Piezoelectric Energy Harvesting from Rotational Motion to Power Industrial Maintenance Sensors

In industry, forecasting machinery failures could save significant time and money if any maintenance breaks are predictable. The aim of this work was to develop an energy harvesting system which could, in theory, power condition monitoring sensors in heavy machinery. In this study, piezoelectric-cantilever-type energy harvesters were attached to a motor and spun around with different rotational speeds. A mass was placed on the tip of the cantilevers, which were mounted pointing inward toward the center axis of the motor. Pointing a cantilever tip inward and increasing the distance from the center axis of the motor decreased the natural resonance frequency significantly and thus enabled higher harvested energy levels with lower rotational frequencies. Motion of the cantilever was also controlled by altering the movement space of the tip mass. This created another possibility to control the cantilever dynamics and prevent overstressing of the piezoelectric material. Restricting the movement of the tip mass can also be used to harvest energy over a wider frequency range and prevent the harvester from getting trapped into a stagnant position. The highest calculated raw power of 579.2 µW at 7.4 Hz rotational frequency was measured from a cantilever with outer dimensions of 25 mm × 100 mm. Results suggest that an energy harvesting system with multiple cantilevers could be designed to replace batteries in condition sensors monitoring revolving machinery.

Recent Progress in Sensing Technology Based on Triboelectric Nanogenerators in Dynamic Behaviors

Under the trend of the rapid development of the internet of things (IoT), sensing for dynamic behaviors is widely needed in many fields such as traffic management, industrial production, medical treatment, building health monitoring, etc. Due to the feature of power supply independence and excellent working performance under a low-frequency environment, triboelectric nanogenerators (TENGs) as sensors are attracting more and more attention. In this paper, a comprehensive review focusing on the recent advance of TENGs as sensors for dynamic behaviors is conducted. The structure and material are two major factors affecting the performance of sensors. Different structure designs are proposed to make the sensor suitable for different sensing occasions and improve the working performance of the sensors. As for materials, new materials with stronger abilities to gain or lose electrons are fabricated to obtain higher surface charge density. Improving the surface roughness of material by surface engineering techniques is another strategy to improve the output performance of TENG. Based on the advancement of TENG structures and materials, plenty of applications of TENG-based sensors have been developed such as city traffic management, human-computer interaction, health monitoring of infrastructure, etc. It is believed that TENG-based sensors will be gradually commercialized and become the mainstream sensors for dynamic sensing.

Theoretical and Experimental Investigation of a Rotational Magnetic Couple Piezoelectric Energy Harvester

With the rapid development of Internet of Things (IoT) and the popularity of wireless sensors, using internal permanent or rechargeable batteries as a power source will face a higher maintenance workload. Therefore, self-powered wireless sensors through environmental energy harvesting are becoming an important development trend. Among the many studies of energy harvesting, the research on rotational energy harvesting still has many shortcomings, such as rarely working effectively under low-frequency rotational motion or working in a narrow frequency band. In this article, a rotational magnetic couple piezoelectric energy harvester is proposed. Under the low-frequency excitation (<10 Hz) condition, the harvester can convert low-frequency rotational into high-frequency vibrational of the piezoelectric beam by frequency up-conversion, effectively increasing the working bandwidth (0.5−16 Hz) and improving the efficiency of low-speed rotational energy harvesting. In addition, when the excitation frequency is too high (>16 Hz), it can solve the condition that the piezoelectric beam cannot respond in time by frequency down-conversion. Therefore, the energy harvester still has a certain degree of energy harvesting ability (18−22 Hz and 29−31 Hz) under high-frequency conditions. Meanwhile, corresponding theoretical analyses and experimental verifications were carried out to investigate the dynamic characteristics of the harvester with different excitation and installation directions. The experimental results illustrate that the proposed energy harvester has a wider working bandwidth benefiting from the frequency up-conversion mechanism and frequency down-conversion mechanism. In addition, the forward beam will have a wider bandwidth than the inverse beam due to the softening effect. In addition, the maximum powers of the forward and inverse beams at 310 rpm (15.5 Hz) are 93.8 μW and 58.5 μW, respectively. The maximum powers of the two beams at 420 rpm (21 Hz) reached 177 μW and 85.2 μW, respectively. The self-powered requirement of micromechanical systems can be achieved. Furthermore, this study provides the theoretical and experimental basis for rotational energy harvesting.

