Cantilever Bending Research Articles

Structural design of a polymer matrix composite ship propeller

This work presents the structural design of a propeller, with its profile established using the OpenProp software for a 5 m long competition catamaran at a speed of 5.5 m/s. The materials selected using the Ashby method were polymer matrix composites, and the chosen manufacturing method was vacuum bagging. The determination of the stacking sequence was initially done using panel theory and the macromechanics of composite materials. The stacking sequence was then optimized using the finite element method with Abaqus CAE. Experimental validation was conducted through instrumented cantilever bending tests on both specimens and the blade. The finite element results showed errors of less than 5% compared to the experimental measurements, thus validating the simulations and allowing the blade to be designed with static safety factors greater than eight under operational service conditions.

Characterisation of the Mechanical Properties of Natural Fibre Polypropylene Composites Manufactured with Automated Tape Placement

The integration of natural fibre thermoplastic composites, particularly those combining flax fibres with polypropylene, offers a promising alternative to traditional synthetic composites, emphasising sustainability in composite materials. This study investigates the mechanical properties of flax/polypropylene composites manufactured using flashlamp automated tape placement and press consolidation, individually and in combination. Tensile, compression, three-point bending, and double cantilever beam tests are utilised for comparing these manufacturing processes and the mechanical performance of the resulting composites. The microstructure of the tapes is investigated using cross-sectional microscopy, and the thermophysical behaviour is analysed utilising thermogravimetric analysis and differential scanning calorimetry. The temperature during placement is monitored using an infrared camera, and the pressure is mapped with pressure-sensitive films. The natural fibre tapes show a good aptitude for being manufactured with automated tape placement. The tensile performance of tapes manufactured with automated tape placement is close to that of press consolidated samples. Compression, flexural properties, and the mode I fracture toughness critical energy release rate all benefit from a second consolidation step.

Experimental and numerical study of specific bending behavior of tufted multilayered reinforcements and effects of tufting density

The tufting technology enhances the delamination and impact resistance of composites. The presence of tufting yarns leads to a modification of the structure of the fabric, which affects the bending behavior of tufted reinforcements. Tufted reinforcements experience significant slippage during bending, challenging classical plate and shell theories. Therefore, the bending behavior of tufted reinforcement is investigated and a specific fibrous shell approach is proposed, assuming quasi-inextensibility of fibers and potential slippage between them. The influence of tufting yarns on the bending behavior is integrated into the constitutive model. The experimental results show that the bending stiffness of reinforcements can be increased by tufting density. The simulations exhibit a good agreement with experiments, demonstrating that the proposed approach can accurately capture not only the bending deflections of tufted reinforcements, but also the rotation of material direction indicators. Using the proposed numerical method, the prediction accuracy for deflection and rotation angle of tufted reinforcements reaches 90% in cantilever bending tests and 85% in three-point bending tests. These novel insights can deepen the understanding of the bending behavior of tufted reinforcements and be an asset of the developing numerical model for the forming simulation.

Influence of stacking sequence on flexural properties of hybrid carbon fibre reinforced polymer laminates

This paper presents a numerical investigation of the influence of the stacking sequence and fibre variation of the plies on the flexural properties of carbon fibre-reinforced polymer laminates. The numerical approach utilised a three-point flexural test to evaluate different quasi-isotropic stacking sequences. It also analysed attempts to reinforce failure-prone plies only using a stronger prepreg material to reduce the cost of the laminate. The results were validated by conducting a cantilever bending test and compared with calculations based on classical lamination theory. The beam deflection, normal stress per ply, and the Puck failure criterion inverse reverse factor per ply were used for evaluation and result comparison. The results showed that the quasi-isotropic stacking sequence [0/90/+45/−45]s is the most suitable for beam applications. Replacement of the outer plies of the composite laminate by a stronger ply material made the hybrid laminate performance almost identical to a pure composite laminate consisting of stronger material only.

