Rotational Displacement Research Articles

Evaluation of a Locking Autocompression Screw Model in Pauwels Type-3 Femoral Neck Fracture: In Vitro Analysis.

Femoral neck fractures in young adults are uncommon, resulting from high-energy trauma. Despite their infrequency in this population, there is higher rate of complications, especially in the more vertical fracture line, classified by Pauwels as a type-3 femoral neck fracture. The implant type is of paramount importance for maintaining anatomical reduction, since it must resist the deforming forces that act on the fracture. We comparatively evaluated two constructions of the novel locking autocompression implant (X-PIN and X-PIN+P) using the finite element method and previously established methods for treating Pauwels type-3 femoral neck fractures. Six fixation models were developed for the study: a dynamic hip screw (DHS), a DHS with an anti-rotation screw (DHS+P), the inverted triangle multiple cannulated screws construction (ASNIS), the multiple cannulated screws in an L-configuration (L), and the two models of the novel locking autocompression screw (X-PIN and X-PIN+P). Under the same conditions with a load of 2100 N, the following parameters were evaluated using SIMLAB® software: the main maximum (Max P), main minimum (Min P), localized maximum P1 (Max P1), localized maximum P2 (Max P2), total displacement, localized displacement, rotation displacement, and von Mises stress. Compared to the DHS+P and ASNIS models, the X-PIN+P model presented, respectively, increases of 51.6% and 64.7% for Max P, 85% and 247% for Min P, and 18.9% and 166.7% for von Mises stress. Max P1 did not differ between the models, but Max P2 was 55% and 50% lower for X-PIN+P than ASNIS and L, respectively. All displacement values were lower for X-PIN+P than the other models. In this FEM testing, the X-PIN+P was superior to the other models, which was due to improvement in all parameters of stress distribution, displacement, and von Mises stress compared to models using a lateral plate (DHS and DHS+P) or not (ASNIS and L).

A novel plastic failure model of prestressed anchor cables for upper bound stability analyses of rotational reinforced slopes

In the existing upper bound limit analyses (UBLA) of rotational slopes reinforced with prestressed anchor cables, the mobilized axial forces of all cables are assumed to be equal to the ultimate pullout force. However, such an assumption overestimates the mechanical contribution of prestressed anchor cables, resulting in excessively high safety factors. In this technical note, we aim to tackle this issue by proposing a pseudo-plastic design concept, in which soil masses and prestressed cables are treated as plastic and elastic-plastic, respectively, when slopes collapse. A pseudo-plastic failure model of prestressed anchor cables is proposed, where the variation of tension forces and movement of anchor heads are accounted for. Several interesting conclusions are drawn as follows: (1) Contrary to the conventional plastic failure mode of cables, upper bound solutions obtained by the proposed model are much closer to the exact solutions. (2) Variation of factors of safety (FSs) against the accumulated rotational displacement can be explained by the force-displacement curve obtained in the pullout test of prestressed anchor cables. (3) The sliding slope reinforced with cables may turn out to be stable after a slight rotational movement, which can be utilized in the economical design.

Simultaneous Measurement of Patellofemoral Joint Kinematics and Contact Mechanics in Intact Knees: A Cadaveric Study.

ObjectivePatellofemoral kinematics and contact mechanics are important measurements for the assessment of patellofemoral joint (PFJ) problems. Simultaneously measuring PFJ contact pressures and kinematics is a challenging task. The purpose of this study was to simultaneously measure the kinematics and mean/peak contact pressures in the PFJs of cadaveric knees.MethodsThis was a comparative study performed on fresh cadaveric knees. The kinematic data was acquired for nine cadaveric knees using an optical tracking system. Data about the contact pressure and contact area in the PFJ was obtained at knee flexion angles of 0°, 30°, 60°, 90°, and 120° using a pressure sensor. Intraclass correlation coefficients (ICCs) and minimal detectable differences (MDDs) of six degrees of freedom (6 DOF) in the PFJs were calculated. ICCs and the MDDs of contact pressure, peak pressure, and contact area in the PFJs were also analyzed. We also compared the kinematics of the cadaveric knees before and after the insertion of the pressure sensor.ResultsAll ICC values of 6 DOF in the PFJs were found to be greater than or equal to 0.924. Regarding medial–lateral rotation, the patellar showed a simplified movement pattern that demonstrated progressive lateral rotation of 4.8° ± 3.4° at 120° of knee flexion. While for patellar tilting, the patella showed medial tilting that peaked at 7.2 ± 2.5° at 30° of knee flexion. Whereas no significant differences in PFJ kinematics were found between with and without the placement of the pressure sensor at all knee flexions (P > 0.05). Most of the ICC values for contact pressure, peak contact pressure, and contact area ranged from 0.8 to 0.9. The MDDs for rotational displacement were 0.9° and 0.6 mm for translational displacement. No statistical differences in patellar kinematics were found before and after the insertion of the pressure sensor.ConclusionsThe setup in the present study enables researchers to simultaneously and synchronously collect real‐time PFJ kinematics and tibiofemoral joint (TFJ) biomechanical kinematic data with high reliability. The low MDDs enabled the researchers to obtain an accurate interpretation of the kinematic and contact mechanics measurement using the experimental setting used in the present study.

