Step Displacement Research Articles

Focus-Switchable Piezoelectric Actuator: A Bionic Thin-Plate Design Inspired by Conch Structure

Traditional camera zoom mechanisms, relying on stepper motors and intricate transmission components, suffer from bulky designs that restrict their applicability in compact systems. This study presents a novel piezoelectric focus-switchable mechanism (PFSM) directly driven by a biomimetic radial-mode piezoelectric actuator (RMPA) with inclined driving structure mimicking the conch shell. The PFSM utilizes rotational motion for optical zoom, providing a more compact and efficient alternative to conventional linear motion-based systems. By utilizing finite element method (FEM) optimization, we developed a compact prototype (34×34×3mm³, 14.83g) and experimentally verified its performance, achieving a peak rotational speed of 1573.14 RPM, torque output of 3.6 mN·m, and step displacement resolution of 45.8 μrad. These attributes enable smooth lens module switching for optical zoom, thus demonstrating the mechanism’s feasibility. Importantly, the PFSM offers precise positioning without relying on additional transmission parts and features a self-locking capability when de-energized, rendering it an ideal choice for camera zoom applications. In summary, this study underscores the PFSM’s potential as a compact, lightweight, and efficient camera zoom mechanism, contributing meaningfully to the field of imaging technology and optical systems.

A Study on Historical Big Data Analysis of Surface Ecological Damage in the Coal Mining Area of Lvliang City Based on Two Mining Modes

Coal mining inevitably causes damage to the surface ecological environment. In response to the characteristics of multiple factors, wide scope, and long time series of surface ecological environment damage in coal mining subsidence areas, how to integrate multiple data sources and monitoring methods to achieve monitoring and trend analysis of ecological damage throughout the entire mining cycle still needs to be studied. In addition, the 110 mining method provides an innovative method for underground coal mining to reduce its surface ecological damage, but the differences in surface damage between the two mining modes and the effectiveness of the 110 method in realizing surface ecological damage-reducing mining still need to be studied in depth. Therefore, this study takes the surface ecological damage in the mining area of Lvliang City, a typical resource city in Shanxi Province, China, as the object. It establishes a four-in-one “Satellite–UAV–Ground–Underground” information monitoring method, proposes a historical big data evolution analysis method, constructs three spatial scales of historical big databases, clarifies the current situation and development trend of damage in coal mining areas in Lvliang City and explores the differences in surface ecological environment damage characteristics in coal mining areas based on the 121 and 110 mining methods. The results show that: (1) The existing coal mining subsidence area in Lvliang City is as high as 92,191.47 hectares, and it is expected to continue to increase to 130,739.55 hectares in the future 2035, with a growth rate of 41.812%, which realizes the goals of mapping the current situation, retracing the history and predicting the future of the ecological damage of the surface in Lvliang City. (2) The surface NDVI of the 110 working face is restored to the average level of the mining area faster than that of the 121 working face. The surface crack width, step displacement, length, distribution density, and surface settlement height of the 110 working face are all smaller than those of the 121 working face. It has been verified that the unique top-cutting and swelling filling effect of the 110 methods can effectively reduce the ecological damage caused by coal mining subsidence. And its widespread application can effectively realize the ecological environmental protection of the coal mine area and contribute to the high-quality development of the coal industry in Lvliang City.

Master Curves for Poroelastic Spherical Indentation With Step Displacement Loading

