Rigid Components Research Articles

Bio-inspired “rigid and flexible” structure design for robust superhydrophobic composite and its application

The mechano-chemical-physical robustness is essential for the practical applications of a superhydrophobic coating. However, the superhydrophobic coatings obtained following general design principles hold inherent vulnerability. In this work, inspired by the pangolins’ combination of the rigid armour and the flexible flesh, we propose a new universal “rigid and flexible” design strategy for preparing a superhydrophobic coating with intrinsic mechano-chemical-physical robustness by introducing both rigid and flexible components. As a proof-of-concept, a robust superhydrophobic “rigid and flexible” coating is fabricated using rigid corundum particles and flexible rubber particles. In our design, the rigid component (i.e. corundum particles) provides the protection for the entire structure from mechanical wear, while the flexible component (i.e. rubber particles) endows the structure excellent deformability to eliminate stress under impact, thus having a synergistical advantage in adapting to various mechanical destructions. The as-obtained superhydrophobic “rigid and flexible” coating show superior mechano-chemical-physical robustness against various harsh conditions including 1200 cycles of 2 Kg (40 KPa) linear abrasion, tape-peeling, knife-scratching, water-jetting and chemical corrosion. In addition, the “rigid and flexible” superhydrophobic coating exhibits an excellent weathering resistance and anti-icing properties. Our “rigid and flexible” design strategy will provide a new insight for the development of robust superhydrophobic materials and broaden its application scenarios.

(Invited) smart Wearable Electronics for Chronic Disease Management

60% of Americans live with at least one chronic disease. These diseases and associated comorbidities are now the leading causes of death in the United States. Effective management of complex chronic diseases requires body-wide, long-term, accurate, and continuous monitoring of multiple physiological signals from wearable devices to precisely determine the pathological state. These wearable physiological signal monitoring can dramatically reduce the demand of physician visiting and increase patients’ engagement and treatment adherence rate. Although wearable bioelectronic devices have shown huge potential in chronic disease management, existing technology still mostly relies on rigid chip components, where the interface between chips and skin/tissue has been a bottleneck that limits the system performance (noise, robustness etc). To address these challenges, my research has been involved in the exploration of rational system design concepts, material and device fabrication innovation, and tailored algorithms to enable smart wearable electronics that targets next-generation chronic disease management.Here I would like to discuss two of my developed technology platforms to elaborate the concept of smart wearables. First, I will describe a body area sensor network technology platform. In the system design concept side, this technology utilizes a novel wireless hybridization strategy and an unconventional detuned RFID working regime that provide an ideal skin interface. In the material/device side, this system integrates several skin-conforming polymer-based soft devices (ring oscillators, RF diodes, antennas, transistors etc.) as an integrated soft multimode sensing sticker. (1,2) Next, I will describe a wireless closed-loop smart bandage that can accelerate and monitor the wound healing process. (3) Such smart bandage also integrates new design concepts (wireless, battery-free design that combines both sensing and stimulation), novel materials (low-impedance, high-toughness, and tunable adhesion hydrogel as skin interface) and closed-loop control algorithms. Overall, the developed technology platform could assess multiple health outcomes and treatment responses to various chronic diseases. Ultimately, this technology will help to reduce chronic disease burden, lower medical costs, and provide a better quality of life for patients.

Liquid‐Metal/Nd2Fe14B/Ecoflex Composite Soft Robots and Their Electric Signal Transmission using Non‐Contact Tentacles

AbstractSignal transmission between rigid robots is usually realized through rigid electronic components like coil or circuit board. However, these rigid electronic units are difficult to be used in fully flexible soft robots because of the mismatch of Young's modulus. Liquid metal (LM), as a flexible fluid with superior electric conductivity, can be served as the alternative material for rigid electronic units to realize signal transmission in fully flexible soft robots. Herein, a fully flexible soft robot is fabricated, which is mainly consists of two functional units: the soft tentacle integrated with liquid metal spiral wire and the body prepared by Nd2Fe14B magnetic powders/Ecoflex composites. The fully flexible soft robot can not only transmit electric signals based on electromagnetic induction but also be actuated by an external magnetic field to form diverse signal transmission pathways. Related mechanisms of transmitting electric signal and driving are studied by Maxwell numerical simulation. Driven by an external magnetic field, three soft robots are capable to constitute two different pathways to transmit electric signals to the oscilloscope. It is believed that the integration of LM into the magnetic composites provides an open perspective to realize the signal transmission in fully flexible soft robot and favors the development of multifunctional soft robot.