Insights into Cation Ordering of Double Perovskite Oxides from Machine Learning and Causal Relations

This work investigates the origins of cation ordering of double perovskites using first-principles theory computations combined with machine learning (ML) and causal relations. We have considered various oxidation states of A, A', B, and B' from the family of transition metal ions to construct a diverse compositional space. A conventional framework employing traditional ML classification algorithms such as Random Forest (RF) coupled with appropriate features including geometry-driven and key structural modes leads to highly accurate prediction (~98%) of A-site cation ordering. We have evaluated the accuracy of ML models by entailing analyses of decision paths, assignments of probabilistic confidence bound, and finally introducing a direct non-Gaussian acyclic structural equation model to investigate causality. Our study suggests that the structural modes are the most important features for classifying layered, columnar and rock-salt ordering. For clear layered ordering, the charge difference between the A and A' is the most important feature which in turn depends on the B, B' charge separation. Based on the outputs from ML models, we have designed functional forms with these features to derive energy differences forming clear layered ordering. The trilinear coupling between tilt, rotation, and A-site antiferroelectric displacement in Landau free-energy expansion becomes the necessary condition behind the formation of A-site cation ordering.

Three-Degree-of-Freedom Electromagnetic Microactuator With Powder-Based Sm-Fe-N Magnets and Parylene Beams

In this paper, we report a moving magnet type electromagnetic actuator with three-degree-of-freedom, namely the displacement in XY axes and rotation around Z axis, by utilizing rare earth magnetic powder Sm-Fe-N. Parylene was utilized to fabricate springs to suspend four drive units and a center moving stage located in the four corners and the center of the actuator, respectively. The rare earth magnetic powder Sm-Fe-N with wax were embedded in the silicon frames of the drive units with a parylene layer, followed by magnetization by an 8 T pulse magnetic field to obtain permanent micromagnets. The motion of the center moving stage can be controlled by the drive units. To obtain an in-plane displacement in the XY axes, compensation coils were fabricated in a print circuit board (PCB) to eliminate the Lorentz force in the Z axis. The application of a direct current (DC) allowed the center moving stage to move in the XY axes by 55 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> and rotate almost 3 degrees around the Z axis, respectively. The resonance frequencies of the motion in the XY axes and the rotation around the Z axis were 630 Hz and 675 Hz, respectively.

Visual Odometry with an Event Camera Using Continuous Ray Warping and Volumetric Contrast Maximization.

We present a new solution to tracking and mapping with an event camera. The motion of the camera contains both rotation and translation displacements in the plane, and the displacements happen in an arbitrarily structured environment. As a result, the image matching may no longer be represented by a low-dimensional homographic warping, thus complicating an application of the commonly used Image of Warped Events (IWE). We introduce a new solution to this problem by performing contrast maximization in 3D. The 3D location of the rays cast for each event is smoothly varied as a function of a continuous-time motion parametrization, and the optimal parameters are found by maximizing the contrast in a volumetric ray density field. Our method thus performs joint optimization over motion and structure. The practical validity of our approach is supported by an application to AGV motion estimation and 3D reconstruction with a single vehicle-mounted event camera. The method approaches the performance obtained with regular cameras and eventually outperforms in challenging visual conditions.

Enhancing Mixing Performance in a Rotating Disk Mixing Chamber: A Quantitative Investigation of the Effect of Euler and Coriolis Forces.

