Long-term Reliability Research Articles

Electrically conductive and highly compressible anisotropic MXene-wood sponges for multifunctional and integrated wearable devices

Although piezoresistive sensors have wide applications in human motion detection and wearable electronics, it is still a challenge to produce multifunctional and integrated sensors with wide working ranges and linear sensing responses. Herein, electrically conductive, highly compressible, and structurally anisotropic MXene-wood (MW) sponges are fabricated by converting balsa wood blocks to compressible wood sponges with extremely low density and highly anisotropic porous structure, followed by decorating with conductive MXene sheets. The MW sponge is utilized to assemble a piezoresistive sensor with a large working range of 0-25 kPa, wide linear sensing ranges of 5%-50% and 0-180o, and excellent long-term reliability under a bending angle of 30° for 5000 cycles. Additionally, the sensor is suitable for monitoring practical human physiological signals including pulse beating, and finger and wrist bending. An all-MW sponge-based multifunctional and integrated sensing system is constructed by integrating the MW sponge piezoresistive sensor, the MW sponge-based solid-state supercapacitor, and the MW sponge electrophysiological electrodes. The sensing system can concurrently detect surface electromyogram and tactile pressures, and hence realize real-time closed-loop controls. The multifunctional and integrated MW sponge sensing system would have great potentials in real-time pressure recognition and human-machine interfaces.

Trap Characterization of Trench-Gate SiC MOSFETs Based on Transient Drain Current

The SiC/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> interface state is one of the main factors that limit the performance and reliability of the SiC metal-oxide-semiconductor field-effect transistor (MOSFET). In this paper, we use a Bayesian deconvolution algorithm to optimize trap feature extraction based on the transient current method and improve the trap extraction accuracy. Using this method, we study the trap capture mechanism in SiC MOSFETs and mainly characterize the trap position, the trap energy level, and the capture time constant. The results obtained show that there are three different types of traps and defects, two of which are SiC interface traps at the gate-source and gate-drain interfaces, with activation energies of 0.089 eV and 0.035 eV, respectively; the third trap type is an oxide trap, and its time constant does not vary with temperature. The characterization results are verified via deep level transient spectroscopy, and the results show reasonable agreement with those obtained by the method proposed in this paper. This method can be combined with electrical stress testing in long-term reliability research to realize nondestructive characterization of the defects of SiC MOSFETs.

Microstructure changes in Sn-Bi solder joints reinforced with Zn@Sn particles in thermal cycling and thermomigration

BackgroundIn the field of electronic packaging, Sn-58Bi solder paste is a promising low-temperature option for step soldering. However, the tendency for the Bi-rich phase to coarsen and segregate poses a significant challenge to the long-term reliability of the solder joints. MethodsThe Sn coated Zn (Zn@Sn) core-shell particles were prepared through a chemical plating process and incorporated into the Sn-58Bi low-temperature solder paste to enhance its reliability. The microstructural and mechanical characteristics of the solder joints were evaluated under thermal cycling and thermomigration conditions to assess their long-term service reliability. Significant findingsThe addition of Zn lowers the nucleation energy and promotes the refinement of the eutectic structure, avoiding a significant reduction in shear strength after thermal cycling. In thermomigration, the heat transfer Q* of Bi is calculated to be 22.5 kJ/mol. The Zn-rich phases hardly move and are evenly distributed within the solder joints, acting like a barrier to prevent the Bi phase diffusing from the hot end to the cold end.

Translational opportunities and challenges of invasive electrodes for neural interfaces.

Invasive brain-machine interfaces can restore motor, sensory and cognitive functions. However, their clinical adoption has been hindered by the surgical risk of implantation and by suboptimal long-term reliability. In this Review, we highlight the opportunities and challenges of invasive technology for clinically relevant electrophysiology. Specifically, we discuss the characteristics of neural probes that are most likely to facilitate the clinical translation of invasive neural interfaces, describe the neural signals that can be acquired or produced by intracranial electrodes, the abiotic and biotic factors that contribute to their failure, and emerging neural-interface architectures.

