Hybrid Contact Research Articles

Conformal, Ultra‐thin Skin‐Contact‐Actuated Hybrid Piezo/Triboelectric Wearable Sensor Based on AlN and Parylene‐Encapsulated Elastomeric Blend

AbstractFlexible electronics based on piezoelectric/triboelectric devices is an attractive technology for human sensing. Their hybridization overcomes the limitations of single components, resulting in compliant skin sensors with enhanced performances and applicability. Such hybrid devices are typically based on wide‐area scarcely durable polymers or lead‐containing piezoelectric materials; they are often not biocompatible and poorly skin‐adaptable, lacking in multifunctionality. In this work, a novel compliant, conformal hybrid piezoelectric‐triboelectric ultra‐thin wearable sensor made of biocompatible materials is reported. The device is in contact with skin through an ultra‐soft patch covered on both sides by a thin friction parylene film. Its working principle is unprecedently based on three simultaneous, complementary and mutually enhancing effects: piezoelectric, skin‐contact‐actuation, and piezo‐tribo hybrid contact. The device can detect, with high sensitivity and wide measurement range, both the impulsiveness of sudden motions and the slower micro‐friction phenomena due to skin deformations, ensuring a stable and repeatable identification of bio‐signals typical of body movements. The device multifunctionality is shown for identifying gait walking, distinguishing hand gestures with a 5‐sensor system on the hand back, and monitoring human joints motions (neck, wrist, elbow, knee, ankle). The assessed energy harvesting capabilities demonstrate the suitability for fabrication of more complex self‐powered sensing systems.

A Hybrid Contact Model With Experimental Validation

Abstract This brief paper emphasizes on the experimental study of a hybrid contact model combining a traditional physical-based contact model and a data-driven error model in order to provide a more accurate description of a contact dynamics phenomenon. The physical-based contact model is employed to describe the known contact physics of a complex contact case, while the data-driven error model, which is an artificial neural network model trained from experimental data using a machine learning technique, is used to represent the inherent unmodeled factors of the contact case. A bouncing ball experiment is designed and performed to validate the model. The hybrid contact model can duplicate experimental results well, which demonstrates the feasibility and accuracy of the presented approach.

Comparison of Clinical and Topographic Outcomes of Hybrid and Scleral Lenses in Advanced Keratoconus.

Objectives:To evaluate and compare the effects of hybrid contact lenses (HCLs) and mini-scleral contact lenses (MSCLs) on visual acuity, spherical equivalent, topographic astigmatism, and higher-order aberrations (HOAs) in eyes with advanced keratoconus.Methods:We reviewed the medical records of 43 eyes of 27 patients diagnosed with advanced keratoconus fit hybrid contact lenses (AirFlex®) and mini-scleral contact lenses (Mini-misa®). Pre-fitting examinations included best corrected visual acuity (BCVA), spherical equivalent, topographic findings (topographic astigmatism, maximum keratometry, mean keratometry, central corneal thickness, thinnest corneal thickness, and corneal HOAs. Post-fitting examinations included lens corrected visual acuity, spherical equivalent, topographic astigmatism, corneal HOAs, and contact lens-related discomfort symptoms.Results:Mean BCVA (log MAR) improved significantly from 0.65±0.27 to 0.14±0.09 with HCL and 0.58±0.25 to 0.15±0.13 with MSCL (p<0.05). The mean spherical equivalent and topographic astigmatism measurements decreased significantly in both groups (p<0.05). Eight patients in the HCL group experienced lens-related discomfort. Root-mean square HOA decreased significantly in both groups (p<0.05).Conclusion:Significant improvements in visual acuity, spherical equivalent, topographic astigmatism, and HOAs were observed with both lenses. However, higher patient comfort with scleral lenses may lead to higher compliance in patients with advanced keratoconus.