Lab-on-a-CD (LOCD) is gaining importance as a diagnostic platform due to being low-cost, easy-to-use, and portable. During LOCD usage, mixing and reaction are two processes that play an essential role in biochemical applications such as point-of-care diagnosis. In this paper, we numerically and experimentally investigate the effects of the Coriolis and Euler forces in the mixing chamber during the acceleration and deceleration of a rotating disk. The mixing performance is investigated under various conditions that have not been reported, such as rotational condition, chamber aspect ratio at a constant volume, and obstacle arrangement in the chamber. During disk acceleration and deceleration, the Euler force difference in the radial direction causes rotating flows, while the Coriolis force induces perpendicular vortices. Increasing the maximum rotational velocity improves the maximum rotational displacement, resulting in better mixing performance. A longer rotational period increases the interfacial area between solutions and enhances mixing. Mixing performance also improves when there is a substantial difference between Euler forces at the inner and outer radii. Furthermore, adding obstacles in the angular direction also passively promotes or inhibits mixing by configuration. This quantitative investigation provides valuable information for designing and developing high throughput and multiplexed point-of-care LOCDs.

Virtual Reality for Shoulder Rehabilitation: Accuracy Evaluation of Oculus Quest 2.

Virtual reality (VR) systems are becoming increasingly attractive as joint kinematics monitoring systems during rehabilitation. This study aimed to evaluate the accuracy of the Oculus Quest 2 in measuring translational and rotational displacements. As the Oculus Quest 2 was chosen for future applications in shoulder rehabilitation, the translation range (minimum: ~200 mm, maximum: ~700 mm) corresponded to the forearm length of the 5th percentile female and the upper limb length of the 95th percentile male. The controller was moved on two structures designed to allow different translational displacements and rotations in the range 0–180°, to cover the range of motion of the upper limb. The controller measures were compared with those of a Qualisys optical capture system. The results showed a mean absolute error of 13.52 ± 6.57 mm at a distance of 500 mm from the head-mounted display along the x-direction. The maximum mean absolute error for rotational displacements was found to be 1.11 ± 0.37° for a rotation of 40° around the z-axis. Oculus Quest 2 is a promising VR tool for monitoring shoulder kinematics during rehabilitation. The inside-out movement tracking makes Oculus Quest 2 a viable alternative to traditional motion analysis systems.

Comparison of short-term condylar positional changes in mandibular prognathism after surgery-first approach: Symmetric setback versus asymmetric setback

The aim of this study was to compare how the displacement of the mandibular condyle changed after symmetric or asymmetric mandibular setback surgery using the surgery-first approach (SFA). Patients who underwent mandibular setback surgery using the SFA were selected and divided into a symmetry group (n = 18) with differences of less than 2 mm between the right and left setback, and an asymmetry group (n = 18) with a difference of greater than 2 mm. Cone-beam computed tomography (CBCT)-generated cephalograms were obtained after three-dimensional superimposition of CBCT images taken before surgery (T0), within one week after surgery (T1), and seven months after surgery (T2). The condylar positions were measured. Condylar positional changes according to time were compared between the two groups and correlation analysis was performed. There were significant positional changes in mandibular condyles over time in both groups. However, most of these changes returned to their initial state. In the asymmetry group, there was a greater internal rotation of the mandibular condyle on the lesser setback side. The correlation analysis results revealed that only the setback difference was associated with rotational displacement of the condyle on the lesser setback side at two time points (T1-T0, T2-T0). In the SFA, significant condylar displacement occurred immediately after both symmetric and asymmetric mandibular setback surgery, and the right/left difference in mandibular setback showed a significant positive correlation with rotational displacement. Although more significant rotational displacement of the mandibular condyle was observed after asymmetric mandibular setback surgery, the amount was not large enough to be clinically significant.

Identification of crack by vibration analysis and restoration of dynamic response in beams using PZT sensor/actuator

ABSTRACT The endeavour of this research is to locate the position of small-depth cracks in beam type structural element and to restore the dynamic response of the cracked beam through steady-state vibration analysis with the help of piezoelectric material. An open crack induces a discontinuity in rotational displacement curve of a vibrating element, though this discontinuity is an efficient parameter to detect the crack, but at the same time, there is no proper conventional method to check the discontinuity in a vibrating beam. The present study reveals that a bending piezoelectric sensor can efficiently detect the discontinuity due to the fact that the voltage output from the piezoelectric sensor depends on the difference in rotational displacement at its two ends. Subsequently, it is observed that by applying external time-varying voltage on a piezoelectric patch, the dynamic response of a cracked beam can be restored. Since the applied external voltage on the patch produces a local moment near the crack which diminish the effect of crack. Mathematical and finite element model are developedto obtain the results. An experimental set-up is made to validate few of the theoretically obtained results.