Probabilistic modeling for long-term fatigue reliability of wind turbines based on Markov model and subset simulation

The success of wind energy, superior to the traditional energy source in sustainability and affordability, is dependent on the reliability of wind turbines. However, to assess the fatigue reliability of wind turbines for long-term operation, massive computational costs are required due to the dynamic response simulations under different environmental scenarios. To reduce the computational cost and to increase the feasibility of long-term fatigue evaluation, a novel probabilistic modeling framework is proposed for long-term fatigue reliability analysis of wind turbines. The proposed framework considers each short-term numerical simulation as a single fatigue event. Thereafter, the long-term sequence of fatigue loading events is determined by the emissions from Markov model which is constrained by environmental conditions. Finally, the statistical information for the sequence of fatigue loading events is obtained so that the counting cycles at each fatigue loading level can be considered a random variable. Therefore, fatigue reliability can be evaluated based on the subset simulation incorporated with the uncertainty of SN curve. The results show that the failure probability can significantly increase as the service lifetime increases without inspections and maintenance. The proposed model, innovatively leveraging the Markov model and subset simulation, is an effective and promising tool for long-term fatigue reliability analysis of wind turbines, as well as any other structures.

Selectively localized growth of two-dimensional perovskites at grain boundaries for efficient and stable CsPbI3 perovskite solar cells

All-inorganic CsPbI3 perovskite solar cells (PSCs) have garnered great interest in the photovoltaic field owing to their high thermal stability and application potential in tandem devices. However, their low operational stability remains a significant issue that limits their practical applications. This study proposes a novel strategy to simultaneously enhance the stability and performance of CsPbI3 PSCs by selectively-localizing growth of two-dimensional (2D) perovskites at grain boundaries. The proposed strategy involves modifying CsPbI3 intermediate films with methylammonium chloride (MACl) and post-treating the CsPbI3 films with phenethylammonium chloride (PEACl). The former induces the formation of δ-phase species at grain boundaries, whereas the latter transforms them into a 2D perovskite in situ. These modifications introduce additional Cl− ions near the CsPbI3 surface, which along with the as-formed 2D perovskite significantly passivate surficial iodine vacancies (IV). This enhances the moisture resistivity of CsPbI3 films, improves the energy level alignment, and promotes carrier transport in PSCs. The optimized CsPbI3 PSC demonstrates a remarkable efficiency of 20.55% and exhibits exceptional long-term storage reliability and operational stability, retaining 95% of the initial efficiency after a 500 h test in ambient air.

Experimental study on the fracture behavior variation of the Au stud bump bonding with different high temperature storage times

PurposeAu stud bump bonding technology is an effective means to realize heterogeneous integration of commercial chips in the 2.5D electronic packaging. The purpose of this paper is to study the long-term reliability of the Au stud bump treated by four different high temperature storage times (200°C for 0, 100, 200 and 300 h).Design/methodology/approachThe bonding strength and the fracture behavior are investigated by chip shear test. The experiment is further studied by microstructural characterization approaches such as scanning electron microscope, energy dispersive spectrometer and so on.FindingsIt is recognized that there were mainly three typical fracture models during the chip shear test among all the Au stud bump samples treated by high temperature storage. For solder bump before aging, the fracture occurred at the interface between the Cu pad and the Au stud bump. As the aging time increased, the fracture mainly occurred inside the Au stud bump at 200°C for 100 and 200 h. When aging time increased to 300 h, it is found that the fracture transferred to the interface between the Au stud bump and the Al Pad.Originality/valueIn addition, the bonding strength also changed with the high temperature storage time increasing. The bonding strength does not change linearly with the high temperature storage time increasing but decreases first and then increases. The investigation shows that the formation of the intermetallic compounds because of the reaction between the Au and Al atoms plays a key role on the bonding strength and fracture behavior variation.

Glaciers Variation at ‘Shocking’ Pace in the Northeastern Margin of Tibetan Plateau from 1957 to 21st Century: A Case Study of Qiyi Glacier

