Force Modulation Research Articles

Proton acceleration driven by relativistic femtosecond Laguerre–Gaussian lasers

AbstractWith the advancement of ultra-intense and ultra-short laser technology, lasers have achieved new parameters in femtosecond (10–15 s) and petawatt (1015 W) ranges. Ion acceleration driven by these lasers has become a prominent research area. However, most research still relies on traditional Gaussian lasers, posing challenges in enhancing the low divergence angle, high flux, and high collimation of ion beams. This paper reviews a novel laser mode—the Laguerre–Gaussian (LG) laser in the relativistic domain. LG lasers feature a hollow intensity distribution and angular momentum, offering centripetal force and phase modulation at the axis center, reducing particle beam divergence and enabling focused acceleration. High-quality proton beams driven by ultra-intense, ultra-short LG lasers have promising applications in proton therapy, fast ignition in inertial confinement fusion, proton imaging, particle injection in accelerators, and astrophysics.

Naturally Inspired Tree-Ring Structured Dressing Provides Sustained Wound Tightening and Accelerates Closure.

Mechanically regulated wound dressings require a rational combination of contraction and adhesion functions as well as balancing exudate-induced swelling issues. However, many of the reported dressings face the dilemma of impaired function and impeded wound self-contraction due to fluid-absorbing swelling. In this study, inspired by the tree ring, a core-ring structured hydrogel dressing capable of mechanical modulation is designed, and prepare it using a simple two-step photopolymerization process. The core covers the center of the wound, contracts spontaneously at body temperature to generate a contractile force of 3.4kPa, and resists swelling. Meanwhile, the ring adheres to the normal epidermis around the wound and transfers the contraction stress to the wound edge. The integration of a functionally independent core and ring ultimately achieves effective wound traction and avoids dressing swelling. In murine and porcine skin wound-healing models, this hydrogel with a closely connected core and ring promotes healing by accelerating epidermal closure (50% closure in mouse skin on day 2, 85% closure in pig skin on day 8), collagen deposition, vascular maturation, and extracellular matrix remodeling. These results can guide further research on mechanical force modulation in wound healing, with the potential for clinical translation.

Research on Direct-Drive Brake Actuator and Its Control Method for Electric Vehicles

<div>With the rapid development of electric vehicles, the need for improved reliability and safety performance of electric vehicle braking systems has become paramount. In response to this demand, a novel direct-drive brake-by-wire actuator based on linear motors was designed to address these challenges. This article presents the structure and principles of the proposed braking actuator. Leveraging the traditional electromechanical brake systems as a foundation, the prototype was modified and fabricated. Additionally, the control and drive system for the braking actuator was established using the TMS320F28335 digital signal processor. Moreover, the current-position dual closed-loop control algorithm was devised to regulate the braking force accurately. Experimental results demonstrate that the direct-drive brake-by-wire actuator exhibits rapid responsiveness and precise braking force modulation, showcasing promising prospects in the field of electric vehicle braking.</div>

An Assist-as-Needed Control Strategy Based on a Subjective Intention Decline Model

In the rehabilitation training process for stroke patients, the level of excitement in the patient’s physiological state has a positive impact on the efficacy of the training. In order to improve patients’ initiative during training and prevent dependence on assistive systems, this study proposes an assist-as-needed control strategy based on a subjective intention decline model. The strategy primarily consists of two modules: a subjective intention decline control module and a limb movement assessment module. The subjective intention decline module collects surface electromyography (sEMG) data during patient training and optimizes support vector machine (SVM) using quantum particle swarm optimization (QPSO) algorithms to establish a subjective intention decline model. The limb movement assessment module collects information such as interaction force and position error during training and proposes a method for evaluating the motion state of the affected limb. This model combines traditional impedance control with a method for assessing limb movement and subjective status, automatically adjusting the level of assistive force on the affected limb in real time to enhance its active participation in tasks. Finally, we performed two verification experiments to assess the patient’s initiative in participating in the training. The experimental results show that the proposed method effectively reduced the average assist force by 65.66% for the traditional impedance control training system and effectively the average assist force by 35.2% for the control training system using only the assist force module based on force position information. At the same time, the accuracy of the subjective intention attenuation module established in the experiment to identify the fatigue level of the subjects reached 93.41%. Therefore, the proposed method effectively improves the initiative of trainers and also prevents patients from relying on the assist-as-needed control training system.