A Light-Powered Triboelectric Nanogenerator Based on the Photothermal Marangoni Effect

The photothermal Marangoni effect enables direct light-to-work conversion, which is significant for realizing the self-propulsion of objects in a noncontact, controllable, and continuous manner. Many promising applications have been demonstrated in micro- and nanomachines, light-driven actuators, cargo transport, and gear transmission. Currently, the related studies about photothermal Marangoni effect-induced self-propulsion, especially rotational motions, remain focused on developing the novel photothermal materials, the structural designs, and the controllable self-propulsion modes. However, extending the related research from the laboratory practice to practical application remains a challenge. Herein, we combined the photothermal Marangoni effect-induced self-propulsion with the triboelectric nanogenerator technology for sunlight intensity determination. Photothermal black silicon, superhydrophobic copper foam with drag-reducing property, and triboelectric polytetrafluoroethylene film were integrated to fabricate a triboelectric nanogenerator. The photothermal-Marangoni-driven triboelectric nanogenerator (PMD-TENG) utilizes the photothermal Marangoni effect-induced self-propulsion to realize the relative motion between the triboelectric layer and the electrode, converting light into electrical signals, with a peak value of 2.35 V. The period of the output electrical signal has an excellent linear relationship with the light intensity. The accessible electrical signal generation strategy proposed here provides a new application for the photothermal Marangoni effect, which could further inspire the practical applications of the self-powered system based on the photothermal Marangoni effect, such as intelligent farming.

Multi-Compartment Lymph-Node-on-a-Chip Enables Measurement of Immune Cell Motility in Response to Drugs

Organs On-a-Chip represent novel platforms for modelling human physiology and disease. The lymph node (LN) is a relevant immune organ in which B and T lymphocytes are spatially organized in a complex architecture, and it is the place where the immune response initiates. The present study addresses the utility of a recently designed LN-on-a-chip to dissect and understand the effect of drugs delivered to cells in a fluidic multicellular 3D setting that mimics the human LN. To do so, we analyzed the motility and viability of human B and T cells exposed to hydroxychloroquine (HCQ). We show that the innovative LN platform, which operates at a microscale level, allows real-time monitoring of co-cultured B and T cells by imaging, and supports cellular random movement. HCQ delivered to cells through a constant and continuous flow induces a reduction in T cell velocity while promotes persistent rotational motion. We also find that HCQ increases the production of reactive oxygen species in T cells. Taken together, these results highlight the potential of the LN-on-a-chip to be applied in drug screening and development, and in cellular dynamics studies.

Smallest Chimeras Under Repulsive Interactions

We present an exemplary system of three identical oscillators in a ring interacting repulsively to show up chimera patterns. The dynamics of individual oscillators is governed by the superconducting Josephson junction. Surprisingly, the repulsive interactions can only establish a symmetry of complete synchrony in the ring, which is broken with increasing repulsive interactions when the junctions pass through serials of asynchronous states (periodic and chaotic) but finally emerge into chimera states. The chimera pattern first appears in chaotic rotational motion of the three junctions when two junctions evolve coherently, while the third junction is incoherent. For larger repulsive coupling, the junctions evolve into another chimera pattern in a periodic state when two junctions remain coherent in rotational motion and one junction transits to incoherent librational motion. This chimera pattern is sensitive to initial conditions in the sense that the chimera state flips to another pattern when two junctions switch to coherent librational motion and the third junction remains in rotational motion, but incoherent. The chimera patterns are detected by using partial and global error functions of the junctions, while the librational and rotational motions are identified by a libration index. All the collective states, complete synchrony, desynchronization, and two chimera patterns are delineated in a parameter plane of the ring of junctions, where the boundaries of complete synchrony are demarcated by using the master stability function.