Accelerating glacier shrinkage is one of the most consequential of global warming. Yet, projections for the region remain ambiguous because of the tremendous spatial heterogeneity, especially in the Qilian Mountains, where glacier melt runoff is a vital water resource for the arid downstream area. To better understand glacier changes in this region, this study took regional representative Qiyi Glacier as an example and applied an enhanced distributed surface mass balance (SMB) model to glimpse the SMB variation and possible impacts on melt runoff under the RCP 4.5 and RCP 8.5 scenarios. Further, we combined a modified volume-scaling method to update the glacier geometry gradually to enhance long-term reliability. When forced with observed daily temperature and precipitation, the reconstructed glacier SMB, from 1957 through 2013, agrees well with the in situ observations. The result indicates an abrupt change for SMB from positive to negative in 1992 and subsequent mass accelerated loss after 2000. The increased summer air temperature and the pattern of large-scale atmospheric circulation shifts might both cause these changes. Using projected climate forcing from as many as 31 coupled GCMs from the CMIP 5 ensemble, the Qiyi Glacier is projected to undergo sustained SMB loss throughout the 21st century for both RCPs. By 2100, the Qiyi Glacier will lose ~25 m water equivalent (w.e.) for RCP 4.5 and ~37 m w.e. for RCP 8.5. Whereas the glacier area will shrink by 43% for RCP 4.5 and 54% for RCP 8.5 relative to 2013 glacier content, corresponding to the volume of the Qiyi Glacier will lose by 54% for RCP 4.5 and by 65% for RCP 8.5, accordingly. Simultaneously, the glacier terminus will experience extreme melts. The terminus elevation of the Qiyi Glacier will retreat from 4310 m a.s.l. in 2013 to 4810 m a.s.l. (RCP 4.5) and 4838 m a.s.l. (RCP 8.5) by the end of 2100, which will exceed the multi-year average ELA (4749 m) from 1957 to 2013. If the warming trends keep and glaciers melt like the Qiyi Glacier with this ‘shocking’ rate, it will raise the possibility of crippling, long-term water shortages for Hexi corridors.

Effect of interfacial structure on peel strength between Cu and AlN bonded with a Mg–Ti co-deposited film

Eliminating electrochemical migration of Ag is effective for improving the long-term reliability of power modules for high-voltage applications. In this work, a Cu plate was bonded onto an AlN substrate via Mg–Ti co-deposited films with three different compositions as Ag-free bonding materials between 800 and 950 °C for 0.5 h. The interfacial structures and the peel strength between the Cu and AlN were investigated by using the Surface And Interfacial Cutting Analysis System (SAICAS). Cu was bonded onto AlN through a TiN layer consisting of TiN particles and a Cu-containing grain boundary phase. All fractures at the Cu/AlN interface were observed to occur between the TiN layer and AlN after the SAICAS test. The peel strength at the Cu/AlN interface, which was independent of the thickness of the TiN layer, increased exponentially with increasing bonding temperature. Cu-containing phases, such as grain boundary phases and segregation phases between TiN particles and AlN, were present at the TiN layer/AlN interface. Mg and O were segregated at the interface, which had a high peel strength between the Cu-containing phase and AlN, while at the signal peak position of Mg, a plateau was observed in the Al concentration distribution between the Cu-containing phase and TiN particle. The peel strength of the Cu-containing phase/AlN interface, which increased as the O concentration in the Mg-containing segregation layer increased, dominated that of the TiN layer/AlN interface.

Excellent high-temperature dielectric energy storage of flexible all-organic polyetherimide/poly(arylene ether urea) polymer blend films

Current commercial dielectric polymers can scarcely meet the increasing demand for advanced capacitors under harsh thermal conditions up to 150 °C due to the severely degraded efficiency at high electric field and high temperature. Here, we design and prepare all-organic polyetherimide/poly(arylene ether urea) polymer blend films which exhibit a record-high discharged energy density of ∼4.84 J/cm3 with an efficiency higher than 90% at 150 °C among the reported free-standing all-organic polymer-based dielectrics. Moreover, the capacitive energy storage performance shows an excellent temperature stability from room temperature to 150 °C, and a great long-term reliability over 20,000 cycles is achieved under working conditions of 200 MV/m and 150 °C in hybrid vehicles. These excellent dielectric energy storage performances benefit from the introduction of molecular trapping centers which notably reduce the high-temperature conduction loss. Our research provides a convenient and effective method to develop high-temperature polymer dielectrics.