Enhanced strain of (Ba, Ca)(Ti, Zr, Sn)O3 ferroelectrics with multiphase polar nanoregions coexistence and BO6 octahedral rotation

The cation displacement closely related to the local symmetry and corner-connected oxygen octahedral rotation are the structural origin of macroscopic properties in ABO3 perovskite oxides. This work describes in detail the relationship between microstructure and macroscopic properties in 0.78BT-0.12CT-0.1BZS ceramic, which achieves the enhanced strain of 0.19 % with a hysteresis of 6.56 %. The atomic level structure is revealed by aberration corrected scanning transmission electron microscope (AC-STEM). The AC-STEM HAADF images reveal the coexisting of polar nanoregions with O and T symmetries. Such a microstructure has a lower energy barrier, facilitating dynamic polarization rotation flexibly under external stimuli. The AC-STEM ABF image reveals the existence of the BO6 octahedral rotation, with rotation patterns of the a0b0c0 and a-b+c-, and rotation angles are quantitatively measured. The BO6 octahedral rotation and cation displacement are found to be consistent, the greater octahedral rotation with greater cation displacements. These results have important implications for understanding the structural origin of the excellent properties in ferroelectrics.

Comparative finite element analysis of four different internal fixation implants for Pauwels type III femoral neck fractures in various fracture angles in the sagittal plane.

Objectives This study aimed to evaluate the performance of four different fixation techniques for Pauwels type III femoral neck fractures considering the fracture morphology in the sagittal plane.Materials and methods We constructed three different fracture morphologies in the sagittal plane in Pauwels type III femoral neck fractures: posteriorly angled at 20°, neutral, and anteriorly angled at 20°. We set up four fixation devices, including three cannulated screws (3CS), a dynamic hip screw with an antirotational screw (DHS+CS), a proximal femoral locking plate (PFLP), and three cannulated screws with a medial buttress plate (3CS+MBP). The twelve models were created and analyzed using the finite element analysis.Results The finite element analysis revealed that 3CS+MBP yields better results in total vertical and rotational displacements, regardless of the fracture angle in the sagittal plane. For the anterior and posterior angled fractures in the sagittal plane, the PFLP was superior to the DHS+CS. However, the DHS+CS exhibited less displacement than the PFLP in the neutral fracture line in the sagittal plane. The 3CS group demonstrated poor mechanical stability for Pauwels type III fractures.Conclusion Regardless of the fracture line in the sagittal plane, the 3CS+MBP showed better biomechanical behaviors than the 3CS, DHS+CS, and PFLP. In addition, in contrast to the DHS+CS, the PFLP displayed less vertical and rotational displacement in the anterior and posterior fracture lines in the sagittal plane.

Paper 34: Kinematic Analysis of Lateral Meniscus Oblique Radial Tears in Anterior Cruciate Ligament Reconstructed Knees: Untreated versus Repair versus Partial Meniscectomy

Objectives:Objectives: Previous analyses have characterized the incidence of lateral meniscus oblique radial tears (LMORT) commonly seen with ACL tears, and their impact on joint and meniscus stability in the presence of ACL deficiency.Purpose:To determine the clinically relevant kinematics associated with LMORT lesions untreated versus arthroscopic repair versus partial meniscectomy in combination with anterior cruciate ligament reconstruction (ACLR).Methods:Sixteen cadaver knees underwent robotic testing for anterior drawer (AD) and pivot shift (PS) simulations at multiple knee flexion angles in intact and ACL-deficient states, followed by sequential testing of arthroscopic ACL reconstruction (ACLR), creation of a LMORT 3 lesion, LMORT 3 repair, and partial meniscectomy (PM; n=8). The same testing sequence was performed for LMORT 4 lesions (n=8). Changes (Δ) from the intact state for anterior translation, internal rotation, and valgus displacements, as well as ultrasoundographic measurements of meniscal extrusion, were measured and comparatively analyzed.Results:ACLR restored kinematics in ACL-deficient knees to intact levels for all metrics tested.For AD, ACLR + LMORT3 tear and PM resulted in significantly greater anterior translation (0.8-2.1 mm differences) compared to ACL-intact at all angles (P < 0.05) and compared to ACLR at 60o and 90o (P < 0.014). For PS, ACLR + LMORT3 tear had significantly more anterior translation (1-1.4 mm differences) at 15o than intact knees (P=0.041), and at 0o and 15o for PM (P < 0.03).ACLR + LMORT4 tear and PM resulted in significantly greater anterior translation (0.9-2.3 mm differences) for AD (P < 0.04) and PS testing (P < 0.05) compared to intact and ACLR knees at all angles tested. ACLR+LMORT 3 repair and ACLR+LMORT4 repair restored kinematics to ACLR and intact levels at all angles tested.ACLR + LMORT3 tear (P < 0.008) and both LMORT4 tear and PM (P < 0.05) resulted in increased meniscal extrusion (1.8-11 mm differences) compared to intact and ACLR statuses at all tested angles for AD and PS while repairs restored meniscus stability to ACLR and intact levels.Conclusions:Untreated LMORT 3 and 4 tears increased anterior translation, pivot shift, and meniscus extrusion even after ACLR, while partial meniscectomy further exacerbated these detrimental effects. In contrast, arthroscopic side-to-side repair of LMORT lesions effectively restored measured knee kinematics.UPLOAD-https://planion-client-files.s3.amazonaws.com/AOSSM/blobs/6bf43418-abf1-49bd-b78b-cc0c501a2da0/1/AOSSM__Images.docx UPLOAD-https://planion-client-files.s3.amazonaws.com/AOSSM/blobs/b0f0bf53-a166-4cec-bf73-176ea452b905/1/AOSSM__CHART.docx