Experimental evaluation of the dosimetric impact of intrafraction prostate rotation using film measurement with a 6DoF robotic arm

PURPOSE

Tumor motion during radiotherapy can cause a reduction in target dose coverage and an increase in healthy tissue exposure. Tumor motion is not strictly translational and often exhibits complex six degree-of-freedom (6DoF) translational and rotational motion. Although the dosimetric impact of prostate tumor translational motion is well investigated, the dosimetric impact of 6DoF motion has only been studied with simulations or dose reconstruction. This study aims to experimentally quantify the dose error caused by 6DoF motion. The experiment was designed to test the hypothesis that 6DoF motion would cause larger dose errors than translational motion alone through gamma analyses of two-dimensional film measurements.

METHODS

Four patient-measured intrafraction prostate motion traces and four VMAT 7.25 Gy/Fx SBRT treatment plans were selected for the experiment. The traces represented typical motion patterns, including small-angle rotations (<4°), transient movement, persistent excursion, and erratic rotations (>6°). Gafchromic film was placed inside a custom-designed phantom, held by a high-precision 6DoF robotic arm for dose measurements in the coronal plane during treatment delivery. For each combination of the motion trace and treatment plan, two film measurements were made, one with 6DoF motion and the other with the three-dimensional (3D) translation components of the same trace. A gamma pass rate criteria of 2% relative dose/2 mm distance-to-agreement was used in this study and evaluated for each measurement with respect to the static reference film. Two test thresholds, 90% and 50% of the reference dose, were applied to investigate the difference in dose coverage for the PTV region and surrounding areas, respectively. The hypothesis was tested using a Wilcoxon signed-rank test.

RESULTS

For each of the 16 plan and motion trace pairs, a reduction in the gamma pass rate was observed for 6DoF motion compared with 3D translational motion. With 90% gamma-test threshold, the reduction was 5.8% ± 7.1% (P < 0.01). With 50% gamma-test threshold, the reduction was 4.1% ± 4.8% (P < 0.01).

CONCLUSION

For the first time, the dosimetric impact of intrafraction prostate rotation during SBRT treatment was measured experimentally. The experimental results support the hypothesis that 6DoF tumor motion causes higher dose error than translation motion alone.

Analysis of a Cantilevered Piezoelectric Energy Harvester in Different Orientations for Rotational Motion

This paper investigates a piezoelectric energy harvester that consists of a piezoelectric cantilever and a tip mass for horizontal rotational motion. Rotational motion results in centrifugal force, which causes the axial load on the beam and alters the resonant frequency of the system. The piezoelectric energy harvester is installed on a rotational hub in three orientations—inward, outward, and tilted configurations—to examine their influence on the performance of the harvester. The theoretical model of the piezoelectric energy harvester is developed to explain the dynamics of the system and experiments are conducted to validate the model. Theoretical and experimental studies are presented with various tilt angles and distances between the harvester and the rotating center. The results show that the installation distance and the tilt angle can be used to adjust the resonant frequency of the system to match the excitation frequency.

A Light-Driven Microgel Rotor

The current understanding of motility through body shape deformation of micro-organisms and the knowledge of fluid flows at the microscale provides ample examples for mimicry and design of soft microrobots. In this work, a 2D spiral is presented that is capable of rotating by non-reciprocal curling deformations. The body of the microswimmer is a ribbon consisting of a thermoresponsive hydrogel bilayer with embedded plasmonic gold nanorods. Such a system allows fast local photothermal heating and nonreciprocal bending deformation of the hydrogel bilayer under nonequilibrium conditions. It is shown that the spiral acts as a spring capable of large deformations thanks to its low stiffness, which is tunable by the swelling degree of the hydrogel and the temperature. Tethering the ribbon to a freely rotating microsphere enables rotational motion of the spiral by stroboscopic irradiation. The efficiency of the rotor is estimated using resistive force theory for Stokes flow. This research demonstrates microscopic locomotion by the shape change of a spiral and may find applications in the field of microfluidics, or soft microrobotics.