Grasp context-dependent uncertainty alters the relative contribution of anticipatory and feedback-based mechanisms in object manipulation

Predictive control within dexterous object manipulation while allowing for the choice of contact points has been shown to employ a predominantly feedback-based force modulation. The anticipation is thought to be facilitated through the internal representation of the object dynamics being integrated and updated on a trial-to-trial basis with the feedback of contact locations on the object. This is as opposed to the classically studied memory representation-based fingertip force control for grasping with pre-selected contact locations. We designed a study to examine this grasp context-dependent asymmetry in sensorimotor integration by introducing binary uncertainty about the grasp type before movement initiation within the framework of motor planning. An inverted T-shaped instrumented object was presented to 24 participants as the manipulandum, and they were asked to reach, grasp, and lift it while minimising the peak roll. We dissociated the planning and the execution phases by pseudo-randomly manipulating the availability of visual contact cues on the object after movement onset. We analysed both derived as well as direct kinetic and kinematic measures of the grasp during the loading phase to understand the anticipatory coordination. Our findings suggest that uncertainty about the grasp context during movement preparation resulted in a shift towards feedback-based mechanisms for grasp force modulation despite the persistence of visual cues.

Facilitating Ion Storage and Transport Pathways by In Situ Constructing 1D Carbon Nanotube Electric Bridges between 2D MXene Interlayers.

Multiple van der Waals (vdW) gaps invoke abundant opportunities for contriving artificial architectures and tailoring desired properties via the intercalation route beyond the reach of conventional concepts. Intriguingly, the electrochemical intercalation strategy can precisely and reversibly tune the intercalation stage of charged functional species. This study presents a valid structural editing protocol facilitated by electrochemical intercalation to engineer MXene interlayers, ultimately incorporating in situ constructed carbon nanotube (CNT) electric bridges for enhanced ion storage and transport pathways. The method allows for the precise modulation of electrochemical forces to tailor materials for specific applications. Deep intercalation and in situ growth processes establish robust anchoring sites and connectivity hubs between MXenes and CNTs, ensuring structural homogeneity and stability in advanced electrode materials. The results demonstrate the effectiveness of electrochemistry-mediated interlayer nanoengineering in MXenes, offering a versatile approach to design vdW heterostructures with tailored functionalities for energy storage and conversion applications. This work highlights the potential of electrochemical modulation in advancing materials engineering strategies for next-generation energy storage technologies.

Performance Optimization with LPV Synthesis for Disturbance Attenuation in Planar Motors

Optimizing the performance of motion control systems with variations in nonlinear parameters is not an easy task. To accomplish this task, it is important to design the controller using the linear system approach. In this study, a linear parameter varying (LPV) control method is proposed in which nonlinearities are treated as parameter variations for planar motors. The proposed control method consists of the force and torque modulation with the commutation scheme and the nonlinear current controller with H∞ state feedback control in the form of LPV synthesis to improve the position-tracking performance. An interpolated gain-scheduling controller based on LPV synthesis is determined by applying H∞ control to a linear matrix inequality technique. An interpolated gain-scheduling controller can attenuate disturbance without disturbance estimation. The effectiveness of the proposed control method is evaluated using simulation results and compared with the conventional proportional–integral–derivative control to verify both improved position-tracking performance and disturbance attenuation.

Tunable Coassembly of Octaarginine with Thiazolyl Benzenesulfonamides Exerts Variable Antibacterial Activity.

The cationic peptide octaarginine (R8) is a prominent cell-penetrating peptide and has been extensively researched as a carrier of diverse cell-destined cargo. In this work, we describe the coassembly of R8 with small molecule thiazolyl benzenesulfonamide (TBS) derivatives. Physical complexation of R8 with three TBS derivatives across a range of weight ratios results in the formation of a distinctive set of nano- and microstructures. A detailed structural characterization of the R8:TBS-derivative coassemblies has been performed by a combination of FTIR, XRD, SEM, and DSC. The major functional groups that facilitate coassembly include sulfonamide SO2 and NH groups of the TBS derivatives, and the guanidinium of R8, via a combination of cation-π and hydrogen-bonding interactions. The R8:4F-TBS coassembly displays singular topological features compared to R8:4Br-TBS and R8:4CH3-TBS complexes. These differences are attributed to the changes in the preferred orientation of the guanidino groups of R8 with respect to the π-surface of TBS derivatives. The modulation of forces of interaction across the R8:TBS-derivative coassemblies aligns with their respective thermal stabilities. The single-crystal structure of bare 4F-TBS has been subjected to Hirshfeld and 2D fingerprinting analysis and indicates notable variations from the crystal packing of the R8:4F-TBS coassembly. The structural differences among the R8:TBS-derivative coassemblies correlate with distinctive profiles of antibacterial activity in each case. The coassembled structures exert a variable extent of bacterial membrane disruption and damage based on the unique disposition of R8 and the potency of small molecule in each case. The aqueous suspension of R8:4F-TBS displays significant outer membrane disruption and bacterial killing compared with the other complexes. This work successfully demonstrates the hitherto unreported potential for coassembly of cell-penetrating peptides with other entities. The coassembly of R8 with small molecules highlights an attractive strategy for tuning the functional properties of each component.