A stiffness prediction method for variable cross‐section CFRP laminated beam

AbstractTo efficiently design the stiffness of the laminated composite blade‐like structure, an analytical method to assess deformation of variable cross‐section laminated beam under cantilever bending load was developed, in which a local ply density matrix method was introduced to characterize the ply‐up in arbitrary cross‐section after ply drop‐off process and infinitesimal element segment method was used to convert complex variable cross‐section specimen into local equal cross‐section beam structure. The model was validated by the cantilever beam experiment with relative predicted error of stiffness of 5.7%. Inner and outer ply drop‐off models were analyzed using the proposed analytical method. The results show that: (1) stiffness of the outer ply drop‐off model is the highest, at 13.07 N/mm, while that of the inner ply drop‐off model 2 is the lowest, about 17.8% lower than the outer ply drop‐off model; (2) maximum relative deformation difference between the inner ply drop‐off model 2 and outer ply drop‐off model is 21.7% at the free side of the cantilever beam. It indicates that anti‐deformation ability of the variable cross‐section laminated structure can be efficiently designed by the proposed analytical method, especially for the section close to the free side.Highlights Developed a bending stiffness prediction method for composite beam. Variable cross‐section feature of the composite laminate was considered. Local ply density matrix method was introduced to characterize ply drop‐off. Proposed method was validated by cantilever beam bending experiment. Inner and outer ply drop‐off models were compared by the proposed method.

A Multi‐Directional GaN/TiO2 Cuboidal Nanowire Junctionless FET‐Based Ultra‐High Pressure Sensor: A Design Perspective

AbstractIn this work, a nanoelectromechanical system (NEMS) field‐effect transistor (FET)‐based ultra‐high pressure (PR) multi‐directional sensor utilizing a junctionless profile and gate‐all‐around geometry is proposed with the advanced materials GaN/TiO2, named MD‐JLFET PR sensor. A design guide approach is considered, and accurate analysis is conducted starting from the bending of cantilevers based on materials' Young's moduli due to applied pressure and finally extracting the dynamic range of the proposed PR sensor. For the first time, the direction and magnitude of pressure can be measured using gate‐source capacitances (CGS). By employing oxide engineering and fringing field, the sensor achieves distinguishable states compared to previous works. Simulation results demonstrate that the PR sensor can measure pressures ranging from 10 to 30 MPa with high sensitivity in terms of CGS, IOFF, ION, and ION/IOFF. Therefore, the proposed FET‐based PR sensor holds promise for widespread industrial applications requiring ultra‐high pressure range measurement, directional pressure sensing, and high sensitivity.

Measuring fatigue crack growth using microscale specimens: Si-modified Inconel 939 alloy processed by laser powder bed fusion additive manufacturing

Quantitative assessment of fatigue crack growth (FCG) in a Si-modified Inconel 939 alloy, processed by laser powder bed fusion additive manufacturing (L-PBF AM), was conducted through cyclic bending of pre-notched cantilevers with a characteristic cross-sectional dimension of 25 μm × 25 μm. To the best of our knowledge, this work is the first to show that cyclic bending of such pre-notched microscale cantilevers can sense both the threshold regime and the Paris-law regime of FCG quantitatively, despite the small specimen size. The deliberate fabrication of such microscale test specimens enables control of the direction of fatigue crack propagation with respect to a given microstructure, while avoiding the inclusion of volumetric defects within the test volume. Significant differences in FCG behavior were observed when the direction of crack propagation was switched from being parallel to the AM build direction to being perpendicular to it. The present work demonstrates the efficacy of FCG assessment using microscale specimens, which can enhance our understanding of the influence of a given microstructure on crack growth behavior.

Effect of Sextant Fixating Angle of Spiral Clavicle Plate on Biomechanical Stability-A Preliminary Finite Element Study.