Abstract Theoretical and numerical analyses are conducted to rigorously construct master curves that can be used for interpretation of displacement-controlled poroelastic spherical indentation test. A fully coupled poroelastic solution is first derived within the framework of Biot’s theory using the McNamee–Gibson displacement function method. The fully saturated porous medium is assumed to consist of slightly compressible solid and fluid phases and the surface is assumed to be impermeable over the contact area and permeable everywhere else. In contrast to the cases in our previous studies with an either fully permeable or impermeable surface, the mixed drainage condition yields two coupled sets of dual integral equations instead of one in the Laplace transform domain. The theoretical solutions show that for this class of poroelastic spherical indentation problems, relaxation of the normalized indentation force is affected by material properties through weak dependence on a single-derived material constant only. Finite element analysis is then performed in order to examine the differences between the theoretical solution, obtained by imposing the normal displacement over the contact area, and the numerical results where frictionless contact between a rigid sphere and the poroelastic medium is explicitly modeled. A four-parameter elementary function, an approximation of the theoretical solution with its validity supported by the numerical analysis, is proposed as the master curve that can be conveniently used to aid the interpretation of the poroelastic spherical indentation test. Application of the master curve for the ramp-hold loading scenario is also discussed.

A centipede-inspired bonded-type ultrasonic actuator with high thrust force density driven by dual-torsional-vibration-induced flexural traveling waves

This paper presents an ultrasonic actuator with high thrust force density driven by dual-torsional-vibration-induced flexural traveling waves. Here, the PZT plates are bonded onto a duralumin vibrating body in a block shape to accomplish a compact configuration and they operate in the 2nd torsional vibrations, whose strong electromechanical coupling effect facilitates the enhancement of the driving force. Interestingly, the operating principle somewhat imitates the movement pattern of the centipede’s feet. To test the validity, first, by using a Mason-equivalent-circuit-based dynamic model, several key dimensions were tuned to increase the driving-force-to-weight ratio. Meanwhile, the driving feet’s configurations are adjusted based on a kinetic model to make the elliptical motion shape close to a circle. Then, an actuator prototype with the size of 48 × 47 × 6 mm3 and the weight of 29 g was fabricated and the moving/loading/positioning performance was evaluated. When the actuator adopts a continuous operation, its maximal sliding speed reached 630 mm/s at the frequency of 24.95 kHz. Moreover, it yielded the maximal thrust force and the maximal output power of 4.38 N and 527.8 mW, corresponding to the thrust force density and the power density of 151.2 N/kg and 18.2 W/kg, respectively. In a stepping operation, the minimal step displacement was 0.91 μm. These results demonstrate that the dual-torsional-vibrations-induced traveling wave allows the actuator to produce the high thrust force density and provides a new actuating principle to design powerful ultrasonic actuators.

Determining technological parameters for obtaining ta15 titanium alloy blanks with improved mechanical characteristics using the electron-beam 3D printing method

The object of this study is the process of electron beam 3D printing of articles made of TA15 titanium alloy powder. Peculiarities of the structure and properties formation of alloy blanks, obtained by this method have been described. Influence of process parameters (electron beam power and geometric scanning parameters) on the characteristics of the material were considered. Step of displacement of the beam trajectory changed from 0.1 to 0.25 mm with an interval of 0.05 mm. Specific energy of the electron beam varied from 20 to 70 J/mm3 for every trajectory displacement step. The macrostructure was examined visually while the microstructure was studied by optical microscopy. Mechanical properties were determined by uniaxial tension and impact bending tests. It was established that depending on the 3D printing parameters the macrostructure of most samples is dense but with unfavorable parameters non-fusions or shrinkage porosity defects may form. The microstructure of the dendritic type has an α´+β lamellar-acicular morphology, its dispersity and shape of α´–phase areas vary depending on the process parameters. A scanning step of 0.2 mm and a beam energy of 40 J/mm3 allows obtaining a dispersed microstructure in which there are no non-fusions and shrinkage micropores. The value of the Rm is 27 %, and the R0.2 is 24 % higher than that of the alloy obtained by the conventional technology of electron beam melting. The A5 is 3.2 times higher. However, impact toughness of the sample with dendrite unfavorable orientation to the direction of load applying may be lower compared to conventional technology. The results could be used for devising commercial technology of high strength titanium alloys parts produced by 3D printing

An investigation of a self-powered low-frequency nonlinear vibration isolation system