Wheel–rail contact simulation with lookup tables and KEC profiles: a comparative study

This paper describes and compares the use and limitations of two constraint-based formulations for the wheel–rail contact simulation in multibody dynamics: (1) the use of contact lookup tables and (2) the Knife-edge Equivalent Contact constraint method (KEC-method). Both formulations are presented and an accurate procedure to interpolate within the data in the lookup table is also described. Since the wheel–rail constraint contact approach finds difficulties at simultaneous tread and flange contact scenarios, the lookup table method is implemented with a penetration-based elastic contact model for the flange, turning the method into a hybrid (constant in the tread and elastic in the flange) approach. To deal with the two-point contact scenario in the KEC-method, a regularisation of the tread–flange transition allows the use of the constraint approach in the tread and also in the flange. To show the applicability and limitations of both methods, they are studied and compared with special emphasis in the calculation of normal and tangential contact forces. Numerical results are based on the simulation of a two-wheeled bogie vehicle in different case studies that consider irregular tracks and two wheel–rail profiles combinations: profiles that do not show two-point wheel–rail contacts and profiles that do show two-point wheel–rail contacts. Although results show a good agreement between both approaches, the use of the KEC-method is more extensive since it allows to reproduce the wheel-climbing scenario that cannot be simulated with the lookup table method with the hybrid contact approach. It is concluded that simulations with this later method may not be on the safe side.

Self-driven photodetector based on a GaSe/MoSe2 selenide van der Waals heterojunction with the hybrid contact

The restacking of stripped two-dimensional material into a van der Waals heterojunction provides a promising technology for high-performance optoelectronic devices. This paper presents a self-driven photodetector composed of p-GaSe/n-MoSe2. The hybrid contact is directly formed between the electrode and the heterojunction, which considerably improves the photovoltaic effect. In addition, the Schottky barrier between the semiconductor and metal electrodes creates a built-in electric field, which enhances the self-driven performance of the device. The as-fabricated photodetector has the high responsivity of 0.169 A W−1 at zero bias and the specific detectivity of 6.6 × 1011 Jones. When bias was applied, a responsivity of 6.81 A W−1 and a specific detectivity of 2.8 × 1013 Jones have also been obtained. This work demonstrates that selenide van der Waals heterojunctions based on two-dimensional materials have great potential for future electronic and optoelectronic applications.

Clinical Outcome of Hybrid Contact Lenses in Keratoconus.

To report the clinical outcome of hybrid contact lens fitting in keratoconus. A retrospective chart review was performed of keratoconus patients who had been fitted with hybrid contact lenses in one or both eyes. Patients with a history of previous intraocular surgery (except for corneal crosslinking) and relevant concurrent ocular disease limiting visual outcome were excluded. The outcome data at 6-month follow-up included hybrid lens-corrected visual acuity, wearing time, and lens discontinuation. Fifty-four keratoconus patients (102 eyes) were included. Mean visual acuity with habitual correction before hybrid lens fitting was 0.63±0.29 (decimal Snellen). Eyes were fitted with Eyebrid lenses (LCS Laboratories, Caen, France) and SynergEyes lenses (SynergEyes Inc., Carlsbad, CA). Refits were necessary in 13 eyes, because of poor fitting (76.9%) or suboptimal refraction (23.1%). Visual acuity had significantly improved with hybrid lenses (0.93±0.14; P<0.0001). In 37 eyes (37.8%), hybrid lens wear was discontinued within 6 months after lens fitting. Reported issues were discomfort in 27 eyes (73%), handling difficulties in 14 eyes (37.8%) and poor vision in 1 eye (2.7%). Success rate of lens fitting was significantly correlated to cone morphology (P=0.01). New generation hybrid lenses are an appropriate, safe therapeutic option for keratoconus patients. Excellent visual outcomes are achieved in successful fittings, yet a dropout rate of 37.8%-mainly occurring in sagging, more peripheral, cones - still limit their clinical success.

A surface mesh represented discrete element method (SMR-DEM) for particles of arbitrary shape

A surface mesh represented discrete element method (SMR-DEM) for granular systems with arbitrarily shaped particles is presented. The particle surfaces are approximated using contact nodes obtained from surface mesh. A hybrid contact method which combines the benefits of the sphere-to-sphere and sphere-to-surface approaches is proposed for contact detection and force computation. The simple formulation and implementation render SMR-DEM suitable for three-dimensional simulations. Furthermore, GPU parallelization is employed to achieve higher efficiency. Several numerical examples are presented to show the performance of SMR-DEM. It is found that on the particle level the method is accurate and convergent, while on the system level SMR-DEM can effectively model particle assemblies of various regular and complex irregular shapes.