Flexible positioning of a large area detector using an industrial robot.

The DIAD beamline for Dual Imaging and Diffraction at Diamond Light Source has opted to use an industrial robot to position its Dectris Pilatus 2M CdTe diffraction detector. This setup was chosen to enable flexible positioning of the detector in a quarter-sphere around the sample position whilst reliably holding the large weight of 139 kg of detector, detector mount and cabling in a stable position. Metrology measurements showed that the detector can be positioned with a linear repeatability of <19.7 µm and a rotational repeatability of <16.3 µrad. The detector position stays stable for a 12 h period with <10.1 µm of movement for linear displacement and <3.8 µrad for rotational displacement. X-ray diffraction from calibration samples confirmed that the robot is sufficiently stable to resolve lattice d-spacings within the instrumental broadening given by detector position and beam divergence.

Fibre-optic measurement of strain and shape on a helicopter rotor blade during a ground run: 2. Measurement of shape

Optical fibre strain and shape measurement sensors were deployed on a rotor blade during a full-speed helicopter ground run, with real-time data wirelessly streamed from rotor hub-mounted sensor interrogators. In part 2 of a 2-part paper series, two-dimensional direct fibre-optic shape sensing (DFOSS), using fibre segment interferometry-based interrogation is investigated. The concept of blade shape change visualisation over one rotation period using rotation displacement surfaces is introduced and the usefulness of DFOSS data to gain additional insights by determining operational modal frequencies independently for both horizontal and vertical vibration directions of the blade is demonstrated.

Dynamic Variation of Responsive Metal-Organic Frameworks toward Specific Stimuli

The studies on dynamic changes in metal-organic frameworks (MOFs) induced by various external stimuli have attracted great attention in various fields and have been continuously investigated since the appearance of MOFs, porous crystalline materials. Many interesting phenomena occurred in frameworks, for example, breathing, swelling, linker rotation and subnetwork displacement, as well as solid-state transformation accompanying with bond formation/deformation are observed and investigated through advanced techniques. In this account, we will summarize our efforts to expand the related research field, focusing on the dynamic changes induced by specific stimuli, including guest molecules (gas, solvent, and other organic molecules) and UV irradiation, as well as an elucidation for interesting applications achieved the responsive MOFs.

Comparison of axial-rotational postoperative periprosthetic fracture of the femur in composite osteoporotic femur versus human cadaveric specimens: A validation study.