High-static-low-dynamic stiffness vibration isolation are of utmost significance in low-frequency vibration isolation. However, their intricate mechanisms are always challenging for environmental vibration changes. In this study, a self-powered nonlinear vibration isolation system with two stages is studied, with the aiming of obtaining the broadband vibration isolation. Magnetic springs of negative stiffness combined with the coil could transform mechanical vibration into electrical energy in lower stage. The feedback electrical energy could power the piezoelectric actuator in the upper stage. Based on the governing equations measured in stable equilibrium, the harmonic balance analysis is used to derive the frequency response functions of the transmissibility and the output power in the mechatronic resonance. The frequency band of vibration isolation extends to the lower frequencies and two resonance peaks reduce to the lower levels. The numerical simulations results validate the analytical solutions. Then the shock isolation performance is illustrated under the round step displacement and rounded pulse displacement. The parameter study demonstrates numerically that introduction of the high-static-low-dynamic stiffness improves the shock isolation performance. Moreover, the lower stage mechanical energy could drive the piezoelectric stack, resulting in high-efficiency shock isolation. Finally, an experiment is employed to prove the high-efficiency vibration isolation.

On straightness measurements of large CNC machine tools

The CNC (computerized numerically controlled) machines are widespread in use due to their high capability of precise manufacturing in industrial production. They have a wide range of designs depending on the working capacity in manufacturing. The associated form errors in large-capacity CNC machines during production shall be identified and corrected or eliminated. This study presents an investigation of one of the main form errors that may affect the manufacturing precision of these machines. This error type is a straightness error with both two kinds of horizontal and vertical errors. The study is carried out for a vertical turning center CNC machine type. The straightness errors are measured for the X axis at different latches in the Z direction and for the Z axis at three positions in the X direction with multi-displacement steps. Different algorithms are used in the determination of straightness errors. The X-axis has minimum horizontal straightness errors at latch Nr. 3 and minimum vertical straightness errors at latch Nr. 5. For the Z axis, the minimum values for horizontal and vertical straightness errors exist when the spindle is located 1200 mm away from the machining center to the right. The displacement steps have a significant impact on the determination of straightness errors.

Numerical analysis of the indentation of a poro-elastoplastic half space by a rigid cylinder

Poro-elasto-plastic cylindrical indentation as a means for material characterization is explored numerically in this work. When a rigid cylinder is being pressed into a semi-infinite, fully saturated poroelastic medium via step displacement loading, undrained and drained elastic constants are reflected in the responses at the early and late times, while hydraulic diffusivity is manifested in the transient behavior. Such an indentation test can therefore be used in principle to identify material parameters. For geomaterials, plastic deformation may occur due to the indentation action. How the hydromechanically coupled indentation response is affected by plastic deformation is investigated here using finite element analysis. We consider the problem to be plane strain with frictionless contact. Drucker-Prager failure criteria with and without a cap are considered. We show that if there is only limited plastic deformation, the concept of using the transient response for determining hydraulic diffusivity may be extended from poroelasticity to poro-elasto-plasticity.

Step Displacement Improving Method of Inertial Actuated Piezoelectric Robot Based on Diagonal Deformation Trajectory

For the miniature piezoelectric robots operated by inertial driving method, the step displacements were limited by the deformations of the inertial units. Thus, a diagonal inertial driving method (DIDM) was proposed in this work to increase the step displacement. The prominent feature of DIDM was that the inertial force was in diagonal direction by using the designed piezo-leg with square cross-section. The vertical component of the inertial force reduced the friction force and even made the robot jump to achieve a larger step displacement. Experimental results indicated that the proposed DIDM increased the step displacement successfully. The increase effect was optimal when the vertical component of the inertial force was equal to the horizontal one, and the realized step displacement was as high as 156% to the deformation of the inertial unit in motion direction. Moreover, the force and displacement responses of the driving foot in vertical direction were measured, which indicated that the robot realized jumping action to increase the step displacement under DIDM, and the maximum speed realized by DIDM was 2.3 times of that achieved by TIDM. We believe that the proposed DIDM can broaden the solutions of improving the performances of the inertial miniature piezoelectric robots.