Illusory Oscillation of the Central Rotation Axis

In this study, we report a novel visual illusion for rotational motion, in which the central rotation axis of a partially invisible (apparent) square is perceived as exhibiting oscillatory rotation. To investigate the cause of this illusion, we measured the central position of a static apparent shape using an adjustment method (Experiment 1) and manipulated the speed of the rotating apparent square to test whether the illusion could be cancelled out by counteracting rotation using a constant method (Experiment 2). The results revealed that the perceived central position of a static apparent shape was shifted toward the outside. The shifted position depended on the orientation of the stimulus, and its position was arranged as if it was moving in a circular trajectory. In addition, the cancellation technique using counteracting rotation was successful, and cancellation of faster rotation required a greater radius of counteracting rotation. These results indicated that the illusion is induced by an interaction between illusory shifts of the central position of the static shape and the summation of motion vectors or motion momentum (e.g., centrifugal force) derived from shape representation by perceptual completion.

Three-dimensional global acceleration estimation in the presence of rotation using an inertial measurement unit for whole-body vibration studies

Off-road vehicle operators are likely exposed to not only a high level but also different types of whole-body vibration (WBV) such as significant non-vertical and/or rotational accelerations. To evaluate the effects of these different WBV exposures, it is necessary to first correctly estimate the acceleration of the vehicle considering not only translational but also rotational motion. The main objective of this study was to propose and evaluate an algorithm to accurately estimate global acceleration of a vehicle using magnitude-based filtering and inertial navigation with an inertial measurement unit. In a laboratory experiment where a 6-df robotic arm generated three-dimensional motion at three different frequencies (2.3, 4.5 and 8.5 Hz), local acceleration data were collected in the presence of rotational movements. The comparison of the calculated global acceleration to the reference data show that the algorithm provides a good estimation of global acceleration even when rotational movement is not negligible.

Parameter Estimation of Micro-Motion Targets for High-Resolution-Range Radar Using Online Measured Reference

Micro-motion dynamics produce Micro-range (m-R) signatures which are important features for target classification and recognition, provided that the range resolution of radar signal is high enough. However, dechirping the echo with reference measured by narrow bandwidth radar would generate the residual translational motion, which exhibits as random shifts of envelopes of range profiles. The residual translational motion would destroy the periodicity of m-R signatures and make a challenge to estimate rotational parameter. In this work, we proposed an efficient high-resolution range profile (HRRP)-based method to estimate rotational parameter, in which online measured reference distances are used to dechirp the radar raw echo. Firstly, the deduction for the modified first conditional comment of range profiles (MFCMRP) is introduced in detail, and the MFCMRP contain periodic and random components when dechirped by measured reference, corresponding to the rotational motion and the reference measured errors compared with actual reference. Secondly, the Wavelet Transform (WT) is utilized to separate the measured errors from the MFCMRP. The estimations of measured errors are used to compensate the MFCMRP, and then autocorrelation is performed on the estimated periodic component to obtain the estimation of rotational period. Lastly, the rotational amplitudes and phases are achieved by inverse Radon transform (IRT) of the compensated HRRP. The effectiveness of the proposed method in this paper is verified by synthetic data and measured radar data.

Semicircular canal modeling in human perception

The human vestibular system is a sensory and equilibrium system that manages and controls the human sense of balance and movement. It is the main sensor humans use to perceive rotational and linear motions. Determining an accurate mathematical model of the human vestibular system is significant for research pertaining to motion perception, as the quality and effectiveness of the motion cueing algorithm (MCA) directly depends on the mathematical model used in its design. This paper describes the history and analyses the development process of mathematical semicircular canal models. The aim of this review is to determine the most consistent and reliable mathematical semicircular canal models that agree with experimental results and theoretical analyses, and offer reliable approximations for the semicircular canal functions based on the existing studies. Selecting and formulating accurate mathematical models of semicircular canals are essential for implementation into the MCA and for ensuring effective human motion perception modeling.