Dynamic Analysis and Numerical Simulation of Arresting Hook Engaging Cable in Carried-Based UAV Landing Process

Carrier-based unmanned aerial vehicles (UAVs) require precise evaluation methods for their landing and arresting safety due to their high autonomy and demanding reliability requirements. In this paper, an efficient and accurate simulation method is presented for studying the arresting hook engaging arresting cable process. The finite element method and multibody dynamics (FEM-MBD) approach is employed. By establishing a rigid–flexible coupling model encompassing the UAV and arresting gear system, the simulation model for the engagement process is obtained. The model incorporates multiple coordinate systems to effectively capture the relative motion between the rigid and flexible components. The model considers the material properties, arresting gear system characteristics, and UAV state during engagement. Verification is conducted by comparing simulation results with experimental data from a referenced arresting hook rebound. Finally, simulations are performed under different touchdown points and roll angles of the UAV to analyze the stress distribution of the hook, center of gravity variations, and the tire touch and rollover cable response. The proposed rigid–flexible coupling arresting dynamics model in this paper enables the effective analysis of the dynamic behavior during the arresting hook engaging arresting cable process.

Bionic threshing component optimized based on MBD-DEM coupling simulation significantly improves corn kernel harvesting rate

The most widely used rigid threshing component (RTC) currently has a constant problem with high kernel damage rates. Inspired by the seldom occurrence of kernel damage in manual threshing operations, this study designed a bionic threshing component (BTC) by using the human thumb as a bionic prototype. BTC can imitate the thumb's real-time profiling capability on the shape of the corn ears, thereby reproducing the thumb's “flexible profiling impact“ method of applying force, significantly different from the “rigid impact method” of RTC. Based on EDEM and RecurDyn software, the MBD-DEM coupling simulation model of the threshing operation was constructed. Through the coupling simulation experiments, the influence law of the BTC core design parameter k (bionic joint torque elasticity coefficient) on the kernel harvesting rate η, threshing rate and damage rate was revealed. Meanwhile, the optimum value of k (2.08 KN·mm/°) was derived by modelling the k-η regression. Bench comparison and simulation accuracy verification experiments showed that BTC operated with optimal k values can increase corn kernel harvesting rates by 0.87%–1.57%, compared to RTC. (BTC was able to achieve the highest kernel harvesting and threshing rates of 98.61% and 98.97%, respectively, with breakage rates as low as 0.16%). Meanwhile, the computational results of the MBD-DEM coupling simulation model established in this study were not significantly difference from the bench experiment (P > 0.05). To sum up, this study can provide a new mechanism design idea and parameter optimization method for the development of threshing components.

Effect of surfactants on the interfacial behaviors of diacylglycerol-based solid lipid nanoparticles and physical stability of W/O emulsion

The influence of surfactants (Span 80, Span 60, PGPR and sodium caseinate) on the stability of W/O emulsions stabilized by diacylglycerol (DAG)-based solid Lipid nanoparticles (SLN) was investigated. DAG-based SLN showed phase separation at high NaCl concentration and acidic pH although the SLN-stabilized W/O emulsion was minimally affected. Span 80 increased the hydrophobicity whereas Span 60 increased the hydrophilicity of SLN. With concentration close to CMC, both Span surfactants caused detachment of SLN from interface and reduced emulsion stability. Nonetheless, addition of a small amount (0.1 wt%) of Span surfactants increased the interfacial modulus. The co-adsorption of SLN and PGPR at the oil-water interface promoted the formation of denser network structure and higher interfacial elasticity, which enhanced the emulsion rigidity and freeze-thaw stability. Sodium caseinate (NaCAS) showed intense competition with particles for adsorption at the interface and caused emulsion destabilization. Consequently, the NaCl release rate was directly influenced by the emulsion stability and the interaction between surfactants with SLN. The results have important implications for applying DAG nanoparticles as stabilizers in W/O emulsions with tailoring interfacial rigidity and water-soluble component release behaviors.