A miniature piezoelectric actuator with fast movement and nanometer resolution

To accomplish fast movement and high positioning capability, a miniature self-moving piezoelectric actuator (MSPA) is developed with two groups of polyphenylene sulfide (PPS) transducers operating in the symmetric bending (SB) or counter symmetric bending (CSB) vibration. Each group includes the inner and outer legs, whose vibrations are orthogonal and horizontal to the ground, respectively; this interestingly imitates the stepping and swing functions of the forelimbs and hindlimbs of the gorilla in the ‘running on all fours’ gait. To examine the validity, first, by utilizing the model on the basis of Krimhertz transmission theory, the resonant frequency of the CSB vibration was structurally tuned to approach that of the SB vibration. Then, a MSPA prototype with the size of 30 × 45 × 49 mm and the weight of 25.2 g was fabricated to assess the moving, carrying, and positioning performance. In a tethered manner, the MSPA yielded the maximal speed of 562 mm/s (18.73 body length per second), the maximal payload of 485 g (19.25 times of its own weight), and the towing force of 0.5 N (corresponding to the towing force density of 19.8 N/kg). Moreover, it achieved the turning movements (whose directions, angular speeds, and steering radii are changeable) and in-situ rotations, climbed the slope of 12.5°, and moved on the curved floor. In an untethered manner, the MSPA produced the minimal step displacement of 31.9 nm. These results demonstrate that the MPSA possesses the large speed and the nanometer resolution owing to the bionic operating principle and the employment of PPS, and provides a new approach to design lightweight piezoelectric actuators.

An Efficient Penalty Method without a Line Search for Nonlinear Optimization

In this work, we integrate some new approximate functions using the logarithmic penalty method to solve nonlinear optimization problems. Firstly, we determine the direction by Newton’s method. Then, we establish an efficient algorithm to compute the displacement step according to the direction. Finally, we illustrate the superior performance of our new approximate function with respect to the line search one through a numerical experiment on numerous collections of test problems.

Investigation of HIFU beam propagation through acoustic holograms in water

We investigated variations in the HIFU beam of a clinical system as it traverses acoustic holograms—small artificial objects of different types—within a tank that was filled in with the degassed deionized water. The pressure distribution within the HIFU beam was assessed in multiple planes perpendicular to the beam axis. The ultrasound transducer with the focal length of 14 cm inside the Sonalleve table top (Profound Medical, Mississauga, ON, Canada) generated the focusing ultrasonic beam, which propagated through the water. Each hologram was positioned 3 cm below the focal plane, with precise adjustments of positions and angles for each measurement. Pressure measurements were conducted using the needle hydrophone HNA-0400 (ONDA Corp, Sunnyvale, CA, USA) mounted on a 3D positioning system. The motors of the positioning system were controlled, and pressure values were recorded using a GUI generated in LabVIEW. The displacement step created by the motors on each axis was 0.01 mm. The properties of the holograms were reconstructed, considering the experimental data obtained. Our findings demonstrated that the shape, size, elasticity, and placement of each acoustic hologram significantly influenced the observed field pattern. This work was supported by the German Federal Ministry of Education and Research (“MR-HIFU-Pancreas”, FKZ:13GW0364D).