The impact of hybrid contact lenses on keratoconus progression after accelerated transepithelial corneal cross-linking.

To investigate the effect of hybrid contact lenses (HCLs) on keratoconus (KCN) progression after accelerated transepithelial cross-linking (A-TE CXL). Thirty-five eyes of 26 patients who preferred Ultrahealth HCLs for an optical correction after A-TE CXL formed the study group, and 45 eyes of 34 patients who preferred spectacle correction were age- and sex-matched to form the control group. Corrected distance visual acuity (CDVA), maximum keratometry, mean keratometry, apical posterior keratometry, cylindrical power, minimum corneal thickness, keratoconus vertex indices and curvature asymmetry indices obtained by Scheimpflug corneal topography were compared before, 6 and 12months after the procedure. Anterior segment optic coherence tomography (AS-OCT) was performed to measure the apical corneal clearance of HCL-wearing patients. The median pre-CXL CDVA value of the patients in the HCL group was logMAR 0.30 (0.20-1.0), and it was logMAR 0.30 (0.10-1.0) in the spectacle-corrected group. There was a significant increase in CDVA 6 and 12months after CXL procedure in both groups (p < 0.001, 0.003, respectively). The median front curve asymmetry index (FCAsym) significantly improved after A-TE CXL in the HCL group. The pre-CXL and 12th-month topographic comparisons of the spectacle-corrected group revealed no significant difference. In addition, no significant difference was observed between topographic alterations of two groups (p > 0.05). The CDVA significantly improved, and KCN progression was halted in patients wearing HCL 12months after A-TE CXL. Besides, FCAsym indices can be considered for follow-up of the HCL-wearing patients as an assistive parameter to AS-OCT measurements.

Improvement of carrier collection in Si/a-Si:H nanowire solar cells by using hybrid ITO/silver nanowires contacts

Optoelectronic devices based on high aspect ratio nanowires bring new challenges for transparent electrodes, which can be well addressed by using hybrid structures. Here we demonstrate that a composite contact to radial junction nanowire solar cells made of a thin indium-tin oxide (ITO) layer and silver nanowires greatly improves the collection of charge carriers as compared to a single thick ITO layer by reducing the series resistance losses while improving the transparency. The optimization is performed on p-i-n solar cells comprising of dense non-vertical nanowires with a p-doped c-Si core and an ultra-thin a-Si:H absorption layer grown by plasma-enhanced chemical vapor deposition on glass substrates. The optimal hybrid contact developed in this work is demonstrated to increase the solar cell conversion efficiency from 4.3% to 6.6%.

Evaluation of Visual Acuity Outcomes and Corneal Alterations of New Generation Hybrid Contact Lenses in Patients With Advanced Keratoconus.

To evaluate the visual and corneal outcomes of new generation hybrid contact lenses (HCL) in patients with advanced keratoconus. This was a retrospective study undertaken at a single academic center. The study cohort consisted of subjects with advanced keratoconus who had elected not to undergo keratoplasty and were fitted with HCLs. Patients were fitted either with EyeBrid (LCS, Cane, France) or Airflex (SwissLens, Prilly, Switzerland) HCLs. Primary outcome measures included contact lens (CL) drop-out rate, best corrected visual acuity, and corneal endothelial cell density (ECD) measurements at the end of a 6-month HCL wear. ECD was measured using in vivo confocal microscopy (ConfoScan4; Nidek, Tokyo, Japan). One eye per patient was included for statistical purposes. Paired t tests and Wilcoxon signed-rank tests were used for comparative analyses. Thirty-two keratoconic eyes of 32 patients (14M/18F) with a mean age of 25.9 ± 11.5 years were included in the study. All patients were able to continue CL wear for a duration of 6 months. There was a significant improvement in the mean best corrected visual acuity from 0.5 ± 0.2 logarithm of minimal angle of resolution to 0.1 ± 0.1 logarithm of minimal angle of resolution after daily CL wear with HCL at the 6-month follow-up visit (P < 0.001). No vision-threatening CL-related corneal adverse effects were observed. There was no significant reduction in the ECD noted at the 6-month visit [2625.8 ± 300.3 cells/mm (baseline) vs. 2566.4 ± 309.8 cells/mm (6-month); P = 0.623]. Hybrid contact lenses can provide improved visual function without inducing any short-term clinical or microscopic adverse effects on corneal endothelial cells in patients with advanced keratoconus.