A Tensegrity Joint for Low‐Inertia, Compact, and Compliant Soft Manipulators

Compact, low‐inertia, and soft compliant robotic joint mechanisms are in great demand for ensuring safe interactions in human–robot collaborative tasks. Tensegrity, of which the structural integrity is constrained by tension, does not involve static/sliding friction among the rigid components. However, this mechanical stability is very susceptible to actuation errors. It requires complex kinematics modeling and sophisticated control model with sensing feedback. Herein, a low‐inertia tensegrity joint that is covered/protected by a fiber Bragg grating (FBG)‐embedded silicone sheath is proposed, with the aim to reinforce the joint motion stability and enable self‐contained sensing feedback. A learning‐based closed‐loop controller is also designed and trained with the proper joint configurations selected by a two‐step sampling method. Both the kinematics and static equilibriums of such configurations can be well satisfied. The experiments demonstrate that the joint can follow paths accurately in 2D by compensating manipulation error shortly under the closed‐loop control. The joint stiffness can also be varied against the external/impulsive disturbances. It can be foreseen that this primitive robot joint component with 2 degrees of freedom (DoFs) can provide safe, compliant interaction with human, for which a simple test of maneuvering a portable ultrasound probe (≈210 g) for abdominal imaging is demonstrated.

Research Progress in Stretchable Circuits: Materials, Methods, and Applications

AbstractStretchable electronic devices, with their excellent properties such as stretchability and conformal contact with complex surfaces, are widely used in health monitoring and human‐computer interactions. For stable operation of these devices, stretchable circuits are crucial, enabling integration of sensors, data collection, and transmission while under strain. To achieve stretchable system integration, addressing key issues such as elastic substrates, sensor devices, rigid components, stretchable electrodes, and packaging layers is necessary. The stretchable electrodes, which connect various functional devices, are crucial for achieving stretchability and are the main focus of this review. Firstly, this work explores the enhancement of electrode design to maintain good electrical conductivity even under stretching conditions, through studying stretchable conductive materials and the structural design of conventional materials. This work then presents studies on substrate interfaces and the design of elastic substrates, such as rigid islands, to enhance the stability of stretchable circuits during use. Finally, the article discusses the applications of stretchable circuits, the challenges they face, and provides new research directions and ways to develop stretchable circuits.

Liquid Metal Fibers with a Knitted Structure for Wearable Electronics.

Flexible conductive fibers have shown tremendous potential in diverse fields, including health monitoring, intelligent robotics, and human-machine interaction. Nevertheless, most conventional flexible conductive materials face challenges in meeting the high conductivity and stretchability requirements. In this study, we introduce a knitted structure of liquid metal conductive fibers. The knitted structure of liquid metal fiber significantly reduces the resistance variation under tension and exhibits favorable durability, as evidenced by the results of cyclic tensile testing, which indicate that their resistance only undergoes a slight increase (<3%) after 1300 cycles. Furthermore, we demonstrate the integration of these liquid metal fibers with various rigid electronic components, thereby facilitating the production of pliable LED arrays and intelligent garments for electrocardiogram (ECG) monitoring. The LED array underwent a 30 min machine wash, during which it consistently retained its normal functionality. These findings evince the devices' robust stable circuit functionality and water resistance that remain unaffected by daily human activities. The liquid metal knitted fibers offer great promise for advancing the field of flexible conductive fibers. Their exceptional electrical and mechanical properties, combined with compatibility with existing electronic components, open new possibilities for applications in the physiological signal detection of carriers, human-machine interaction, and large-area electronic skin.

