Compliant Interface Research Articles

An Open Science oriented Bayesian interpolation model for marine parameter observations

Ecological and ecosystem modellers frequently need to interpolate spatiotemporal observations of geophysical and environmental parameters over an analysed area. However, particularly in marine science, modellers with low expertise in oceanography and hydrodynamics can hardly use interpolation methods optimally. This paper introduces an Open Science oriented, open-source, scalable and efficient workflow for 2D marine environmental parameters. It combines a fast, efficient interpolation method with a Bayesian hierarchical model embedding the stationary advection–diffusion equation as a constraint. Our workflow fills the usability gap between interpolation software providers and the users’ communities. It can run entirely automatically without requiring expert parametrisation. It is also available on a cloud computing platform, with a Web Processing Service compliant interface, supporting collaboration, repeatability, reproducibility, and provenance tracking. We demonstrate that our workflow produces comparable results to a state-of-the-art model (frequently used in oceanography) in interpolating four environmental parameters at the global scale.

Open Geospatial System for LUCAS In Situ Data Harmonization and Distribution

The use of in situ references in Earth observation monitoring is a fundamental need. LUCAS (Land Use and Coverage Area frame Survey) is an activity that has performed repeated in situ surveys over Europe every three years since 2006. The dataset is unique in many aspects; however it is currently not available through a standardized interface, machine-to-machine. Moreover, the evolution of the surveys limits the performance of change analysis using the dataset. Our objective was to develop an open-source system to fill these gaps. This paper presents a developed system solution for the LUCAS in situ data harmonization and distribution. We have designed a multi-layer client-server system that may be integrated into end-to-end workflows. It provides data through an OGC (Open Geospatial Consortium) compliant interface. Moreover, a geospatial user may integrate the data through a Python API (Application Programming Interface) to ease the use in workflows with spatial, temporal, attribute, and thematic filters. Furthermore, we have implemented a QGIS plugin to retrieve the spatial and temporal subsets of the data interactively. In addition, the Python API includes methods for managing thematic information. The system provides enhanced functionality which is demonstrated in two use cases.

Spatiotemporal characterization of turbulent channel flow with a hyperelastic compliant wall

Direct numerical simulations of turbulent flow in a channel with one rigid and one viscoelastic wall are performed. An Eulerian–Eulerian model is adopted with a level-set approach to identify the fluid–compliant material interface. Focus is placed on the propagation of Rayleigh waves in the compliant material, whose speed depends on the shear modulus of elasticity and whose dominant wavelength depends on the thickness of the viscoelastic layer. These parameters are selected to ensure coupling between the compliant surface and turbulence. When the phase speed of Rayleigh waves is commensurate with the advection velocity of near-wall pressure fluctuations, sheets of vorticity are lifted up and detached near the critical layer and lead to a local pressure minimum. These events are caused by the inflectional velocity profile near the troughs, and are controlled by the net vorticity flux at the elastic surface. This phenomenon is central to understanding the statistical characteristics of the flow, including the surface deformation–pressure correlation and enhanced stochastic Reynolds shear stresses. Finally, we discuss the influence of three-dimensionality of the surface topography on the generation of streamwise vorticity, secondary motions and lateral turbulent transport.

Enabling Fast Exploratory Analyses Over Voluminous Spatiotemporal Data Using Analytical Engines

Fueled by the proliferation of IoT devices and increased adoption of sensing environments the collection of spatiotemporal data has exploded in recent years. Disk based storage systems provide reliable archives but are far too slow for efficient analytics and spatiotemporal datasets quickly exceed the memory capacity of cluster environments. Current solutions focused on in-memory analytics suffer from memory contention and unnecessary network I/O, failing to provide a suitable platform for iterative, exploratory analytics in shared environments. In this work we propose Anamnesis, the first in-memory, sketch aligned, HDFS compliant storage system. Data sketching algorithms reduce dataset sizes by summarizing feature values and inter-feature relationships. Anamnesis leverages data sketches to alleviate memory contention and vastly reduce network I/O during analytics. Upon request, we generate accurate full-resolution datasets with negligible resource and time costs. Datasets are available using a fully HDFS compliant interface allowing Anamnesis to achieve unprecedented compatibility with popular analytics engines. This facilitates adoption into existing workflows by serving as a drop-in replacement for canonical HDFS. We evaluate the system using 2 spatiotemporal datasets, a variety of popular analytics engines, and real-world analytical operations.