Use of new-generation hybrid contact lenses for managing challenging corneas.

To evaluate the safety and efficacy of new-generation hybrid contact lenses (HCL) among patients with irregular astigmatism. Medical records of 25 patients fit with new-generation HCL (Eyebrid® and AirFlex®) were retrospectively reviewed. The data collected included etiology of irregular astigmatism, uncorrected visual acuity, manifest refraction, spectacle-corrected visual acuity (S-CDVA), steep / flat keratometric values, corneal astigmatism, records of rigid / soft CL fitted before HCL, all parameters of the trial lenses, and the final prescribed HCL parameters and HCL-CDVA. The study included 34 eyes from 25 patients (nine females and 16 males) with an average age of 29 ± 13 (ranging from 8-56) years. In total, 25 eyes with keratoconus, four with post - keratoplasty astigmatism, three with irregular astigmatism due to corneal trauma and two with residual astigmatism after radial keratotomy were fit with HCL. The mean S-CDVA (logMAR) improved significantly from 0.76 ± 0.41 to 0.14 ± 0.15 with HCL (p < 0.01). The most common indication for HCL was inability to fit with rigid gas permeable (RGP) lenses (22 eyes). The average number of lenses to successful fit was 1.4 (mode, 1; median, 1) and ideal fit was achieved with the first trial lens in 25 eyes (73%). Seven patients (nine eyes, 36%) discontinued lens use within the first 6 months because of discomfort (six eyes, 24%), ocular allergy (two eyes, 8%) and tearing of contact lens (one eye, 4%). New-generation HCL may be a suitable option for fitting challenging corneas with irregular astigmatism that cannot be rehabilitated efficiently with rigid lenses.

A physics-based and data-driven hybrid modeling method for accurately simulating complex contact phenomenon

Traditional physics-based contact models have been widely used for describing various contact phenomena such as robotic grasping and assembly. However, difficulties in carrying out contact parameter identification as well as the relatively low measurement accuracy due to complex contact geometry and surface uncertainties are the limiting factors of the physics-based contact modeling methods. In this paper, we present a novel hybrid contact modeling (HCM) method as an endeavor to discover models that can more accurately simulate practical contact scenarios than traditional physics-based contact models. The proposed method is implemented by combining a physics-based contact model and a data-driven error model. This approach is validated by using simulations of a bouncing ball, a flat-shot, and a three-dimensional (3D) peg-in-hole. The results demonstrate the feasibility and consistent performance of the HCM method.

A Hybrid Contact Implementation Framework for Finite Element Analysis and Topology Optimization of Machine Tools

AbstractMachine tool contacts must be represented accurately for reliable prediction of machine behavior. In structural optimization problems, contact constraints are represented as an additional minimization problem based on computational contact mechanics theory. An accurate contact constraint representation is challenging for structural optimization problems: (i) “No penetration” rule dictated by Hertz-Signorini-Moreau (HSM) conditions at contacts is satisfied by varying the contact stiffness during a finite element (FE) solution without control of a user which causes increased contact stiffness “erroneously” to avoid penetration of contacting node pairs in an FE solution; and (ii) the reliability of solutions varies according to the chosen computational contact method. This paper is devoted to the topology optimization of machine tools with contact constraints. A hybrid approach is followed that combines the computational contact problem framework and an obtained stable contact stiffness function (analytically or experimentally). According to the proposed method, the existing optimization problem in FE literature is restated in a reliable form for machine tool applications. To avoid the existing computational challenges and reliability problems, contact forces are directly mapped onto an FE model used in the restated topology optimization problem with the help of proposed method. In this study, the existing and the proposed methods for contact are investigated by means of the solid isotropic material with penalization model (SIMP) algorithm for topology optimization. The effectiveness of the proposed method is demonstrated by comparing the experimental measurements on a prototype machine tool manufactured according to the optimization solutions of the proposed method and those of a conventional machine tool.