Postoperative periprosthetic femoral fracture following hip replacement has been the subject of many varied experimental approaches. Cadaveric samples offer realistic fit and fracture patterns but are subject to large between-sample variation. Composite femurs have not yet been validated for this purpose. We compared the results of composite femurs to cadaveric femurs using an established methodology. In vitro postoperative periprosthetic fracture results using axial-rotational loading were compared between 12 composite femurs and nine fresh frozen femurs, which were implanted with an otherwise identical collarless (6 composite vs 4 cadaveric) or collared (6 composite vs 5 cadaveric) cementless femoral stem using identical methodology. Fracture torque and rotational displacement were measured and torsional stiffness and rotational work prior to fracture were estimated. Fractures patterns were graded according to the Unified Classification System. Fracture torque, displacement, torsional stiffness and fracture patterns for cadaveric and composite femurs were similar between groups. There was a trend for a greater rotational displacement in the cadaveric groups, which lead to a decrease in torsional stiffness and a significantly greater rotational work prior to fracture for all cadaveric specimens (collarless stems: 10.51 [9.71 to 12.57] vs 5.21 [4.25 to 6.04], p = 0.01 and for collared stems: 15.38 [14.01 to 17.05] vs 5.76 [4.92 to 6.64], p = 0.01). Given comparable fracture torque and the similarity in fracture patterns for fracture trials using composite samples versus cadaveric femurs, the use of composite femur models may be a reasonable choice for postoperative periprosthetic femoral fracture studies within certain limitations.

Advancements on bifurcation behavior and operational deflection shapes of disk brake creep groan

Disk brake creep groan vibrations are friction-induced stick–slip vibrations. Their impulse-like excitation, caused by the physical properties of the frictional contacts, leads to strongly nonlinear vibrations of brake system, axle and also chassis parts. As with many nonlinear phenomena, theoretical and experimental investigations on the bifurcation behavior were already done. So-far performed experiments used either strongly reduced setups or were limited in the controllability of testing, leading to certain deviations and a reduced complexity compared to the real-world behavior of the full vehicle. In this work, an approach based on half-axle tests is presented. Here, tire and rim are part of the system. By running drum-driven test matrices, extended stability maps of the rest position were created. An operational deflection shape (ODS) analysis over all 72 operating points of the test matrix was performed. Together with the relative speeds in the friction contact, a novel classification of creep groan phenomena is presented. These results prove an interaction between longitudinal and rotational axle displacements during creep groan, which was already assumed in corresponding vehicle tests. The insights enable a clearer distinction of creep groan, which is necessary for the accurate objective rating of creep groan phenomena in industry. Furthermore, the ODS results suggest the structure for a sufficient minimal model.

Influence of Varying Tensile Stress on Domain Motion.

Magnetic domain motion has been widely studied in the fields of spintronics, nanowires, and thin films. However, there is a lack of such studies on industrial steels, especially for domain motion under the action of varying stress. Understanding domain motion under stress is helpful for the improvement of evaluation accuracy and the establishment of theoretical models of passive, nondestructive testing technology. This paper presents the influence of varying tensile stresses on the magnetic domain motion of silicon steel sheets. Magnetic domain rotation and domain wall displacement were characterized using magnetic domain images, and their motion mechanisms under elastic and plastic stresses are presented. The results show that the domain rotation under stress involves reversible and irreversible changes. The effect of material rearrangement on domain rotation and domain wall displacement after plastic deformation is discussed. Based on the motion mechanism, a threshold stress value (TSV) required for the complete disappearance of the supplementary domains in the elastic range is proposed, enabling the classification of the elastic stress ranges in which the reversible and irreversible domain rotations occur. In addition, the effect of microstructure on TSV is also discussed, and the results show that the regions far away from the grain boundary need larger stresses to complete an irreversible domain rotation. Additionally, the domain width and orientation also affect the TSV. These findings regarding the domain motion mechanism and TSV can help to explain the sequence of domain rotation under stress and modify the stress assessment under dynamic loads in electromagnetic nondestructive evaluation, especially in the magnetic memory method.

A Moir\xe9 interference pattern formation of magnetic nanoparticles by rotational magnetic field controlled interfacial self-assembly

‘Magic-angled’ structure currently attracts increasing attention from condensed matter physics due to its amazing performance in superconductivity of graphene. The similar pattern formation of nanoparticles will bring about novel physics in nanoscale that causes the next generation nanodevices. However, it remains a challenging task to acquire such patterns by self-assembly process. In this article, we reported a Moiré interference pattern formation of magnetic nanoparticles regulated by a rotational magnetic field. The colloidal concentration, the strength, and the frequency of magnetic field were found to affect the pattern formation. The mechanism lied in a two-step process. First, the magnetic nanoparticles formed bilayers of superlattice driven by hydrophobic interaction of interfacial self-assembly. Then, the bilayers of superlattice yielded asynchronous rotational displacement resulting from the magnetic force so that the Moiré interference pattern of nanoparticles formed. This fabrication methodology based on the field-controlled self-assembly provided a novel and simple means to get ‘magic angled’ structures in nanoscale that will enrich the physical understanding of nanotechnology.