Highly integrated, breathable, metalized phase change fibrous membranes based on hierarchical coaxial fiber structure for multimodal personal thermal management

The development of personal thermal management textile is of great significance to satisfy the individual thermal comfort in an energy saving manner. However, major challenges remain, such as the sacrificed permeability, and limited mechanical durability, hindering long-term wearing comfort and reliability. Herein, a breathable, integrated thermoregulating fibrous membrane combining photo/electrothermal conversion and energy storage/release performance was fabricated for all-weather, on-demand, personal thermal management. We have delicately constructed a hierarchically ordered coaxial fiber structure that assembled functional components together for a versatile platform, through facile coaxial electrospinning followed by polydopamine (PDA) assisted metal deposition techniques. Interestingly, the intermediate PDA layer not only favors homogeneous loading of Ag nanoparticles (AgNPs), but also facilitates the interfacial bonding of the adjacent metal layer and the phase change fiber substrate for a seamlessly integrated system with improved structural stability and robust electrical performance. As a result, benefiting from the hierarchical coaxial structure of individual fibers and the overall well-preserved porous structure, we have fabricated an highly integrated, breathable, metalized phase change fibrous membrane with admirable heat enthalpy of 101.1 J/g, decent solar heating capability (up to 63.2 °C at 100 mW/cm2), and low voltage-driven Joule heating performance (up to 76.8 °C at 3.5 V), which exhibited a broad application prospect in next-generation wearable personal thermal management.

A STRUCTURED RELIABILITY AND MAINTAINABILITY ASSESSMENT MODEL: AN APPLICATION TO HIGH VOLTAGE MOTORS

Motors are one of the vital equipment and generally the higher in numbers in oil and gas processing facilities. The primary function is to drive the process equipment such as compressors, fans, pumps etc. Unreliability of the motors is a threat to safety but also to production loss and high operating expenditure. Motors experience higher failure rates and maintenance costs with age due to lower focus during useful life periods. In order to properly address the long-term reliability and maintainability of the motors and associated subsystems, this paper aims to propose a structured methodology and set of tools to ensure effective assessment. The proposed model mainly consists of data collection, analysis, assessment, financial analysis and later developed actions to properly address the concerns. Equipment failure and repair data is a challenge to any reliability assessment; hence, proposed methodology was introduced to collect, verify and validate the data. Later, multiple tools such as Pareto Analysis, Failure Mode and Effect Analysis and Root Cause Analysis were used to perform a detailed assessment. Weibull analysis was also explored to understand the failure modes, which ultimately helped in improving the availability of the motors. The proposed methodology has been applied to high-voltage motors to observe the effectiveness of the tools and proposed model in addressing reliability and maintainability. The results show significant reliability improvements of 12% (from 58% to 70%) and prove that the structured method can be effectively used in complex process facilities with significant benefits.

Performance Assessment of Three-Phase NPC-Based Grid Integrated Single-Stage Solar PV System With Reduced DC Bus Capacitor

This work proposes an effective reduction in the capacitor size of the DC-bus of a conventional three-phase neutral point clamped (NPC) inverter-based grid integrated single-stage solar photovoltaic (PV) system. This has been done by implementing a metallized polypropylene film DC-bus capacitor instead of an electrolytic capacitor. As an outcome, this enhances the system&#x0027;s long-term reliability, reduces cost, and increases the system's life expectancy. The unbalance in capacitor voltage due to a small DC-bus capacitor is also identified. As a solution, a carrier-based modified modulation strategy is implemented to improve the dynamic response of neutral-point voltage. A single-stage solar PV array is utilized in this paper. An optimal power extraction (OPE) scheme is adopted to extract solar PV power. The DC-bus voltage overshoot issue that arises during the change in irradiation is resolved, and minimal oscillations are observed. The implemented scheme allows the feeding of the extracted power to the three-phase grid via the NPC converter, which in turn diminishes the total harmonic distortion (THD) of the grid. The PI controller minimizes the voltage and current error. The system performance is observed using a MATLAB version simulation model and authenticated through the experimental results obtained from the laboratory prototype.

Insight on PV parameters on CIGS solar cell under different grading profiles

Photovoltaic (PV) technology has received a lot of attention internationally since it is considered to be the most economical approach to satisfy the world's increasing energy demands. Copper indium gallium selenide (CIGS) solar cell has higher absorption coefficient, long-term reliability, and low construction cost. CIGS material has a tunable bandgap that can be adjustable. In this article, study on CIGS solar cells has been performed, and strategies were proposed for maximizingefficiency using “grading”. SCAPS-1D tool has been used for numerical simulation. CIGS solar cell performance is investigated with graded profiles i.e., exponential function, beta function, power law and without a graded profile (uniform pure CIGS). The results show that cells performance appears to be significantly impacted by grading. Graded power law of CIGS solar cell has delivered power conversion efficiency (PCE) of 23.8%, however the efficiency achieved by ungraded CIGS solar cells is 17.8%. As a result, the observations given in this paper may stimulate greater interest in the topic among researchers who study in the field, motivating them to design this structure as well as investigate further possibilities for improving its effectiveness.