Changes in high-frequency neural inputs to muscles during movement cancellation

Objective.Cortical beta (13-30 Hz) and gamma (30-60 Hz) oscillations are prominent in the motor cortex and are known to be transmitted to the muscles despite their limited direct impact on force modulation. However, we currently lack fundamental knowledge about the saliency of these oscillations at spinal level. Here, we developed an experimental approach to examine the modulations in high-frequency inputs to motoneurons under different motor states while maintaining a stable force, thus constraining behaviour.Approach.Specifically, we acquired brain and muscle activity during a 'GO'/'NO-GO' task. In this experiment, the effector muscle for the task (tibialis anterior) was kept tonically active during the trials, while participants (N= 12) reacted to sequences of auditory stimuli by either keeping the contraction unaltered ('NO-GO' trials), or by quickly performing a ballistic contraction ('GO' trials). Motor unit (MU) firing activity was extracted from high-density surface and intramuscular electromyographic signals, and the changes in its spectral contents in the 'NO-GO' trials were analysed.Main results.We observed an increase in beta and low-gamma (30-45 Hz) activity after the 'NO-GO' cue in the MU population activity. These results were in line with the brain activity changes measured with electroencephalography. These increases in power occur without relevant alterations in force, as behaviour was restricted to a stable force contraction.Significance.We show that modulations in motor cortical beta and gamma rhythms are also present in muscles when subjects cancel a prepared ballistic action while holding a stable contraction in a 'GO'/'NO-GO' task. This occurs while force levels produced by the task effector muscle remain largely unaltered. Our results suggest that muscle recordings are informative also about motor states that are not force-control signals. This opens up new potential use cases of peripheral neural interfaces.

Measurement of unsteady force on rotor blade surfaces in axial flow compressor

To assess the aerodynamic performance and vibration characteristics of rotor blades during rotation, a study of unsteady blade surface forces is conducted in a low-speed axial flow compressor under a rotating coordinate system. The capture, modulation, and acquisition of unsteady blade surface forces are achieved by using pressure sensors and strain gauges attached to the rotor blades, in conjunction with a wireless telemetry system. Based on the measurement reliability verification, this approach allows for the determination of the static pressure distribution on rotor blade surfaces, enabling the quantitative description of loadability at different spanwise positions along the blade chord. Effects caused by the factors such as Tip Leakage Flow (TLF) and flow separation can be perceived and reflected in the trends of static pressure on the blade surfaces. Simultaneously, the dynamic characteristics of unsteady pressure and stress on the blade surfaces are analyzed. The results indicate that only the pressure signals measured at the mid-chord of the blade tip can distinctly detect the unsteady frequency of TLF due to the oscillation of the low-pressure spot on the pressure surface. Subsequently, with the help of one-dimensional continuous wavelet analysis method, it can be inferred that as the compressor enters stall, the sensors are capable of capturing stall cell frequency under a rotating coordinate system. Furthermore, the stress at the blade root is higher than that at the blade tip, and the frequency band of the vibration can also be measured by the pressure sensors fixed on the casing wall in a stationary frame. While the compressor stalls, the stress at the blade root can be higher, which can provide valuable guidance for monitoring the lifecycle of compressor blades.

Modulation of optical force by adjusting the distance between three-layer photonic crystal slabs

Optical forces induced by polarization singularities from photonic crystal slabs (PCSs) have gained widely attention in recent years. To enhance the degree of freedom in controlling far-field optical forces, we propose and design a three-layer PCSs structure that simultaneously possesses multiple optical forces with reconfigurability. By modulating the interlayer spacing, the coupling strength between the slabs is regulated, resulting in a band transition from the nodal rings to the nodal ridge, which facilitates the generation of dual polarization vortices. These dual polarization vortices induce multiple phase singularities at their boundaries, leading to multiple optical force singularities, offering the possibility of capturing and dispersing nanoparticles. Interestingly, tuning the spacing among the slabs can transform the converging force into the diverging force at the center, therefore achieving particle screening. This work not only expands the application of nodal ridges to optical force in photonic structures but also provides a feasible approach for the generation of double-ring vortex beam in the nano-optics field.