A spiral clavicle plate has been accepted for its superior multidirectional compatibility in the treatment of midshaft clavicle fractures from a biomechanical perspective. However, the influence of the sextant angle (spiral level) definition on biomechanical performance has not been clarified. A conceptual finite element analysis was conducted to identify the advantages and drawbacks of spiral clavicle plates with various sextant angle definitions. Conventional superior and three different conceptual spiral plates with sextant angle definitions ranging from 45 to 135 degrees were constructed to restore an OTA 15-B1.3 midshaft clavicle fracture model. Three major loading scenarios (cantilever downward bending, axial compression, and axial torsion) were simulated to evaluate the reconstructed structural stiffness and the stress on the clavicle plate and bone screws. The spiral clavicle plate demonstrated greater capability in resisting cantilever downward bending with an increase in sextant angle and showed comparable structural stiffness and implant stress compared to the superior clavicle plate. However, weakened resistance to axial compression load was noted for the spiral clavicle plate, with lowered stiffness and increased stress on the clavicle plate and screws as the spiral level increased. The spiral clavicle plate has been reported to offer multidirectional compatibility for the treatment of midshaft clavicle fractures, as well as geometric advantages in anatomical matching and reduced skin prominence after surgery. The current study supports that remarkable cantilever bending strength can be achieved with this plate. However, users must consider the potential drawback of lowered axial compression resistance in safety considerations.

A Retrospective Multicentric Study of 52 Nasal and Trans-nasal Implants in 31 Severe Atrophic Patients to Reduce Anterior Cantilever Bending in Full Arch Implant-supported Fixed Rehabilitation.

Severe anterior maxillary atrophy offers few implant-supported rehabilitation solutions to Quad Zygoma characterized by a wide anterior cantilever. One of the possible alternatives to consider before the quad zygoma is the extra-long nasal/trans-nasal implant placement. This retrospective multicentric study shows the predictability of nasal/transnasal implant placement in patients affected by severe anterior maxilla atrophy, with residual anatomical features that indicate this surgery. This specific remote anchorage can often be safely involved in immediate loading with other remote anchorages, such as zygoma and pterygoid implants. In this rehabilitation, it's mandatory to reduce the instability of the frameworks and mechanical stress that could unfavorably affect the implant's prognosis due to the overloading derived from anterior bending. In this retrospective multicentric study, 52 nasal or trans-nasal implants were inserted in 31 atrophic anterior maxillas (Cawood and Howell's class V-VI). All implants were successful after the healing period; even if 27 nasal implants reached an insertional torque equal to or greater than 50 n/cm2, the threshold value estimated to be able to support an immediate load. All 52 implants were successful, so the proportion of success was 100%, with a 97.5% one-sided confidence interval of 88.8-100%. The success rate is achieved only if at least two of the following criteria are met: 1) a greater torque than 50 Ncm as a minimum sufficient condition to plan immediate loading; 2) after a healing period of 16 weeks, the secondary stability is clinically and radiographically evaluated to exclude possible coronal bone resorption: this condition allows the successive prosthetic finalization; 3) the possibility of carrying out a full arch rehabilitation with minimal anterior spread. Insertion torque was <50 Newton centimeters (Ncm) in 14 patients (45%) and 50 Ncm in 17 (55%). Mechanical load was delayed in the former and immediate in the latter. The proportion of torque <50 Ncm was higher in men than in women (69% versus 28%, p=0.033). Immediate torque was not significantly affected by age. Although the sample is not extremely numerically significant, it conveys a clear and significant clinical, surgical indication as never before in the literature; we can state that nasal/trans nasal implants have been very useful in reducing the anterior cantilever and overcoming the anatomical limitations affecting conventional Quad Zygoma.