A soft, self-sensing tensile valve for perceptive soft robots

Soft inflatable robots are a promising paradigm for applications that benefit from their inherent safety and adaptability. However, for perception, complex connections of rigid electronics both in hardware and software remain the mainstay. Although recent efforts have created soft analogs of individual rigid components, the integration of sensing and control systems is challenging to achieve without compromising the complete softness, form factor, or capabilities. Here, we report a soft self-sensing tensile valve that integrates the functional capabilities of sensors and control valves to directly transform applied tensile strain into distinctive steady-state output pressure states using only a single, constant pressure source. By harnessing a unique mechanism, “helical pinching”, we derive physical sharing of both sensing and control valve structures, achieving all-in-one integration in a compact form factor. We demonstrate programmability and applicability of our platform, illustrating a pathway towards fully soft, electronics-free, untethered, and autonomous robotic systems.

Non-linear Wire Rope Isolator Model to Enhance Transportation Simulation of Fragile Equipment

IntroductionWire rope isolators are often used as means of vibration isolation for the transportation of fragile machine equipment. When deployed as suspension systems in a transportation scenario, a simple spring–damper model is often used to predict the dynamic loads that act on the structure being transported. However, this simple model has proved to be too simplistic to be used in the development of an accurate numerical model that can predict the vibration levels experienced by the inner components of fragile equipment during its transportation. This paper describes the experimental tests conducted on a wire rope isolator used for the transportation of the prototype SSR1 cryomodule.Materials and methodsA hysteretic Bouc–Wen model has been used to analytically describe the force–deformation relationship of the wire rope isolators. The developed model of the isolator has been implemented in a larger model to simulate the actual transportation of the prototype SSR1 cryomodule, a section of the new PIP-II linear accelerator under construction at Fermilab. A series of multibody dynamic simulations with rigid and flexible components was used to numerically determine the acceleration of some critical components.Results and conclusionsAn actual experimental transportation was simulated using two numerical models: the developed Bouc–Wen model and a conventional spring–damper model. It is shown how the Bouc–Wen formulation of the isolator characteristics drastically improves the correspondence between experimental and simulated results if compared to a spring–damper model, especially in the range of 0–30 Hz which is the most critical for transportation problems.

Preparation and characterization of low CTE thermoplastic copolyimide resins based on the structural design of block sequence

In order to solve the challenge of balancing the thermoplastic processing properties and thermal dimensional stability of polyimide (PI) resin, in this research, 3,3′,4,4′-biphenyl tetracarboxylic diandhydride (BPDA) and 2,2′-bis(trifluoromethyl)benzidine (TFMB) were used as rigid components, 4,4′-oxydiphthalic anhydride (ODPA) and 4,4′-diaminodiphenyl sulfone (DDS) as flexible components. A series of random copolyimide resins was prepared by adjusting the molar ratio of rigid and flexible monomers. Determining the molar ratio which could balance the thermoplastic processing properties and thermal dimensional stability, block copolyimide resins with different rigid and flexible block lengths were then prepared in this ratio. The research showed that the molar ratio of monomers and the sequence structure of molecular chains had a strong influence on the performance of PI resins. When the content or block length of rigid component increased, the coefficient of thermal expansion (CTE) decreased but the glass transition temperatures (Tg) and melt viscosity increased. The PI-B343 resin had a CTE value of 40.63 ppm/K and the lowest melt viscosity reached 675 Pa·s, achieved the simultaneous regulation of the thermoplastic processing properties and thermal dimensional stability for PI resin.

One-pot ternary sequential reactions for photopatterned gradient multimaterials

One-pot ternary sequential reactions for photopatterned gradient multimaterials

GPART: Partitioning Maximal Redundant Rigid and Maximal Global Rigid Components in Generic Distance Graphs