Involuntary motor responses are elicited both by rare sounds and rare pitch changes

Unpredictable deviations from an otherwise regular auditory sequence, as well as rare sounds following a period of silence, are detected automatically. Recent evidence suggests that the latter also elicit quick involuntary modulations of ongoing motor activity emerging as early as 100 ms following sound onset, which was attributed to supramodal processing. We explored such force modulations for both rare and deviant sounds. Participants (N = 29) pinched a force sensitive device and maintained a force of 1–2 N for periods of 1 min. Task-irrelevant tones were presented under two conditions. In the Rare condition, 4000 Hz tones were presented every 8-to-16 s. In the Roving condition, 4000 Hz and 2996 Hz tones were presented at rate of 1 s, with infrequent (p = 1/12) frequency changes. In the Rare condition, transient force modulations were observed with a significant increase at ~ 234 ms, and a decrease at ~ 350 ms. In the Roving condition with low frequency deviant tones, an increase in force was observed at ~ 277 ms followed by a decrease at ~ 413 ms. No significant modulations were observed during perception of high frequency deviants. These results suggest that both rare silence-breaking sounds and low-pitched deviants evoke automatic fluctuations of motor responses, which opens up the possibility that these force modulations are triggered by stimulus-specific change-detection processes.

Fabrication and Temporal Dependency Osteogenic Regulation of Dual-Scale Hierarchical Microstructures on Medical Metal Surface.

The structural characteristics at the interface of bone implants can guide biological regulation. In this study, a dual-scale hierarchical microstructure is proposed and customized using hybrid machining to achieve temporal dependency osteogenic regulation. It is observed that osteoblasts induced by dual-scale hierarchical structure exhibit adequate protrusion development and rapid cell attachment through the modulation of mechanical forces in the cell growth environment, and further promot the upregulation of the cell membrane receptor PDGFR-α, which is related to cell proliferation. Afterward, transcriptomic analysis reveals that during the differentiation stage, the DSH structure regulates cellular signaling cascades primarily through integrin adhesion mechanisms and then accelerates osteogenic differentiation by activating the TGF-β pathway and cAMP signaling pathway. Furthermore, the calcium nodules are preferentially deposited within the lower honeycomb-like channels, thereby endowing the proposed dual-scale hierarchical structure with the potential to induce oriented deposition and improve the long-term stability of the implant.

Inter-Digit Low Level Force Coordination in a Complex Isometric Pinch Tracking Task

This study examined whether target pursuit tracking by a performer-controlled computer cursor around a square diamond-shaped circuit, using isometric pinch grip force production, would show a significant difference in performance metrics dependent on the clockwise sense of the target movement along the trajectory path. The target template incorporated path segments requiring all four possible combinations of directional force modulation patterns (increasing and decreasing isometric pinch forces of the thumb and index finger). Overall, it was found that cursor positional accuracy was greater during counterclockwise pursuit, that steadiness was greater during clockwise pursuit, and that the cursor bearing angle with respect to target movement was biased toward cursor positioning being within the interior of the trajectory circuit regardless of clockwise sense.

Fluctuation of fine motor skills throughout the menstrual cycle in women

The effect of the menstrual cycle on fine motor skills is unclear. This study determined whether the menstrual cycle affected fine motor skills and related neural activities. Nineteen women with regular menstrual cycles were tested for fine motor skills using two types of tasks: grooved pegboard task (GPT), which evaluates motor control with high freedom of movements, and force modulation task (FMT), which evaluates more complex and fine motor control with low freedom of movements. We also assessed primary motor cortex intracortical circuits and sensorimotor integration using paired-pulse transcranial magnetic stimulation to reveal why the menstrual cycle affects fine motor skills. The present study indicated that fine motor skills assessed by FMT varied throughout the menstrual cycle while those measured by GPT did not. These results suggest that fine motor skills requiring more complex and fine control may be affected by the menstrual cycle. Additionally, changes in fine motor skills throughout the menstrual cycle may be associated with the severity of menstruation-related symptoms.