New Generation Superior Single Plating versus Low-Profile Dual Mini-Fragment Plating of Diaphyseal Clavicle Fractures - A Biomechanical Study

Abstract Background Recently, a new generation of superior clavicle plates was developed featuring the variable-angle locking technology for enhanced screw positioning and optimized plate-to-bone fit design. On the other hand, mini-fragment plates used in dual plating mode have demonstrated promising clinical results. However, these two bone-implant constructs have not been investigated biomechanically in a human cadaveric model. Aims To compare the biomechanical competence of single superior plating using the new generation plate versus dual plating with low-profile mini-fragment plates. Methods Sixteen paired human cadaveric clavicles were assigned pairwise to two groups for instrumentation with either a 2.7 mm Variable Angle Locking Compression Plate placed superiorly (Group 1), or with one 2.5 mm anterior plate combined with one 2.0 mm superior matrix mandible plate (Group 2). An unstable clavicle shaft fracture AO/OTA15.2C was simulated by means of a 5 mm osteotomy gap. All specimens were cyclically tested to failure under craniocaudal cantilever bending, superimposed with bidirectional torsion around the shaft axis and monitored via motion tracking. Results Initial stiffness was significantly higher in Group 2 (9.28±4.40 N/mm) compared to Group 1 (3.68±1.08 N/mm), p=0.003. The amplitudes of interfragmentary motions in terms of craniocaudal and shear displacement, fracture gap opening, and torsion were significantly bigger over the course of 12500 cycles in Group 1 compared to Group 2; p≤0.038. Cycles to 2 mm shear displacement were significantly lower in Group 1 (22792±4346) compared to Group 2 (27437±1877), p=0.047. Conclusion From a biomechanical perspective, low-profile 2.5/2.0 dual plates demonstrated significantly higher initial stiffness, less interfragmentary movements, and higher resistance to failure compared to 2.7 single superior variable-angle locking plates and can therefore be considered as a useful alternative for diaphyseal clavicle fracture fixation especially in unstable fracture configurations.

Biomechanical analysis of plate versus K-wire fixation for metacarpal shaft fractures with wedge-shaped bone defects

BackgroundMetacarpal shaft fracture is a common type of hand fracture. Numerous studies have explored fixing transverse fractures in the midshaft of the metacarpal bone. However, this section of the metacarpal bone is often susceptible to high-energy injury, resulting in comminuted fracture or bone loss. In such cases, wedge-shaped bone defects can develop in the metacarpal shaft, increasing the difficulty of performing fracture fixation. Notably, the research on this type of fracture fixation is limited. This study compared the abilities of four fixation methods to fix metacarpal shaft fractures with wedge-shaped bone defects.MethodsIn total, 28 artificial metacarpal bones were used. To create wedge-shaped bone defects, an electric saw was used to create metacarpal shaft fractures at the midshaft of each bone. The artificial metacarpal bones were then divided into four groups for fixation. The bones in the first group were fixed with a dorsal locked plate (DP group), those in the second group were fixed with a volar locked plate (VP group), and those in the third group were fixed by combining dorsal and volar locked plates (DP + VP group), and those in the fourth group were fixed with two K-wires (2 K group). Cantilever bending tests were conducted using a material testing machine to measure yielding force and stiffness. The four groups’ fixation capabilities were then assessed through analysis of variance and Tukey’s test.ResultsThe DP + VP group (164.1±44.0 N) achieved a significantly higher yielding force relative to the 2 K group (50.7 ± 8.9 N); the DP group (13.6 ± 3.0 N) and VP group (12.3 ± 1.0 N) did not differ significantly in terms of yielding force, with both achieving lower yielding forces relative to the DP + VP group and 2 K group. The DP + VP group (19.8±6.3 N/mm) achieved the highest level of stiffness, and the other three groups did not differ significantly in terms of stiffness (2 K group, 5.4 ± 1.1 N/mm; DP group, 4.0 ± 0.9 N/mm; VP group, 3.9 ± 1.9 N/mm).ConclusionsThe fixation method involving the combined use of dorsal and volar locked plates (DP + VP group) resulted in optimal outcomes with respect to fixing metacarpal shaft fractures with volar wedge bone defects.

