inside the material being dependent on its porosity, we obtain a gradient-index acoustic material by spatially controlling the porosity distribution along the two dimensions of these metasurfaces. Their ability in terms of wavefront shaping is then demonstrated through a deflecting experiment performed in water with a sample having a thickness five times smaller than the incident acoustic wavelength at ultrasonic frequencies.

Magic-angle-spinning-induced local ordering in polymer electrolytes and its effects on solid-state diffusion and relaxation NMR measurements.

Magic-angle-spinning (MAS) enhances sensitivity and resolution in solid-state nuclear magnetic resonance (NMR) measurements. MAS is obtained by aerodynamic levitation and drive of a rotor, which results in large centrifugal forces that may affect the physical state of soft materials, such as polymers, and subsequent solid-state NMR measurements. Here, we investigate the effects of MAS on the solid-state NMR measurements of a polymer electrolyte for lithium-ion battery applications, poly(ethylene oxide) (PEO) doped with the lithium salt LiTFSI. We show that MAS induces local chain ordering, which manifests itself as characteristic lineshapes with doublet-like splittings in subsequent solid-state 1 H, 7 Li, and 19 F static NMR spectra characterizing the PEO chains and solvated ions. MAS results in distributions of stresses and hence local chain orientations within the rotor, yielding distributions in the local magnetic susceptibility tensor that give rise to the observed NMR anisotropy and lineshapes. The effects of MAS were investigated on solid-state 7 Li and 19 F pulsed-field-gradient (PFG) diffusion and 7 Li longitudinal relaxation NMR measurements. Activation energies for ion diffusion were affected modestly by MAS. 7 Li longitudinal relaxation rates, which are sensitive to lithium-ion dynamics in the nanosecond regime, were essentially unchanged by MAS. We recommend that NMR researchers studying soft polymeric materials use only the spin rates necessary to achieve the desired enhancements in sensitivity and resolution, as well as acquire static NMR spectra after MAS experiments to reveal any signs of stress-induced local ordering.

Realization of Open Software Chain for 3D Modeling and Printing of Organs in Simulation Centers: Example of Renal Pelvis Reconstruction

Three-dimensional (3D) printing has many uses in healthcare such as in surgical training. It is becoming an interesting tool finding new pedagogical purposes in medical simulation. In this study, using a process consisting of 3D modeling, a simulator dedicated to pyeloplasty was designed, manufactured, and evaluated by experts. With the aid of open-source software and computer-aided design software, 3D models of a renal parenchyma, a renal pelvis and a ureter were created. This renal apparatus was processed and crafted with additive manufacturing using soft polymer materials. Polyvinyl alcohol material was used to print the components in order to make them dissectible and to evaluate their use in surgical teaching. Seven expert surgeons evaluated the model by performing a pyeloplasty sequence established in a previous work. An evaluation grid with 8 items related to surgical movement was rated on a 5-point Likert scale to assess how similar working with the model was to actual surgery. Three items were rated with a score greater than or equal to 4 (Needle penetration, Thread-sliding, and Cutting Strength). Suture strength was rated with a score above 3.5 for both renal pelvis and ureter, whereas elasticity was rated below 3. Handling and mobility properties were rated above 3 for the renal pelvis and below 3 for the ureter. The cost of the unit was $0.30 per renal unit. The primary difference identified was a difference in elongation between polyvinyl alcohol material and real biological tissue. It is feasible to generate and print a low cost upper urinary tract model from patient data imagery using environmentally friendly products that can be used effectively in surgical training. The simulator has been able to reproduce sensations related to surgical movements for a low cost. Hereafter, research into the pedagogical benefits provided to students, and through them, patients, should be performed. 3D printing models can offer new opportunities for healthcare simulation specific to different surgical fields.

Soft Printable Electrode Coating for Neural Interfaces.

The mechanical mismatch between implantable interfaces and neural tissues may be reduced by employing soft polymeric materials. Here, we report on a simple strategy to prepare and pattern a soft electrode coating of neural interfacing devices based on a screen-printable conducting hydrogel. The coating formulation, based on polyacrylamide and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, is suitable to additive manufacturing and exhibits excellent adhesion to polydimethylsiloxane, an elastomer commonly used as a substrate in soft neural interfaces. The soft conductive coating displays a tunable elastic modulus in the 10-100 kPa range and electrochemical properties on a par with stiff conductive inks while supporting good neural cell attachment and proliferation in vitro. Next, the soft printable hydrogel is integrated within a 4 × 4 microelectrode array for electrocorticography with 250 μm-diameter contacts. Acute recording of cortical local field potentials and electrochemical characterization preimplantation and postimplantation highlight the stability of the soft organic conductor. The overall robustness of the soft coating and its patterning method provide a promising route for a range of implantable bioelectronic applications.