Approach for Calibrated Measurement of the Frequency Response for Characterization of Compliant Interface Elements on Vibration Test Benches

In vibration tests, the behavior of the structure depends on its mechanical boundary conditions, which are represented in physical tests by connecting elements with mechanical properties. Adjustable impedance elements are machine elements fulfilling the task of an adjustable connection on a vibration test bench and therefore represent a variety of properties. Their mechanical properties must be known over wider ranges than comparable compliant structures tested in the literature. This paper is dedicated to vibration testing of the adjustable impedance elements themselves, taking the influences of fixtures and measuring devices of the test bench into account. Different approaches for measuring the frequency response functions are applied to freely vibrating masses at a hydraulic and an electrodynamic test bench. Mass cancellation and the frequency-dependent measurement systems function have shown their usefulness in characterizing the biodynamic response of hand–arm models before. This measurement method is extended to be transferable to machine elements to obtain reliable results under a wider range of test conditions. The necessity for dynamically calibrated measurement of the frequency response functions is demonstrated for different free vibration masses and for two compliant elements on two different test benches to provide results over a wide range of test conditions.

The effect of a novel pillar surface morphology and material composition demonstrates uniform osseointegration

Long-term survival of orthopedic implants requires a strong and compliant interface between the implant and surrounding bone. This paper further explores the in-vivo response to a novel, macro-scale osseointegration surface morphology. In this study, we examine the effects of material composition on osseointegration in relation to the controlled surface geometry. The pillared surface is constructed of discontinuous surface geometry which creates an open space for unencumbered bone migration. In creating an open, macro-scale morphology we have demonstrated a bone migration and integration that is less dependent on the underlying implant material and is substantially driven thru surface geometry.In this in-vivo study an established ovine model was used to examine the effects of implant material composition on bone ingrowth and mechanical performance. Cortical and cancellous sites in the tibia and distal femur were examined at 6 and 12 weeks with μCT, histology, histomorphometry, and mechanical performance. Implant materials tested included PEEK (Evonik, VISTAKEEP®), PEEK HA (Invibio, PEEK-OPTIMA HA Enhanced), Titanium coated PEEK, Titanium (Ti–6Al–4V, Grade 5), and Ultra-High Molecular Weight Polyethylene (UHMWPE). Extensive bone ingrowth was noted in all implant materials at 12 weeks with maturation of the bone within the pillar structure from 6 weeks to 12 weeks. Histology demonstrated little fibrous deposition at the implant interface with no adverse cellular reactions. Histomorphometric review of cortical sites revealed greater than 60% bone ingrowth at 6 weeks increasing to nearly 80% by the 12 week timepoint. Cancellous sites yielded a mean of 30% ingrowth at 6 weeks increasing to 35% by 12 weeks. Pushout testing of cortical site samples demonstrated increase in pushout force between the 6 and 12 week timepoints. Increases were significant in all but the UHMWPE samples. Stiffness likewise increased in all samples between the two times.These results demonstrated the effectiveness of the pillar morphology with full integrating from the surrounding bony tissue regardless of the material.

Closed-form solutions for modelling the rotational stiffness of continuous and discontinuous compliant interfaces in two-layer Timoshenko beams

An analytical model for a two-layer Timoshenko beam with a compliant interface is presented. A family of closed-form solutions is given for several cases of contact conditions at the interface that can include or exclude interlayer slip and relative rotations of the layers’ cross sections (distortion), with particular attention devoted to the latter. Each kinematic field at the interface is related to a corresponding traction by means of a linear-elastic law. The novelty of the proposed model is the rotational stiffness at the interface, completely separate from the tangential stiffness, that can control the amount of interlayer distortion at the interface. The derived closed-form solutions allow an exact stiffness matrix for any case of admissible boundary conditions to be obtained, as well as for continuity conditions in the case where multiple elements with closed-form solutions are mutually connected. The application of the closed-form solutions for continuous interface (adhesive joints) or for discontinuous interface (shear connectors or adhesive defects) is presented. Accuracy and applicability of the closed-form solutions have been assessed in two representative numerical examples allowing to conclude that the rotational stiffness at the interface can strongly affect the behaviour of a two-layer beam.