Self-Propelled Metal-Polymer Hybrid Micromachines with Bending and Rotational Motions

Two self-propelled micromachines were fabricated with gold/platinum micromotors that exhibit simple translational motion in a fuel solution. In each one, two micromotors were connected with a joint of polymer tube formed by stacking cationic poly(allylamine hydrochloride) (PAH) and anionic poly(acrylic acid) (PAA) using a layer-by-layer technique. A bent structure was created by making one longitudinal side of the joint more swellable with alkaline treatment. The joint containing fewer PAA/PAH bilayers was flexible and allowed a larger range of Brownian angular fluctuation. In the fuel solution, bending and stable rotation were observed for the micromotors tethered with soft and rigid angled joints, respectively. The radius and angular velocity of the rotation depended on the angle of the joint. Such tethered micromotors can be used to realize sophisticated micro/nanomachines for microscale surgery and drug delivery.

Elongation factor G initiates translocation through a power stroke

During the translocation step of prokaryotic protein synthesis, elongation factor G (EF-G), a guanosine triphosphatase (GTPase), binds to the ribosomal PRE-translocation (PRE) complex and facilitates movement of transfer RNAs (tRNAs) and messenger RNA (mRNA) by one codon. Energy liberated by EF-G's GTPase activity is necessary for EF-G to catalyze rapid and precise translocation. Whether this energy is used mainly to drive movements of the tRNAs and mRNA or to foster EF-G dissociation from the ribosome after translocation has been a long-lasting debate. Free EF-G, not bound to the ribosome, adopts quite different structures in its GTP and GDP forms. Structures of EF-G on the ribosome have been visualized at various intermediate steps along the translocation pathway, using antibiotics and nonhydolyzable GTP analogs to block translocation and to prolong the dwell time of EF-G on the ribosome. However, the structural dynamics of EF-G bound to the ribosome have not yet been described during normal, uninhibited translocation. Here, we report the rotational motions of EF-G domains during normal translocation detected by single-molecule polarized total internal reflection fluorescence (polTIRF) microscopy. Our study shows that EF-G has a small (∼10°) global rotational motion relative to the ribosome after GTP hydrolysis that exerts a force to unlock the ribosome. This is followed by a larger rotation within domain III of EF-G before its dissociation from the ribosome.

Differential contribution of visual and auditory information to accurately predict the direction and rotational motion of a visual stimulus

Vision and auditory information are critical for perception and to enhance the ability of an individual to respond accurately to a stimulus. However, it is unknown whether visual and auditory information contribute differentially to identify the direction and rotational motion of the stimulus. The purpose of this study was to determine the ability of an individual to accurately predict the direction and rotational motion of the stimulus based on visual and auditory information. In this study, we recruited 9 expert table-tennis players and used table-tennis service as our experimental model. Participants watched recorded services with different levels of visual and auditory information. The goal was to anticipate the direction of the service (left or right) and the rotational motion of service (topspin, sidespin, or cut). We recorded their responses and quantified the following outcomes: (i) directional accuracy and (ii) rotational motion accuracy. The response accuracy was the accurate predictions relative to the total number of trials. The ability of the participants to predict the direction of the service accurately increased with additional visual information but not with auditory information. In contrast, the ability of the participants to predict the rotational motion of the service accurately increased with the addition of auditory information to visual information but not with additional visual information alone. In conclusion, this finding demonstrates that visual information enhances the ability of an individual to accurately predict the direction of the stimulus, whereas additional auditory information enhances the ability of an individual to accurately predict the rotational motion of stimulus.