Partitioning the Maximal Redundant Rigid Components (MRRC) and Maximal Global Rigid Components (MGRC) in generic 2D graphs are critical problem for network structure analysis, network localizability detection, and localization algorithm design. This article presents efficient algorithms to partition MRRCs and MGRCs and develops an open-sourced toolbox, GPART, for these algorithms to be conveniently used by the society. We firstly propose conditions and an efficient algorithm to merge the over-constrained regions to form the maximal redundant rigid components (MRRC). The detected MRRCs are proved to be maximal and all the MRRCs are guaranteed to be detected. The time to merge the over-constrained regions is linear to the number of nodes in the over-constrained components. To detect MGRCs, the critical problem is to decompose 3-connected components in each MRRC. We exploit SPQR-tree based method and design a local optimization algorithm, called MGRC_acce to prune the unnecessary decomposition operations so that the SPQR-tree functions can be called much less number of times. We prove the MGRCs can be detected inside MRRCs using at most O(mn ) time. Then a GPART toolbox is developed and extensively tested in graphs of different densities. We show the proposed MRRC and MGRC detection algorithms are valid and MGRC_acce greatly outperforms the direct SPQR-tree based decomposition algorithm. GPART is outsourced at https://github.com/inlab-group/gpart .

11‐5: Invited Paper: Evolving into an Era of Natively Flexible Smart Systems

Natively flexible electronics allow for ultra‐thin functionality to be added to wearable, conformal large‐area sensing applications, reducing or eliminating the need for bulky rigid components and dramatically improving both form factor and cost of the final system. Flexible Hybrid Electronics (FHE), which combine flexible and rigid components, are increasingly used for sensing applications like health patches, industrial sensing, robotics, augmented and virtual reality, etc. Thin‐Film Transistor (TFT) display manufacturing technologies are well established and have been leading the drive for cost and form‐factor optimization. In this article, we review an intersection of these technologies for sensing applications, predicting the emergence of smart systems made up of only low cost natively flexible electronic components including printed sensors, flexible ICs, printed batteries, printed antennas, and flexible displays.

Fractional Order Control of Continuum Soft Robots: Combining Decoupled/Reduced-Dynamics Models and Robust Fractional Order Controllers for Complex Soft Robot Motions

Continuum soft robots are made up of soft material components (referred to as continuum), rigid components, actuators, and sensors. By structurally deforming the continuum, a motion of the entire system is initiated. To capture the interaction of the actuators on the soft material deformation and the corresponding sensor readings, mathematical models involving geometrical, material, and inertia parameters of the physical system must be set up to predict its complex physical behavior.

Experimental study on dynamic compression behavior characteristics and stress wave propagation law of rigid-flexible combinations under cyclic bi-directional impact loading

To explore the dynamic compression behavior and damage evolution characteristics of “rigid-flexible coupling” surrounding rock supporting structure. Split Hopkinson pressure bar (SHPB) was used to carry out constant amplitude cyclic bi-directional impact compression tests on the combination specimens of “rigid-rigid: rock (sandstone)-like material (RLM) - normal cement mortar (NCM)", “rigid-flexible: RLM - rubber cement mortar (RCM)" and “flexible-rigid: RCM - high-performance supporting concrete (HPSC)". The characteristics of stress-strain curve evolution, stress attenuation, strain growth, energy transformation, damage evolution characteristics, and damage state were compared and analyzed. The results show that compared with RLM-NCM, RLM-RCM and RCM-HPSC had remarkable dynamic yield ductility and excellent impact resistance. RCM and HPSC can work together to hinder the dynamic damage development of “rigid-flexible coupling” supporting structure and surrounding rock. Based on the one-dimensional stress wave propagation theory, the stress wave propagation models of rigid-flexible combination specimens under SHPB cyclic bi-directional impact were established, and the corresponding stress wave propagation equations were derived, which profoundly revealed the propagation law and attenuation mechanism of stress waves in SHPB impact rigid-flexible combination tests. Finally, based on the energy drive theory and residual energy theory, the impact instability energy criteria of surrounding rock under the rigid component combined support system and “rigid-flexible coupling” component combined support system were analyzed and discussed.