Novel, high throughput interface fracture testing method for thermal spray coatings: The modified cantilever bend technique

To measure the interfacial fracture toughness of ceramic/metal interfaces such as thermal spray coatings, a novel modified cantilever beam bending method is proposed. Finite element simulations are used to determine the energy release rate and phase angle for an interfacial crack in a bi-layered cantilever for varying modulus, thickness and beam aspect ratios. A high-throughput experimental procedure for the new test geometry is presented to extract a large number of measurements of interface fracture energy from the same sample, using digital image correlation. Interfacial fracture energies GC, determined using this method are compared for thermal spray coatings of Alumina and YSZ on steel substrates. GC of these coating-substrate combinations follow the same trend as measured from four-point bending or modified clamped beam bend techniques. Advantages and limitations of the technique in comparison to other methods in practice are discussed.

Numerical simulation of bending characteristics of geosynthetic encased stone column

A numerical model of the cantilever bending structure of a geosynthetic encased stone column (GESC) of length 3 m and diameter 0.3 m was established using Z-Soil. The aim was to analyze the stress distribution and bending characteristics of the GESC under a bending load and to investigate the impact of encasement strength, encasement stiffness, gravel friction angle, and diameter on the bending characteristics of the GESC. The maximum bending moment of the GESC under bending conditions occurs at the anchored end. The dividing line of tensile and compressive stresses on the gravel in the anchored end section after bending failure appears at a radius of 0.5 of the column above the section centerline. The geosynthetic sleeve exhibits good resistance to tensile stress. The dividing line between the tensile and compressive stresses is located at the centerline of the section. The mechanical properties of the encasements and gravel has a significant impact on bending characteristics of the GESC. Increasing the strength of the encasement and friction angle of the gravel may significantly improve the bending capacity of the GESC, whereas an increase in the stiffness of encasement and diameter of the column decreases the bending deformation of the GESC.

Axially Non-Uniform Properties Effected Electro-Elastic Fields in Bended Piezoelectric Semiconductor Beams

This paper studied the effects of axially non-uniform material and non-uniform doping on the electro-elastic fields in bent piezoelectric semiconductor beams. The mathematical model is established based on the phenomenological theory of piezoelectric semiconductor and Euler’s beam theory. To solve the governing equations with variable coefficients, the differential quadrature method is adopted. As two representative structures, the pure bending beam and cantilever beam are studied, respectively. From the calculated results, it can be found the varied material properties changed the effective stiffness, as a result, all the field quantities are altered. Meanwhile, the symmetry of all field quantities in a pure bending beam is broken. Considering different Gaussian doping parameters [Formula: see text] and [Formula: see text], it can be observed that the distribution rule of perturbation carrier density becomes complex. The increment of [Formula: see text] broadens the width of optimum range-producing carriers, however, the increment of [Formula: see text] describes the moving of the optimum range from left to right. Importantly, the introduction of non-uniform doping breaks the limitation of perturbation carrier density in a cantilever beam with uniform material properties, the maximum value of perturbation carrier density does not appear at the fixed end only. The obtained results could be the guidance in designing high-performance electric devices.

Concave and convex small radius bending behavior of single and multiple layers reinforcement fabrics

Multilayer reinforcement fabrics are increasingly used for manufacturing structural polymer composites. In liquid molding processes, dry reinforcement fabrics are draped on a mold first, and infused with a liquid resin such as an epoxy in a subsequent manufacturing step. This presents major advantages in terms of operational flexibility and costs. However, draping multilayer reinforcement fabrics on complex mold geometries is challenging. Small radius mold corners constitute a major manufacturing challenge as they lead to variability in dry fabric positioning and resin-rich corners in polymer composite parts. Spring-back of fabrics bent over or into single curvature mold corners is a widespread industrial concern. However, contrary to draping over double-curvature surfaces, bending spring-back from convex or concave single-curvature corners has received very limited attention. No testing method is available. This paper quantifies reinforcement fabric bending spring-back. Single and multiple layer stacks were bent along three directions over convex and into concave 90° corners with five radii spanning 1.59 mm to 12.70 mm. In all cases, five replicated tests enabled variability quantification. Fabric stacks were also quantified using cantilevered bending tests for comparison purposes. Mold radius was found to affect the behavior to a larger extent than testing direction, number of layers or use of a binder.