Long-term consistency of clinical sensory testing measures for pain assessment.

Understanding the stability of quantitative sensory tests (QSTs) over time is important to aid clinicians in selecting a battery of tests for assessing and monitoring patients. This study evaluated the short- and long-term reliability of selected QSTs. Twenty healthy women participated in three experimental sessions: Baseline, 2 weeks, and 6 months. Measurements included pressure pain thresholds (PPT) in the neck, upper back, and leg; Pressure-cuff pain tolerance around the upper-arm; conditioned pain modulation during a pressure-cuff stimulus; and referred pain following a suprathreshold pressure stimulation. Intraclass correlation coefficients (ICC) and minimum detectable change (MDC) were calculated. Reliability for PPT was excellent for all sites at 2 weeks (ICC, 0.96-0.99; MDC, 22-55 kPa) and from good to excellent at 6 months (ICC, 0.88-0.95; MDC, 47-91 kPa). ICC for pressure-cuff pain tolerance indicated excellent reliability at both times (0.91-0.97). For conditioned pain modulation, reliability was moderate for all sites at 2 weeks (ICC, 0.57-0.74; MDC, 24%-35%), while it was moderate at the neck (ICC, 0.54; MDC, 27%) and poor at the upper back and leg at 6 months. ICC for referred pain areas was excellent at 2 weeks (0.90) and good at 6 months (0.86). PPT, pressure pain tolerance, and pressure-induced referred pain should be considered reliable procedures to assess the pain-sensory profile over time. In contrast, conditioned pain modulation was shown to be unstable. Future studies prospectively analyzing the pain-sensory profile will be able to better calculate appropriate sample sizes.

Development and demonstration of concentric-type HTS power cable for distribution grid in Shenzhen urban

High-temperature superconducting (HTS) cable can transmit massive power with little dissipation in a limited corridor, which is an attractive solution for future power transmission. Shenzhen Power Supply energized a 400 m/10 kV/2.5 kA concentric HTS cable system on 28 September 2021 to power Ping’an Financial Centre, a Shenzhen’s landmark building, which was the debut of concentric HTS cable made of YBCO in the urban area of a megacity. For more than 1 year, the HTS cable system has been operating well and will continue to operate for a long time. This paper systematically reviews the system specification, cable and its accessories design, cryogenic cooling system design, type and exploratory test, project construction, pre-commissioning test, and operation of the demonstration cable system. Based on our R&amp;amp;D practice, we identify that cost, long-term reliability, and operational simplicity are the main hinders factors that need to be addressed to advance the large-scale application and we propose a set of solution ideas meanwhile.

Design and performance of a 3D-Printed magnetorheological fluid-based adaptive vibration isolator

Emerging additive manufacturing (or 3D printing) can be advantageous for developing magnetorheological fluid (MRF)-based vibration isolators (MRVIs) because their designs can be easily and efficiently customized and also in-situ fabrication and repairing can be possible. In this study, a simple and compact adaptive MRVI was fabricated by using a 3D printing method. A masked stereolithography (MSLA) 3D printer was used for the fabrication of the rubber bellow and plastic lid parts of the MRVI. The electromagnet was mounted onto the lid, the reservoir was filled with an MRF, and the lid was simply assembled with the reservoir using a 3D-printed large thread without traditionally machined components. Using a material testing machine, the damper forces of the 3D-printed MRVI were measured under a constant velocity loading condition for different magnetic fields. From these tests, the magnetic field-controllable performances of the MRVI such as the MR yield force, the dynamic force range, the dissipated energy, and the secant stiffness were obtained. For the evaluation of the long-term performance reliability of the MRVI due to the MRF sedimentation, its magnetic field-controllable performances were tracked for 156 days with the variable testing intervals. Finally, the feasibility of the 3D-printed MRVI was experimentally confirmed.