Determining the influence of technological parameters of electron beam surfacing process on the microstructure and microhardness of Ti-6Al-4V alloy

This paper reports the devised technology and equipment for manufacturing parts and assemblies with pre-defined properties by 3D printing methods. Underlying the technology is the application of a high-power electron beam to fuse metal powder in a vacuum chamber with the formation of successive layers that repeat the contours of the digital model of the product. The object of research is the process of surfacing products made of Ti6Al4V titanium alloy powder. The influence of technological parameters (speed and power of the electron beam) on the formation of the structure of the deposited metal and its mechanical properties was investigated. 3 samples printed under 3 modes were studied: beam speed, 270, 540, and 780 mm/s; power, 240, 495, and 675 W, respectively. The beam energy density was 44.5 J/mm3; the trajectory displacement step was 0.2 mm; the dynamic focusing current Idf was –0.31 A; and the powder layer thickness was 0.1 mm. The samples were examined by conventional methods. The structures were studied using an optical microscope, images were recorded with a camera. The Vickers hardness was measured with a microhardness meter in the direction from the technological supports to the surface of the sample, as well as along the surface of the product, and in the layers of the middle part of the sample. It was established that the articles had a dense cast structure of surfaced metal. On all samples, large crystallites with a uniform lamellar-acicular structure of α´-phase with a small amount of β-phase are formed along the height, mostly without defects with uniform microhardness both along the height and along the surface. It was determined that the surfacing mode at beam speed, 240 mm/s; power, 270 W is the most rational for practical use. Under this mode, a stronger structure is formed when it is crushed, reducing the width of the crystallites by 1.55 and 1.17 times compared to other modes

A millipede-inspired miniature self-moving ultrasonic actuator with high carrying capability and nanometer resolution

To accomplish high carrying/positioning capability with compact structure, in this study, a miniature self-moving ultrasonic actuator (MSMUA) is developed by exciting a flexural traveling wave induced by dual longitudinal vibrations. Here, four lead-zirconate-titanite plates are bonded onto the bilateral ends of the bar-shaped vibrating body to efficiently generate the vibration. Interestingly, the MSMUA imitates the millipede in terms of the simple configuration and the operating principle. To test the validity, first, by using a Krimhertz-transmission-theory-based model, the key dimensions were adjusted to not only increase the driving-force-to-weight ratio but also make the elliptical motion shape close to the unity. Then, a prototype with the size of 87.5 × 9 × 9 mm3 and the weight of 15.67 g was fabricated, its moving/carrying/positioning performance was evaluated, and an array of MSMUAs was constructed to achieve flexible movement. At 105.44 kHz working frequency, the MSMUA in a tethered manner yielded the maximum payload of 433 g (equal to 27.7 times of its own weight), the maximum speed of 378 mm/s, and the maximum towing force of 0.4 N. Meanwhile, it crossed the gully 21 mm in width and climbed the slope of 7.4° Installed with an onboard circuit and 3.7 V batteries, the MSMUA provided the minimum step displacement of 19.2 nm. Moreover, the array of MSMUAs produced the turning movements (whose directions, angular speeds, and steering radii were adjustable) and the in-situ rotations. This study demonstrates the MSMUA's high carrying capability and nanometer resolution, and provides a new approach to design powerful ultrasonic actuators.

Force relaxation response in the poroelastic axisymmetric Boussinesq problem for an indenter of arbitrary profiles I: Permeable and impermeable surface drainage conditions

In this study, we have derived a theoretical solution for the poroelastic axisymmetric Boussinesq problem when an indenter with arbitrary profiles is subjected to step displacement loading. The analysis is conducted within the framework of Biot’s theory, employing the McNamee–Gibson displacement function method. We explore two distinct scenarios for surface drainage boundary conditions: one where the surface allows full permeability and another where it is fully impermeable. The formulation of the mechanical boundary condition at the surface relies on an equation that establishes the relationship between the depth of indentation and the contact radius. Our solution encompasses two aspects: force asymptotes at the undrained and drained limits, and a normalized force relaxation that accounts for transient responses. Specific findings are presented for three indenter shapes: paraboloidal, conical, and cylindrical. Of particular significance, we demonstrate that for these specific indenter shapes, the normalized force relaxation at ω=0 can be expressed in closed form in the Laplace domain. In addition to this analytical breakthrough, we conducted numerical simulations employing actual indenters. Remarkably, the normalized force relaxation curves from actual indenters show negligible dependence on material properties and closely align with our closed-form solution at ω=0. This finding suggests that the closed-form solution could act as a universal master curve capable of characterizing the normalized force relaxation response in instances of a real indenter, irrespective of material properties.