Highly integrable silicon micropumps using lateral electrostatic bending actuators

We present the design, fabrication, and characterization of an innovative silicon-based micropump with high potential for portable lab-on-chip (LoC) as well as point-of-care (PoC) applications. The actuators of the pump are electrostatic driven in-plane bending devices, which were presented earlier (Borcia et al. in Phys Rev Fluids 3(8): 084202, 2018. 10.1103/PhysRevFluids.3.084202; Uhlig et al. in Micromachines, 9(4), 2018. 10.3390/mi9040190). This paper presents the characterization results achieved with the micropump. The dielectric non-polar liquid Novec7100™ was used as a test liquid due to its adequate physical properties. When applying a periodic voltage of 130 V, a flow rate of up to 80 µL/min was detected. The counter pressure amounts up to 30 kPa and the correspondent fluidic power (volumetric flow rate times the counter pressure) was calculated to 10 µW. The pump contains passive flap valves at the inlet and outlet, which are based on a bending cantilever design. Depending on the application requirements, the micropump can be designed modularly to adjust the specific parameters by an adequate arrangement of pump base units. In this paper, the proof of principle is shown using a single base unit with different number of stacked NED-actuator beams, as well as the serial arrangement of base units. Both modular concepts target the increase of backpressure of the NED-micropump in an inherently different way compared to conventional membrane micropumps.

1072 SIJ Fusion Device Testing

INTRODUCTION: Screw use for SIJ fixation began in the 1980s with the FDA first classifying SIJ fusion devices in 2002. For 40 years, no standardized test method existed. Various methodologies (for bone screw, intramedullary nail, or spinal fusion implants) were modified to accommodate the design and function of sacroiliac devices including ASTM F543’s torsion, pullout, and insertion tests, ASTM F1264’s three- or four-point bending tests, and ASTM F2193’s cantilever bending tests. For many years, SIJ fusion screw indications were limited to fixation of pelvic bones for sacroiliac joint disruptions and degenerative sacroiliitis. While the FDA typically accepted performance testing according to combinations of the aforementioned tests, the specific test expectations have been relatively undefined with inconsistent testing batteries from submission to submission. METHODS: Collaboration among testing experts, manufacturers, and FDA regulators within ASTM’s Spinal Devices sub-committee resulted in the development and publication of ASTM F3574 (Standard Test Methods for Sacroiliac Joint Fusion Devices) based on physiologic loading conditions in the joint as documented in published studies. These tests included: For SI Screws: • Static/dynamic cantilever bending •Static torsion •Driving torque •Pullout For SI Posterior Spacers: •Static/dynamic shear •Static/dynamic torsion. RESULTS: The medical device industry now has access to standardized test methods for SI devices while the FDA or other regulators now have device specific test methods to recommend for pre-clinical testing. CONCLUSIONS: Many new standards drag through years of development and refinement within sub-committees, but ASTM F3574 developed quickly due to efforts of the Spinal sub-committee task group to meet the needs for SI fusion devices.