An atomic force microscope-like dual-stage force controlled fast tool servo for in-process inspection of micro-structured surfaces

This study presents the development of a dual-stage force sensor integrated fast tool servo (FS-FTS) for in-process inspection of micro-structures. With the cutting tool serving as a probe, the measurement principle of the FS-FTS is similar to that of an atomic force microscope (AFM). The force modulation method, inspired by the tapping mode AFM, is employed to detect the weak contact between the cutting tool and the workpiece. The primary stage of the dual-stage FTS is responsible for tracking the surface profile of the micro-structures while the secondary stage offers the high-frequency oscillation to modulate the force signal. An experimental method is proposed to determine the optimal oscillation frequency. The transfer function of the FS-FTS, from the input voltage of the primary stage to the output force of the force detection module, is identified, and a notch filter integrated feedback controller is designed for the force control. With the designed dual-stage FS-FTS and force controller, the tip of the cutting tool could follow the unknown workpiece contour with a specified constant contact force, and the surface profile is obtained through the measured displacement of the primary stage. The feasibility and superiority of the developed system are validated through the in-process inspection of micro-lens with a depth of 19μm. The results demonstrate that the developed FS-FTS realizes the sub-micron profile measurement with a scanning speed of 150μm/min, and the depth of the resulting surface scratches is less than 20 nm.

Investigation of Eccentric PM on High-Frequency Vibration in FSCW PM Machine Considering Force Modulation Effect

Investigation of Eccentric PM on High-Frequency Vibration in FSCW PM Machine Considering Force Modulation Effect

Closed-loop optogenetic neuromodulation enables high-fidelity fatigue-resistant muscle control.

Closed-loop neuroprostheses show promise in restoring motion in individuals with neurological conditions. However, conventional activation strategies based on functional electrical stimulation (FES) fail to accurately modulate muscle force and exhibit rapid fatigue because of their unphysiological recruitment mechanism. Here, we present a closed-loop control framework that leverages physiological force modulation under functional optogenetic stimulation (FOS) to enable high-fidelity muscle control for extended periods of time (>60 minutes) in vivo. We first uncovered the force modulation characteristic of FOS, showing more physiological recruitment and significantly higher modulation ranges (>320%) compared with FES. Second, we developed a neuromuscular model that accurately describes the highly nonlinear dynamics of optogenetically stimulated muscle. Third, on the basis of the optogenetic model, we demonstrated real-time control of muscle force with improved performance and fatigue resistance compared with FES. This work lays the foundation for fatigue-resistant neuroprostheses and optogenetically controlled biohybrid robots with high-fidelity force modulation.

Pulsed Propulsion of Unmanned Aerial Vehicles by Centrifugal Force Modulation—First-Order Theory and Practicability

A novel technique suitable for the propulsion of small unmanned aerial vehicles (UAV) is discussed in this paper. This approach utilizes the rotational energy of airborne gyro rotors and converts it into translational propulsion for the vehicle. The energy conversion is achieved by generating precisely directed centrifugal force pulses through short-duration rotor unbalances. The accurate control of the timing and magnitude of these unbalances is crucial for successful propulsion generation. Our first-order theory of controlled unbalance propulsion (CUP) predicts the potential for achieving high translational accelerations and vehicle velocities up to orbital levels. Power-saving levitation of UAVs can be attained. In this paper, we provide traceable evidence that pulsed centrifugal propulsion is based on well-established laws of physics and can be realized using state-of-the-art technologies.

Morphological Study before and after Thermal Treatment of Polymer-Polymer Mixed-Matrix Membranes for Gas Separations.

A good integration of the polymer materials that form a mixed-matrix membrane (MMM) for gas separation is essential to reaching interesting permselective properties. In this work, a porous polymer network (PPN), obtained by combining triptycene and trifluoroacetophenone, has been used as a filler, which was blended with two o-hydroxypolyamides (HPAs) that act as polymer matrices. These polymer matrices have been thermally treated to induce a thermal rearrangement (TR) of the HPAs to polybenzoxazoles (β-TR-PBOs) through a solid-state reaction. For its structural study, various techniques have been proposed that allow us to undertake a morphological investigation into the integration of these materials. To access the internal structure of the MMMs, three different methods were used: a polishing process for the material surface, the partial dissolution of the polymer matrix, or argon plasma etching. The argon plasma technique has not only revealed its potential to visualize the internal structure of these materials; it has also been proven to allow for the transformation of their permselective properties. Force modulation and phase contrast in lift-mode techniques, along with the topographic images obtained via the tapping mode using a scanning probe microscope (SPM), have allowed us to study the distribution of the filler particles and the interaction of the polymer and the filler. The morphological information obtained via SPM, along with that of other more commonly used techniques (SEM, TGA, DSC, FTIR, WASX, gas adsorption, and permeability measurements), has allowed us to postulate the most probable structural configuration in this type of system.