Phylogenetic and comparative genomics establishes origin of paralogy between homologs of AtMYB42 and AtMYB85 in last common ancestor of Brassicaceae via segmental duplication

Origin and evolution of secondary cell wall is considered key to colonization of terrestrial habitat by plants. The primary component of secondary cell wall, lignin, imparts strength and rigidity and enables plants to endure negative pressure created during transpiration. Members of the MYB transcription family, AtMYB42 and AtMYB85, play critical roles as regulators of lignin biosynthesis. Inspite of their functional significance, evolutionary history of homologs of AtMYB42 and AtMYB85 across land plants remains to be investigated. Our analysis revealed that homologs of AtMYB42 and AtMYB85 as two distinct genes are not present in any plant lineage outside Brassicaceae and only the ancestral form exists as AtMYB42/AtMYB85. Analysis of homologs of AtMYB42 and AtMYB85 across green plants combined with comparative genomics, selection pressure, and character-state reconstruction reveals that AtMYB42 and AtMYB85 are paralogous, and arose via segmental duplication, which may coincide with the α-event of WGD that occurred after the split of Brassicaceae-Caricaceae from the last common ancestor. Within Brassicaceae, homeologs and paralogs that arose as a result of polyploidization, and species- and lineage-specific changes could be observed. For instance, homologs of AtMYB42 were found to be deleted from the entire Brassica lineage. Analysis of homeologous segments in neopolyploids (B. napus, B. juncea, Camelina sativa), and meso-polyploid (B. rapa) revealed differential degrees of gene loss and retention. In Brassicaceae, homologs of AtMYB42 were found to be under purifying selection and of AtMYB85 under positive selection. High sequence identity in the coding region between homologs of AtMYB42 and AtMYB85 is indicative of redundant roles, and the loss of homologs of AtMYB42 in Brassica may be compensated by presence of AtMYB85 homologs and homeologs. The study thus forms the basis to investigate questions on regulatory diversification owing to variation in cis-elements between the paralogs and among homeologs, and, impact of differential selection pressure vis-a-vis redundant function.

Molecular Mobility in Keratin-Rich Materials Monitored by Nuclear Magnetic Resonance: A Tool for the Evaluation of Structure-Giving Properties.

Keratins are structural proteins that are abundant in human skin, nails, and hair, where they provide mechanical strength. In the present study, we investigate the molecular mobilities and structures of three keratin-rich materials with clearly different mechanical properties: nails, stratum corneum (upper layer of epidermis), and keratinocytes (from lower layer of epidermis). We use solid-state NMR on natural-abundance 13C to characterize small changes in molecular dynamics in these biological materials with close to atomistic resolution. One strong advantage of this method is that it detects small fractions of mobile components in a molecularly complex material while it simultaneously gives information on the rigid components in the very same sample. The molecular mobility can be linked to mechanical material properties in different conditions, including hydration or exposure to osmolytes or organic solvents. Importantly, the study revealed that the response to both hydration and addition of urea is clearly different for the nail keratin compared to the stratum corneum keratin. The comparative examination of these materials may provide a better understanding of skin diseases originating from keratin malfunction and contributes to the design and development of new materials.

Force constraint-based approach to compute the position and orientation of parts assembled by multiple non-ideal planes

The occurrence of position and orientation deviations (PODs) during the assembly of rigid components, which is caused by non-ideal morphologies on the manufactured surface, directly affects the performance of the mechanical product. Moreover, the generated PODs are influenced by the deformation of the contact points because of the assembly force. Therefore, to control the product performance in the design stage, the PODs should be computed considering both the non-ideal morphologies of the mating surfaces as well as the forces acting on the assembly. However, most existing approaches to POD computation ignore the effects of the assembly force. Moreover, they often focus on assemblies with a single mating plane. To address this problem, a force constraint-based approach is proposed in this study, which considers both the non-ideal morphologies of multiple mating planes and the assembly forces. The principle of force balance is employed to determine whether the assembly is completed. Different tentative positions and orientations are determined according to the strategies of progressively approaching position and orientation, and recursion of degrees of freedom (DOFs). An unbalance indicator was established in this study to determine whether the force balance in the direction of each DOF is satisfied. As long as the force balance of all DOFs to be constrained is achieved, the assembly of parts is considered to be finalised, and the final PODs are acquired. Finally, the PODs of a typical assembly with multi-mating planes and the guiding accuracy of a sliding workbench are computed according to the non-ideal morphologies modelled from the perspective of manufacturing errors, thereby validating the proposed approach.