Step-like displacement prediction and failure mechanism analysis of slow-moving reservoir landslide

Landslides triggered by extreme rainfall due to global climate change are becoming more frequent. The Earth surface processes activity and landform evolution caused by landslide movement seriously affect human survival and the environment. In recent years, the reservoir slope located in the Three Gorges reservoir (TGR) area has been subject to the combined effects of extreme rainfall and reservoir regulation, which have been highly susceptible to inducing landslides. Reservoir landslides usually show step-like slow movement characteristics. The causes of slow-moving landslides are complex, the mechanisms behind them are difficult to grasp, and it may evolve into violent landslide disasters. Therefore, accurately predicting step-like displacement in slow-moving landslides is an effective solution for risk reduction. To achieve the accurate prediction of the step-like displacement of slow-moving landslides and the analysis of the failure mechanism, this study establishes a prediction model applicable to step-like displacement prediction of slow-moving reservoir landslides is developed based on 16 years of continuously monitored cumulative displacement of the Jiuxianping landslide, combined with the Empirical Mode Decomposition (EMD) method and the Improved Particle Swarm Optimization (IPSO) optimized the Long short-term memory (LSTM) neural network. This approach can effectively improve step-like displacement prediction accuracy. In particular, this approach can better represent the association between the step displacement of slow-moving landslides with environmental characteristics (e.g., rainfall, reservoir level). The study reveals that there are differences in the mechanisms and influencing conditions that cause the deformation of different areas of the landslide. Additionally, the reservoir water level fluctuation and seasonal rainfall are identified as the primary reasons contributing to the stepped displacement of the Jiuxianping landslide. The method provides a basis for the step-like displacement prediction, instability mechanism and landform evolution study of slow-moving reservoir landslides and provides valuable guidance for the prevention and control of similar reservoir geomorphic hazards worldwide.

Reaching Large Strains During Simple Shear Experiments Thanks to Sequential Re-Machining of the Free Edges

BackgroundThe simple shear experiment is widely used for the calibration of plasticity models due to straightforward post processing. The specimen can be as simple as a rectangular strip of sheet metal, but the maximum strain is limited by early initiation of fractures from the free edges. Avoiding this drawback has been a major motivation for the development of new specimens with optimized edge geometries or the in-plane torsion test, but at the cost of a more complex analysis of the test and often a reduction of the gauge section.ObjectiveThe objective of the present work is to overcome the initiation of fracture from the free edges during simple shear experiments. Our goal is to double the achievable maximum strain, while keeping the size of the specimen and the post processing simplicity of a standard simple shear test.MethodsA sequential single shear test is proposed, consisting of several two steps sequences on a notched geometry. First, an interrupted shear test is performed up to a specified displacement value. Then, the damaged free edges of the specimen are removed through milling. The specimen is then ready for the following sequence of shear and re-machining.ResultsExperiments are performed on three engineering materials, with up to five loading-machining sequences. The maximum attained effective strain is up to two times the one reached during a monotonic experiment. Numerical simulations are used to validate the shear stress and strain calculations from experimental measurements. Practical recommendations are derived for the choice of the displacement step size and Digital Image Correlation analysis.ConclusionIt is found that the maximum strain attained before the undesired failure of the specimen during simple shear test can be substantially extended through repeated re-machining of the specimen boundaries, enabling behavior identification at larger strains.