A SPH framework for dynamic interaction between soil and rigid body system with hybrid contact method

SummaryA smoothed particle hydrodynamics (SPH) framework for three‐dimensional dynamic soil‐multibody interaction modeling is presented, where both soils and rigid bodies are discretized using SPH particles. In the framework, soils are modeled using the Drucker‐Prager model, while rigid bodies are considered with a multibody dynamics solver. A hybrid contact method suitable for three‐dimensional simulations is developed to model the soil‐body and body‐body frictionless and frictional contacts, where contact forces are calculated based on ideal plastic collision and the unit normal/tangential vectors of the actual surface. Owing to its simplicity in contact detection and accuracy in contact force calculation, the hybrid contact method can be easily incorporated into SPH. Furthermore, graphics processing unit (GPU) parallelization is utilized to improve efficiency. The presented numerical framework and the hybrid contact method are validated using several examples. Numerical results are compared with analytical solutions and results from the literature. Furthermore, two three‐dimensional simulations involving dynamic soil‐multibody interaction are included to demonstrate the application.

Reentrant Kondo effect for a quantum impurity coupled to a metal-semiconductor hybrid contact

Using NRG, we show that a system containing a quantum impurity (QI), strongly coupled to a semiconductor (gap $2 \Delta$) and weakly coupled to a metal, displays a 'reentrant' Kondo stage at low temperatures. The NRG analysis of the corresponding Single Impurity Anderson Model (SIAM) shows that the reentrant stage is characterized by a second sequence of SIAM fixed points: free orbital (FO) > local moment (LM) > strong coupling (SC). In the first stage, the SC fixed point (Kondo temperature $T_{K1}$) is unstable, while the second stage exhibits a much lower Kondo temperature $T_{K2}$, associated to a stable SC fixed point. The results indicate that the reentrant Kondo screening is associated to an effective SIAM, with an effective repulsion $U_{eff}$. This low temperature effective SIAM, which we dub as 'reentrant' SIAM, behaves as a 'replica' of the high temperature (bare) SIAM. The intuitive picture that emerges is that the first Kondo state develops through impurity screening by semiconducting electrons, while the second Kondo state involves screening by metallic electrons, once the semiconducting electrons are out of reach to thermal excitations ($T < \Delta$) and only the metallic spectral weight inside the gap is available for impurity screening. In addition, we analyze a hybrid system formed by a QI `sandwiched' between an armchair graphene nanoribbon (AGNR) and a scanning tunneling microscope (STM) tip, with respective couplings set to reproduce the generic model described above. The energy gap in the AGNR can be externally tuned by an electric-field-induced Rashba spin-orbit interaction. We analyzed this system for realistic parameter values, using NRG, and concluded that the reentrant SIAM, with its associated second stage Kondo, is worthy of experimental investigation.

Hybrid contact lenses for the correction of primary and induced ametropias

The review presents the data on the use of hybrid contact lenses (HCL), a modern method of contact correction of ametropias of diverse origins. A HCL has a central rigid optical zone made of highly gas-permeable material and a flexible peripheral part made of hydrophilic material. These lenses combine the optical effect of gas-permeable corneal lens with the comfort and stable fitting of soft contact lenses. Compared with the corneal (RGP) lenses, HCLs are more comfortable, often are better centrated and more stably fit on the eye. HCLs are successfully used in various refractive disorders: ametropias (with regular cornea), irregular astigmatism, presbyopia, including that combined with astigmatism. This type of lens is a good option of contact correction for patients who have high requirements to the quality of vision.

Correction of Irregular Astigmatism With New-Generation Hybrid Contact Lenses.