Elastic, Conductive, and Mechanically Strong Hydrogels from Dual-Cross-Linked Aramid Nanofiber Composites.

Recent research on conductive hydrogels has revealed their potential for building advanced soft bioelectronic devices. Their mechanical flexibility, water content, and porosity approach those of biological tissues, providing a compliant interface between the human body and electronic hardware. Conductive hydrogels could be utilized in many soft tools such as neural electrodes, tactile interfaces, soft actuators, and other electroactive devices. However, most of the available conductive hydrogels exhibit weak mechanical properties, which hinders their application in durable biointegrated systems. Here, we report aramid nanofiber-based hydrogels providing a combination of high elasticity, strength, and electrical conductivity. Highly branched aramid nanofibers (ANFs) provide a robust three-dimensional (3D) framework resembling those in load-bearing soft tissues. When interlaced with poly(vinyl alcohol) (PVA) and cross-linked with both noncovalent and covalent interactions, the nanofiber composites exhibit a high water content of ∼76.4 wt %, strength of ∼7.5 MPa, ductility of ∼407%, and shape recovery of ∼99.5% under cyclic tensile stress of 0.3 MPa. Mobile ions impart a conductivity of ∼2 S/m to the hydrogels, enabling large-strain sensors with stable operation. In addition, the embedded silver nanoparticles afford broad-spectrum antimicrobial activities, which is favorable for medical devices. The versatility of aramid nanofiber-based composites suggests their further possibilities for functionalization and scalable fabrication toward sophisticated bioelectronic systems.

Effects of heat treatment on microstructure and mechanical properties of 2.5D Cf/BN/pyrocarbon composites by chemical vapor infiltration

In this study, 2.5D carbon fiber reinforced pyrocarbon matrix composites with a BN interphase (Cf/BN/PyC) were prepared by chemical vapor infiltration. Through comparing the distribution of thermal residual stress and the evolution of the interface microstructure of composite before and after heat treatment, the reason why the structure and orientation of the BN interphase in the Cf/BN/PyC composite deviate from the layered structure required for the expected compliant interface was analyzed. The results show that the crystalline skin of Cf affects the order of BN near the Cf/BN interface, thereby forming BN interphase with a structural gradient from the beginning. The infiltration process of pyrocarbon interacts with the growth and rearrangement process of BN, resulting in incomplete crystallization of BN. After heat treatment at 1600°C, BN interphase with high crystallinity in the nano-domain but disordered orientation is formed, although it can also debond the interface according to He and Hutchinson's model. The BN grain orientation deviates from the fiber axis mainly due to multi-factor coupling, in which the axial residual thermal stress generated at the Cf/BN/PyC interface is the main influencing factor. Understanding the influence of the heat treatment (HT) on the atomic-domain orientation change and structural evolution during the preparation of boron nitride (BN) interphase by chemical vapor infiltration paves us an effective way to modify the preparation of interphase with low fracture energy.

Design of a low-cost tactile robotic sleeve for autonomous endoscopes and catheters

Recent developments in medical robotics have been significant, supporting the minimally invasive operation requirements, such as smaller devices and more feedback available to surgeons. Nevertheless, the tactile feedback from a catheter or endoscopic type robotic device has been restricted mostly on the tip of the device and was not aimed to support the autonomous movement of the medical device during operation. In this work, we design a robotic sheath/sleeve with a novel and more comprehensive approach, which can function for whole body or segment-based feedback control as well as diagnostic purposes. The robotic sleeve has several types of piezo-resistive pressure and extension sensors, which are embedded at several latitudes and depths of the silicone substrate. The sleeve takes the human skin as a biological model for its structure. It has a better tactile sensation of the inner tissues in the torturous narrow channels such as cardiovascular or endoluminal tracts in human body and thus can be used to diagnose abnormalities. In addition to this capability, using the stretch sensors distributed alongside its body, the robotic sheath/sleeve can perceive the ego-motion of the robotic backbone of the catheter and can act as a position feedback device. Because of the silicone substrate, the sleeve contributes toward safety of the medical device passively by providing a compliant interface. As an active safety measure, the robotic sheath can sense blood clots or sudden turns inside a channel and by modifying the local trajectory and can prevent embolisms or tissue rupture. In the future, advanced manufacturing techniques will increase the capabilities of the tactile robotic sleeve.