Integrated silicon photonic MEMS

Silicon photonics has emerged as a mature technology that is expected to play a key role in critical emerging applications, including very high data rate optical communications, distance sensing for autonomous vehicles, photonic-accelerated computing, and quantum information processing. The success of silicon photonics has been enabled by the unique combination of performance, high yield, and high-volume capacity that can only be achieved by standardizing manufacturing technology. Today, standardized silicon photonics technology platforms implemented by foundries provide access to optimized library components, including low-loss optical routing, fast modulation, continuous tuning, high-speed germanium photodiodes, and high-efficiency optical and electrical interfaces. However, silicon’s relatively weak electro-optic effects result in modulators with a significant footprint and thermo-optic tuning devices that require high power consumption, which are substantial impediments for very large-scale integration in silicon photonics. Microelectromechanical systems (MEMS) technology can enhance silicon photonics with building blocks that are compact, low-loss, broadband, fast and require very low power consumption. Here, we introduce a silicon photonic MEMS platform consisting of high-performance nano-opto-electromechanical devices fully integrated alongside standard silicon photonics foundry components, with wafer-level sealing for long-term reliability, flip-chip bonding to redistribution interposers, and fibre-array attachment for high port count optical and electrical interfacing. Our experimental demonstration of fundamental silicon photonic MEMS circuit elements, including power couplers, phase shifters and wavelength-division multiplexing devices using standardized technology lifts previous impediments to enable scaling to very large photonic integrated circuits for applications in telecommunications, neuromorphic computing, sensing, programmable photonics, and quantum computing.

2D characterisation and evaluation of multi-material structures towards 3D hybrid printing

ABSTRACT Multi-material manufacturing through the hybridisation of printed electronics and additive manufacturing has gained great interest recently. However, such hybridisation attempts are not trivial due to the need for functional material development and compatible process identification, as well as further performance understanding, comprehensive characterisation and long-term reliability evaluation of multi-material parts. While some multi-material structures from functional materials such as silver inks have been demonstrated via the integration of direct writing systems into stereolithography or material extrusion platforms, the performance assessment and characterisation of parts manufactured using such integrated systems is still required. Therefore, this research presents a comprehensive assessment of multi-material structures manufactured using syringe deposition and material extrusion platforms. Test specimens were subjected to various characterisation activities such as thickness measurement, resistance measurement, roughness tests, wettability measurement, adhesion tests, and morphological analysis. Results and statistical analyses suggested that the dry thickness and conductivity of deposited films were dependent on the substrate material. Adhesion between the conductive film and substrate was affected by both substrate material and ink deposition angle. Also, the interaction of conductive films with polycarbonate substrate was found to be noticeably better among all substrates due to low resistivity and enhanced adhesion at low thicknesses.

Validity and reliability of the assessment of hand flexors stiffness using a new electromechanical oscillatory device in people with stroke.

Hyper-resistance after a central nervous system injury has been largely referred to as spasticity, which is but one of its neural components. Assessment largely relies on clinical scales (Modified Ashworth scale - MAS and Modified Tardieu scale, MTS) which are unable to distinguish between the non-neural (tissue-related) and the neural (central nervous system-related) components. This study assessed criterion validity and reliability (reproducibility) of muscle stiffness measures, namely, maximum elastic stiffness (ELmax), viscous stiffness (VI), and path length (L-path) in the hand flexor muscles among people with stroke. Measurements were obtained with a wrist-electromechanical oscillatory device (w-EOD). Twenty-four people with arm impairment after stroke were evaluated with the w-EOD and clinical assessment (MAS and MTS), twice on the same day (short-term reliability) and once 10 days later (long-term reliability). For criterion validity, a Spearman coefficient ( r ) was calculated between stiffness values and the clinical scales. For reliability, intraclass correlation coefficients (ICCs), SEM, and MDC95 were calculated. Moderate correlations were observed between EL max and MAS ( r = 0.49) and MTS (V2, r = 0.43; V3, r = 0.49) of the wrist flexors, and finger flexors (MAS, r = 0.60; MTS V2, r = 0.56; MTS V3, r = 0.55). There was a poor correlation between the clinical scales and VI and L-path. Reliability was excellent for all stiffness measurements at short term (EL max : 0.95, VI: 0.94, L-path: 0.92) and good at long term (EL max : 0.87, VI: 0.76, L-path: 0.82). In conclusion, stiffness measurements are valid and reliable to evaluate hyper-resistance in people with stroke.