To evaluate the safety, efficacy, and on-eye performance of new-generation hybrid contact lenses (HCLs) in visual rehabilitation of eyes with irregular astigmatism and rigid gas-permeable (RGP) contact lens intolerance or failure. The charts of patients who had been fit with new-generation HCLs were retrospectively reviewed. The reason for HCL fit and previous method of correction were noted. After the initial on-eye evaluation, visual and refractive outcomes, slit-lamp biomicroscopy, and lens comfort were evaluated at the last follow-up examination. Forty-seven eyes of 33 patients could be fit successfully with EyeBrid silicone (LCS, Cane, France) or Airflex (SwissLens, Prilly, Switzerland) lenses. The mean number of trial lenses required for ideal fit was 1.4±0.6 (range; 1-3) lenses. The reason for fit was either centration problems with RGP lenses or RGP intolerance. Twenty-nine eyes of 20 patients (72.5%) continued wearing their lenses more than 10 hr a day and for more than 3 months. In these successful wearers, the visual acuity (VA) improved significantly compared with the baseline uncorrected and spectacle-corrected VA (P<0.01), and no serious adverse events were encountered during the mean follow-up period of 10.1±6.4 months. At the last follow-up examination, patients preferred the new-generation HCLs over their habitual correction in regard to both VA and quality (P<0.05). New-generation HCLs seem to provide a viable alternative for visual rehabilitation of irregular astigmatism in selected eyes with RGP intolerance or RGP failure. The ease of the fitting process similar to fitting soft toric lenses and high patient satisfaction seem to be major advantages of these designs.

A new impact dynamics model of a clearance joint considering the adhesive effects in space environment

In space environment, there is severe adhesive effect, and the impact contact process shows different phenomenon due to the adhesive forces. In this paper, a new impact dynamics model of a clearance joint is developed considering the adhesive effects. The Hertz contact model, L-J potential and Dugdale model are combined, and an adhesive force term is included in the original hybrid contact force model. Taking a clearance joint as an example, the theory of adhesive forces during the impact contact process is given, and the influence of the adhesive forces is investigated. Negative forces are discovered at the beginning of the contact, and the contact forces of the modified model are higher than the hybrid model. Besides, the indentation depth is also higher than the hybrid model. The energy conservation principle is employed to explain the phenomena, and the contact forces will be underestimated if the adhesive effects are ignored. This work could be contributed to estimating the contact forces and friction forces more reasonablely in the space environment.

Modeling Planar Joints With Clearance Between the Guide and Roller in Mechanisms

Abstract In mechanisms, the guide and roller form joints with clearance and the roller may make contact with the convex surface or concave surface of the guide. Correctly modeling this type of joint is critical in a mechanism's dynamic performance analysis. This paper proposes a contact kinematic model and a hybrid contact force model for the planar joint and investigates both the convex and concave contact cases. The contact kinematic model is derived from the relative motion between the guide and roller and the hybrid contact force model consists of an elastic force and a damping force. The sliding door mechanism is used as an illustrative example to demonstrate the proposed models. Experimental data are collected for a vehicle's sliding door mechanism. Results show that the proposed models are effective and the simulation results match the general trend of experimental data based on RMS errors.

Modeling and Analysis of Spatial Flexible Mechanical Systems With a Spherical Clearance Joint Based on the LuGre Friction Model

Abstract A computational methodology for modeling spatial flexible mechanical systems with stick-slip friction in a spherical clearance joint is presented. A modified three-dimensional (3D) absolute nodal coordinate formulation based shear deformable beam element with two nodes is proposed and employed to discretize the flexible components. To avoid locking problems, we employed an enhanced continuum mechanics approach to evaluate the beam element elastic forces. The strain components εyz, εyy, and εzz are approximated using linear interpolation to improve the computational efficiency while the loss of accuracy is acceptable. The contact and friction forces in a spherical clearance joint were evaluated by the hybrid contact and LuGre friction models, respectively. Three numerical examples are presented and discussed. A simple pendulum was utilized to prove the correctness of the modified beam element. A classical slider–crank mechanism was employed to validate the computational methodology. A spatial rigid–flexible slider–crank mechanism with a spherical clearance joint was used to investigate the effect of link flexibility and joint clearance on the dynamic behavior of mechanical systems. Using the LuGre friction model, we reproduced the Stribeck effect as it is expected in real world settings. The components with appropriate stiffness play the role of suspension for spatial mechanical systems with imperfect joints. The vibrations of the flexible components play an active role of intensifying the collision in kinematic joint with clearance.