Effective medium modeling of diagenesis impact on the petroacoustic properties of carbonate rocks

Carbonate formations are highly heterogeneous, and the velocity-porosity relationships are controlled by various microstructural parameters, such as the types of pores and their distribution. Because diagenesis is responsible for important changes in the microstructure of carbonate rocks, we have extended the standard effective medium approach to model the impact of diagenesis on the carbonate elastic properties through a step-by-step effective medium modeling. Two different carbonate rocks deposited, respectively, in lacustrine and marine environments are considered in this study. The first key step is the characterization of the diagenesis, which affected the two studied carbonate sample sets. Effective medium models integrating all of the geologic information accessible from petrographic analysis are then built. The evolution of the microstructural parameters during diagenesis is thoroughly constrained based on an extensive experimental data set, including X-ray diffraction analysis, different porosimetry methods, and ultrasonic velocity measurements. A new theoretical approach including two sources of compliance is developed to model the specific behavior of carbonates. A compliant interface is introduced around the main carbonate grains to represent grain contacts and the different pore scales are taken into account through multiscale modeling. Finally, direct calculations with the model provide elastic wave velocities representative of the different diagenetic stages. An extrapolation to permeability evolution is also introduced. This approach allows the identification of the acoustic signature of specific diagenetic events, such as dolomitization, dissolution, or cementation, and the assessment of their impact on the elastic properties of carbonates.

Binder-free graphene oxide doughs

Graphene oxide (GO) sheets have been used to construct various bulk forms of GO and graphene-based materials through solution-based processing techniques. Here, we report a highly cohesive dough state of GO with tens of weight percent loading in water without binder-like additives. The dough state can be diluted to obtain gels or dispersions, and dried to yield hard solids. It can be kneaded without leaving stains, readily reshaped, connected, and further processed to make bulk GO and graphene materials of arbitrary form factors and tunable microstructures. The doughs can be transformed to dense glassy solids of GO or graphene without long-range stacking order of the sheets, which exhibit isotropic and much enhanced mechanical properties due to hindered sliding between the sheets. GO dough is also found to be a good support material for electrocatalysts as it helps to form compliant interface to access the active particles.

On Stability of Specific Adhesion of Particles to Membranes in Simple Shear Flow.

Adhesion of carrier particles to the luminal surface of endothelium under hemodynamic flow conditions is critical for successful vascular drug delivery. Endothelial cells (ECs) line the inner surface of blood vessels. The effect of mechanical behavior of this compliant surface on the adhesion of blood-borne particles is unknown. In this contribution, we use a phase-plane method, first developed by Hammer and Lauffenburger (1987, "A Dynamical Model for Receptor-Mediated Cell Adhesion to Surfaces," Biophys. J., 52(3), p. 475), to analyze the stability of specific adhesion of a spherical particle to a compliant interface layer. The model constructs a phase diagram and predicts the state of particle adhesion, subjected to an incident simple shear flow, in terms of interfacial elasticity, shear rate, binding affinity of cell adhesive molecules, and their surface density. The main conclusion is that the local deformation of the flexible interface inhibits the stable adhesion of the particle. In comparison with adhesion to a rigid substrate, a greater ligand density is required to establish a stable adhesion between a particle and a compliant interface.