Effect of O-arm on reduction quality and functional recovery of acetabular dome impaction fractures: a retrospective clinical study

BackgroundAcetabular dome impaction fractures (ADIF) are difficult to reduce and have a high failure rate. Consistency between the acetabulum and the femoral head is usually assessed using intraoperative X-ray fluoroscopy to evaluate the quality of fracture reduction. This study examines the effects of intraoperative mobile 2D/3DX imaging system (O-arm) on the reduction quality and functional recovery of ADIF.MethodsWe retrospectively analysed the data of 48 patients with ADIF treated at Honghui Hospital between October 2018 and October 2021.The patients were divided into the X-ray and O-arm groups. The residual step-off and gap displacements in the acetabular dome region were measured, and fracture reduction quality was evaluated. Hip function was evaluated using the modified Merle d’Aubigné and Postel scoring systems.ResultsThere were no significant intergroup differences in the preoperative general data (p > 0.05). The mean residual average step displacement in the acetabular dome region was 3.48 ± 2.43 mm and 1.61 ± 1.16 mm (p < 0.05), while the mean gap displacement was 6.72 ± 3.69 mm and 3.83 ± 1.67 mm (p < 0.05) in the X-ray and the O-arm groups, respectively. In the X-ray group, according to the fracture reduction criteria described by Verbeek and Moed et al., one case was excellent, 13 cases were good, 11 cases were poor; 56% were excellent or good. In the O-arm group, seven cases were excellent, 12 cases were good, and four cases were poor; overall in this group, 82.6% were excellent or good (p < 0.05). A total of 46 patients achieved fracture healing at the last follow-up. In the X-ray group, according to the modified Merle d’Aubigné and Postel function score, three cases were excellent,12 cases were good, six cases were middle, three cases were poor; 62.5% were excellent or good, In the O-arm group, 15 cases were excellent, four cases were good, two cases were middle, one case was poor; 86.4% were excellent or good (p < 0.05).ConclusionsThe application of O-arm in ADIF can improve fracture reduction quality and functional recovery.

A novel method for continuous chromatographic separation of monoclonal antibody charge variants by combining displacement mode chromatography and step elution.

Charge heterogeneity of monoclonal antibodies is considered a critical quality attribute and hence needs to be monitored and controlled by the manufacturer. Typically, this is accomplished via separation of charge variants on cation exchange chromatography (CEX) using a pH or conductivity based linear gradient elution. Although an effective approach, this is challenging particularly during continuous processing as creation of linear gradient during continuous processing adds to process complexity and can lead to deviations in product quality upon slightest changes in gradient formation. Moreover, the long length of elution gradient along with the required peak fractionation makes process integration difficult. In this study, we propose a novel approach for separation of charge variants during continuous CEX chromatography by utilizing a combination of displacement mode chromatography and salt-based step elution. It has been demonstrated that while the displacement mode of chromatography enables control of acidic variants ≤26% in the CEX eluate, salt-based step gradient elution manages basic charge variant ≤25% in the CEX eluate. The proposed approach has been successfully demonstrated using feed materials with varying compositions. On comparing the designed strategy with 2-column concurrent (CC) chromatography, the resin specific productivity increased by 95% and resin utilization increased by 183% with recovery of main species >99%. Further, in order to showcase the amenability of the designed CEX method in continuous operation, the method was examined in our in-house continuous mAb platform.

Magnetic tunnel junction platforms for linear positioning and nanoscale displacement sensing

An array of magnetic tunnel junctions (MTJs), connected in a Wheatstone bridge, is characterized as a positioning sensor to detect spatial displacement of a magnetized object. To perform the experiment, the sensor was mounted on a fixed frame, and the magnet was installed on top of nano-positioning piezo-stage, operating in a closed-loop feedback circuit. The sensor signal was recorded in time domain, to detect displacement of the magnet, defined by commands to the stage. The positioning transfer curves were obtained for different orientations of magnetization with respect to the direction of the magnet displacement and the field sensing direction of the MTJs in the arrays. For configurations with linear transfer curve between positioning displacements and the sensor signal, the effects of magnet size, sensor pattern dimensions and interspace distance between the sensor and magnet positioning trajectories, are characterized. In the optimized experimental configuration, the displacement steps down to 10 nm were detected.