Is macrocycle a synonym for kinetic inertness in Gd(III) Complexes? Effect of coordinating and noncoordinating substituents on inertness and relaxivity of Gd(III) chelates with DO3A-like ligands

Gadolinium chelates with octadentate ligands are widely used as contrast agents for magnetic resonance imaging (MRI), with macrocyclic ligands based on DO3A being preferred for the high kinetic inertness of their Gd chelates. A major challenge in the design of new bifunctional MRI probes is the need to control the rotational motion of the chelate, which greatly affects its relaxivity. In this work we explored facile alkylation of a secondary amine in macrocyclic DO3A-like ligands to create a short, achiral linkage to limit the undesired internal motion of chelates within larger molecular constructs. The acetate moiety on the trans nitrogen was also replaced with either a bidentate (ethoxyacetate, L1 or methyl picolinate, L2) or bulky monodentate (methyl phosphonate, L3) donor arm to give octa- or heptadentate ligands, respectively. The resultant Gd(III) complexes were all monohydrated (q = 1) and exhibited water residency times that spanned 2 orders of magnitude (τM = 2190 ± 170, 3500 ± 90, and 12.7 ± 3.8 ns at 37 °C for GdL1, GdL2, and GdL3, respectively). Alkylation of the secondary amine with a noncoordinating biphenyl moiety resulted in coordinatively saturated q = 0 complexes of octadentate ligands L1 and L2. Relaxivities were limited by slow water exchange and/or lack of water coligand. All complexes showed decreased inertness compared to [Gd(DO3A)] despite higher ligand denticity, and inertness was further decreased upon N-alkylation. These results demonstrate that high kinetic inertness and in vivo safety of Gd chelates with macrocyclic ligands should not be generalized.

Comparison of shoulder range of motion, strength, and playing time in uninjured high school baseball pitchers who reside in warm- and cold-weather climates

BACKGROUND

There is an assumption that baseball athletes who reside in warm-weather climates experience larger magnitude adaptations in throwing shoulder motion and strength compared with their peers who reside in cold-weather climates.

HYPOTHESES

(1) The warm-weather climate (WWC) group would exhibit more pronounced shoulder motion and strength adaptations than the cold-weather climate (CWC) group, and (2) the WWC group would participate in pitching activities for a greater proportion of the year than the CWC group, with the time spent pitching predicting throwing shoulder motion and strength in both groups.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

One hundred uninjured high school pitchers (50 each WWC, CWC) were recruited. Rotational shoulder motion and isometric strength were measured and participants reported the number of months per year they pitched. To identify differences between groups, t tests were performed; linear regression was used to determine the influence of pitching volume on shoulder motion and strength.

RESULTS

The WWC group pitched more months per year than athletes from the CWC group, with the number of months spent pitching negatively related to internal rotation motion and external rotation strength. The WWC group exhibited greater shoulder range of motion in all planes compared with the CWC group, as well as significantly lower external rotation strength and external/internal rotation strength ratios. There was no difference in internal rotation strength between groups, nor a difference in the magnitude of side-to-side differences for strength or motion measures.

CONCLUSION

Athletes who reside in cold- and warm-weather climates exhibit differences in throwing shoulder motion and strength, related in part to the number of months spent participating in pitching activities. The amount of time spent participating in pitching activities and the magnitude of range of motion and strength adaptations in athletes who reside in warm-weather climates may make these athletes more susceptible to throwing-related injuries.

Tympanic-membrane and malleus-incus-complex co-adaptations for high-frequency hearing in mammals

The development of the unique capacity for high-frequency hearing in many mammals was due in part to changes in the middle ear, such as the evolution of three distinct middle-ear bones and distinct radial and circumferential collagen fiber layers in the eardrum. Ossicular moment(s) of inertia (MOI) and principal rotational axes, as well as eardrum surface areas, were calculated from micro-CT-based 3-D reconstructions of human, cat, chinchilla, and guinea pig temporal bones. For guinea pig and chinchilla, the fused malleus-incus complex rotates about an anterior-posterior axis, due to the relatively lightweight ossicles and bilateral symmetry of the eardrum. For human and cat, however, the MOI calculated for the unfused malleus are 5-6 times smaller for rotations about an inferior-superior axis than for rotations about the other two orthogonal axes. It is argued that these preferred motions, along with the presence of a mobile malleus-incus joint and asymmetric eardrum, enable efficient high-frequency sound transmission in spite of the relatively large ossicular masses of these species. This work argues that the upper-frequency hearing limit of a given mammalian species can in part be understood in terms of morphological co-adaptations of the eardrum and ossicular chain.