Carbon fiber reinforced ceramic matrix composites with an oxidation resistant boron nitride interface coating

Toughening a ceramic in a ceramic matrix composite (CMC) depends on an ability of the composite to tolerate an accumulation of matrix cracks. When the reinforcement phase is carbon fiber, these cracks leave the fiber susceptible to destructive oxidation by ingress of air during high temperature exposure. Generally, a graphitic carbon interface coating is applied to carbon fibers because it provides for a weak bond between fiber and matrix that is required to promote toughening. This investigation seeks to utilize a BN coating instead of a C coating in order to promote oxidation resistance. Like graphitic carbon, BN is soft and easily cleavable. Preliminary observations that C/BN/SiC CMC's using Toray T300 carbon fibers were highly brittle and of low strength lead to a requirement of heat treating the fibers prior to the CVD of BN for toughened composites to be fabricated. It is likely heat treating removed reactive functionalities from the fiber surface to yield a weakly adhered and compliant interface.

DINA Bits - Small Services Growing in the DINA System

The DINA system (“DIgital information system for NAtural history data”, https://dina-project.net) consists of several web-based services that fulfill specific tasks. Most of the existing services are covering single core features in the collection management system and can be used either as integrated components in the DINA environment, or as stand-alone services. In this presentation single services will be highlighted as they represent technically interesting approaches and practical solutions for daily challenges in collection management, data curation and migration workflows. The focus will be on the following topics: (1) a generic reporting and label printing service, (2) practical decisions on taxonomic references in collection data and (3) the generic management and referencing of related research data and metadata: Reporting as presented in this context is defined as an extraction and subsequent compilation of information from the collection management system rather than just summarizing statistics. With this quite broad understanding of the term the DINA Reports & Labels Service (Museum für Naturkunde Berlin 2018) can assist in several different collection workflows such as generating labels, barcodes, specimen lists, vouchers, paper loan forms etc. As it is based on customizable HTML templates, it can be even used for creating customized web forms for any kind of interaction (e.g. annotations). Many collection management systems try to cope with taxonomic issues, because in practice taxonomy is used not only for determinations, but also for organizing the collections and categorizing storage units (e.g. “Coleoptera hall”). Addressing taxonomic challenges in a collection management system can slow down development and add complexity for the users. The DINA system uncouples these issues in a simple taxonomic service for the sole assignment of names to specimens, for example determinations. This draws a clear line between collection management and taxonomic research, of which the latter can be supported in a separate service. While the digitization of collection data and workflows proceeds, linking related data is essential for data management and enrichment. In many institutions research data is disconnected from the collection specimen data because the type and structure cannot be easily included in the collection management databases. With the DINA Generic Data Module (Museum für Naturkunde Berlin 2017) a service exists that allows for attaching any relational data structures to the DINA system. It can also be used as a standalone service that accommodates structured data within a DINA compliant interface for data management.

Si nanospring films for compliant interfaces

Films comprised of dense arrays of Si nanosprings were studied for their potential as compliant interface layers. The films, fabricated via glancing angle deposition (GLAD), were comprised of 10-µm high Si nanosprings with 4 or 10 coil turns and seed spacings of 900 nm or 1500 nm. Unseeded films with the same height and 4 or 10 coil turns were co-fabricated as the control material. The film mechanical behavior was a combination of the mechanical response of the individual springs and their interactions inside the film, resulting in increasing compressive stiffness with applied stress. The shear stiffness of all types of Si spring films was in the narrow range of 17–27 MPa. On the contrary, depending on coil geometry, the low-stress compressive stiffness could be varied in the broad range of 13–150 MPa. Thus, this class of nanostructured films allows for relatively decoupled normal and shear properties with values comparable to those of soft polymers. Despite that unseeded films have the thinnest coil wire, it was shown that seeding can produce equal or lower film stiffness, while also increasing the resistance to permanent compression at high stresses. Similarly, a capping layer increased the coherency of the films and their resistance to permanent compression without affecting significantly the compressive film stiffness. Capped films with 10-turn coils, with 900-nm seed spacing, provided the most resistance to permanent compression for stresses at least as high as 15 MPa, while maintaining compressive stiffness values that were equivalent to unseeded 10-turn springs. Finally, capped 4-turn springs with 900-nm seed spacing were shown to be the most compliant of all film types, including unseeded films, while also exhibiting the best agreement between film-level stiffness and estimates based on individual spring properties. Therefore, seeding of GLAD springs can produce films with increased resistance to permanent deformation while maintaining the low stiffness of unseeded films.