Behaviour of Grouted Sleeve Wall Connection under Lateral Load

A grouted sleeve’s efficiency in splicing steel bars makes it a potential choice for connecting precast elements. While most studies have focused on the feasibility of grouted sleeves under tension, only a few have investigated the real response of precast concrete members connected using grouted sleeves. In this study, Tapered Head Sleeves (THS) were utilized as connections for precast walls. The objectives were to examine their behavior under incremental lateral loads and assess the feasibility of THS as a wall connection. Five test specimens and one control specimen were fabricated, each comprising two walls joined by THS. The load was applied 1.8 m above the joint until specimen failure. Specimens that experienced bar fracture failure exhibited a relatively large drift upon failure, while those failing due to bar bond slip showed smaller drift. Factors contributing to wall drift included horizontal slip, rocking displacement, cantilever bending deformation, and compressive settlement. The ultimate load increased by 71% as the embedded length increased from 75 mm to 175 mm, and it increased by 50% as the sleeve diameter decreased from 75 mm to 50 mm. The sleeves' performance was evaluated for feasibility based on the strength ratio, drift ratio, ductility ratio, failure mode, performance ratio, serviceability ratio, and length ratio. Only THS-8 met all the criteria, suggesting that the bar's embedded length should be at least 11 times the bar diameter.

Study on the characteristics of increased mechanical stiffness according to changes in LCP shape to reinforce clavicle fractures

The clavicle has various anatomic shapes unique to each individual. Additionally, with the increase in high-energy traumas such as sports injuries and traffic accidents, the patterns of fractures become complex and complicated. Thus, there is a need for a variety of shapes of locking compression plates (LCP) to accommodate different types of fractures and facilitate quicker rehabilitation. The aim of this study is to present different types of LCP that secure fracture fragments and distribute stress evenly, in comparison to typical anatomical LCPs, for reinforcing clavicle fractures. Three models were compared in this study: the typical shape, the center hole removed shape, and the double-curved wing shape. The DICOM (Digital Imaging and Communications in Medicine) file obtained from the computed tomography scan of the patient’s clavicle was used to extract the three-dimensional (3D) clavicle structure. Finite element analysis (FEA) simulation was employed to analyze the structural changes of the LCP under external forces. A reinforced jig was used to apply the same type of external force to each LCP, and an experiment was conducted to analyze the mechanical impact of the LCP’s structural characteristics. When comparing the stress values at the fracture zone point, resulting from the FEA simulation with applied bending forces, it was calculated that the stress dispersion effect was approximately ten times greater when transitioning from a typical LCP shape to a double-curved partial wing structure. Moreover, the ultimate stress increased 3.33 times, from 241.322 to 804.057 N, as the LCP design changed under cantilever bending conditions. This double-curved wing LCP design reduces stress concentration at the fracture site and minimizes stress in the fracture area when subjected to cantilever bending forces. Consequently, this newly designed LCP has the potential to decrease complications related to the plate and accelerate rehabilitation protocols.

Tilt-related alignment issues in miniature micromechanical on-wafer electrical probes composed of multiple flexible microcantilevers

Some new issues concerning the contacting and positioning of small electrical microelectromechanical systems (MEMS) probes based on multiple, flexible microcantilevers are presented here. A tilt error, associated with the lateral probe roll, means that contact touchdown occurs sequentially in different cantilevers upon increasing probe overtravel. To understand the relationship between probe overtravel, tip skate, tip planarity, tip tangency, and contact force in the different contacts, the relationship between mechanical bending and torsion of the flexible cantilevers needs to be accounted for. The study reveals the conditions for achieving contact planarity and desired contact force, as well as the identification of a new ‘differential skate error’ contact misalignment associated with such MEMS probes based on multiple, flexible microcantilevers. This misalignment leads to a ‘differential contact force error’ which has implications for electrical contact quality. An experimental scale model probe based on three cantilevers is used to test the modelling—the results agree well with the predictions of the model. Interestingly, the experiments revealed an effect not accounted for in the modelling; this ‘twist error’ resulted in the cantilever lead edge not being parallel to the touchdown plane. The findings may be useful for engineers involved with the automatic control positioning of such emerging miniature probes, especially in terms of the impact of probe positioning errors.