Controllable load sharing for soft adhesive interfaces on three-dimensional surfaces

For adhering to three-dimensional (3D) surfaces or objects, current adhesion systems are limited by a fundamental trade-off between 3D surface conformability and high adhesion strength. This limitation arises from the need for a soft, mechanically compliant interface, which enables conformability to nonflat and irregularly shaped surfaces but significantly reduces the interfacial fracture strength. In this work, we overcome this trade-off with an adhesion-based soft-gripping system that exhibits enhanced fracture strength without sacrificing conformability to nonplanar 3D surfaces. Composed of a gecko-inspired elastomeric microfibrillar adhesive membrane supported by a pressure-controlled deformable gripper body, the proposed soft-gripping system controls the bonding strength by changing its internal pressure and exploiting the mechanics of interfacial equal load sharing. The soft adhesion system can use up to ∼26% of the maximum adhesion of the fibrillar membrane, which is 14× higher than the adhering membrane without load sharing. Our proposed load-sharing method suggests a paradigm for soft adhesion-based gripping and transfer-printing systems that achieves area scaling similar to that of a natural gecko footpad.

Failure simulation of unidirectional fiber-reinforced ceramic matrix composites based on evolving compliant interfacial debonding model

Damage and failure process of the unidirectional fiber-reinforced ceramic matrix composites (FRCMCs) under tensile stress had been studied by many researchers in theoretical method. But because of some assumptions made in the theoretical model, it canot describe the performance of interface accurately. In this paper, evolving compliant interface (ECI) is employed to describe the properties of weak bonding interface. The ECI can respond the failure of debonding and sliding of interface efficiently. The whole damage evolution process of the material has been simulated by finite element method (FEM) and the stress-strain curve, the space of cracks at saturated state and the stress of components are discussed. The stress-strain curves of several ceramic composites were predicted by the model and compared with the experimental data. The results indicate that the tensile stress-strain curves agree well with the experimental data on consideration of Evolving compliant interfacial debonding model.

Haptic exploration of highly curved compliant surfaces

In this article, a constraint-based controller is developed for two-manifold oriented viscoelastic surfaces that guarantees smooth and compliant haptic rendering. The approach is direct and uses a pseudo-inverse projection of the haptic device end effector onto the virtual surface. The rendering algorithm enables the user to freely move a soft fingertip model along a highly curved deformable surface and perceive surface roughness in the normal direction by feeling a nonlinear contact force. The normal force is governed by a physically based three-dimensional constitutive model, which accounts for both geometric and material nonlinearities. In experimental implementation, the soft fingertip model acts as the compliant haptic interface (robot) and the user manually guides the manipulator to explore the deformable surface properties in real time. The (nonlinear) reaction force normal to the surface is applied at the soft fingertip edge of the fingertip bone (distal phalanx). The robustness of the approach is illustrated by experimental data in rendering highly curved compliant surfaces.

Shape Deposition Manufacturing of a Soft, Atraumatic, and Deployable Surgical Grasper

This paper details the design, analysis, fabrication, and validation of a deployable, atraumatic grasper intended for retraction and manipulation tasks in manual and robotic minimally invasive surgical (MIS) procedures. Fabricated using a combination of shape deposition manufacturing (SDM) and 3D printing, the device (which acts as a deployable end-effector for robotic platforms) has the potential to reduce the risk of intraoperative hemorrhage by providing a soft, compliant interface between delicate tissue structures and the metal laparoscopic forceps and graspers that are currently used to manipulate and retract these structures on an ad hoc basis. This paper introduces a general analytical framework for designing SDM fingers where the desire is to predict the shape and the transmission ratio, and this framework was used to design a multijointed grasper that relies on geometric trapping to manipulate tissue, rather than friction or pinching, to provide a safe, stable, adaptive, and conformable means for manipulation. Passive structural compliance, coupled with active grip force monitoring enabled by embedded pressure sensors, helps to reduce the cognitive load on the surgeon. Initial manipulation tasks in a simulated environment have demonstrated that the device can be deployed though a 15 mm trocar and develop a stable grasp using Intuitive Surgical's daVinci robotic platform to deftly manipulate a tissue analog.