arXiv subjects

Ruike Renee Zhao

Publications and source records attributed to Ruike Renee Zhao.

At least 19 recordsLinked to original sources

arXiv2026

Optimization of Magnetic Milli-Spinner for Robotic Endovascular Intervention

Vascular diseases such as atherosclerosis, thrombosis, and aneurysms can lead to life-threatening medical events. Conventional catheter- or guidewire-based interventional devices often struggle to navigate through highly tortuous vasculature. The recently developed multifunctional magnetic milli-spinner offers a promising wireless solution by integrating a central through-hole and side slits into a cylindrical body with helical fins, enabling rapid and stable navigation for clot debulking, targeted drug delivery, and aneurysm treatment. Here, we combine computational fluid dynamics simulations with experimental validation to optimize the milli-spinner's structural design for high-velocity propulsion and high-efficiency clot debulking in tubular flow environments. By systematically investigating the effects of through-hole radius, fin number, fin helical angle, and slit dimension on propulsion performance, the optimized milli-spinner achieves swimming velocities of 55 cm/s (175 body lengths per second) in saline water and 44 cm/s (140 body lengths per second) in a fluid with viscosity (3.5 mPa.s) comparable to that of arterial blood at high shear rates, far exceeding existing untethered magnetic robots in tubular environments (less than 80 body lengths per second). This exceptional velocity enables stable upstream operation against strong physiological flows representative of major arteries and veins, establishing the milli-spinner as a robust untethered navigation platform for operation in high-flow, tortuous vasculature.

physics.med-ph↗

arXiv2026

Spatiotemporal modulation of surface texture for information encoding and object manipulation

Dynamically tunable surface textures offer a powerful route to spatiotemporally regulate surface and interfacial properties, enabling emerging applications ranging from adaptive optics to soft robotic manipulation. However, achieving programmable, reversible, and spatiotemporal modulation of surface texture remains a fundamental challenge. Here, we present a photothermal-actuated liquid crystal elastomer bilayer that enables reversible, on-demand spatiotemporal modulation of surface textures through dynamically emerging and propagating wrinkles. Using direct laser writing or projected light fields, programmable and self-erasable wrinkle patterns are generated for dynamic information encoding. This spatiotemporal wrinkling enables object manipulation across diverse geometries, including uphill transport and navigation along predesigned paths. By coupling wrinkle-driven motion with thermally reversible dynamic bonding, the bilayer further enables assembly and disassembly of dynamic polymers, as well as cargo transportation. This work demonstrates spatiotemporally programmable wrinkling as a powerful mechanism for dynamic modulation of surface textures, establishing a versatile platform for multifunctional and reconfigurable smart surfaces.

physics.app-ph↗

arXiv2025

2D-to-3D transformation of ring origami via snap-folding instabilities

Ring origami, consisting of closed-loop rods, is a class of shape-morphing structures that undergo shape transformation through folding enabled by snap-buckling instabilities, referred to as snap-folding instabilities. Previous studies have shown that 2D ring origami composed of rod segments with in-plane natural curvature (i.e., the stress-free curved state lies in the plane of the planar ring) can achieve diverse and intriguing 2D-to-2D shape transformations. Here, we propose a 2D-to-3D shape transformation strategy for ring origami by introducing out-of-plane natural curvature (i.e., the stress-free curved state lies in a plane perpendicular to the planar ring) into the rod segments. Due to natural curvature-induced out-of-plane bending moments, a 2D elastic ring spontaneously snaps out-of-plane and reaches equilibrium in a 3D configuration. These snapping-induced out-of-plane shape transitions not only enable self-guided, spontaneous shape morphing, but also allow the construction of complex structures from simple geometries, making them promising for the design of functional deployable and foldable structures. By combining a multi-segment Kirchhoff rod model with finite element simulations and experiments, we systematically investigate the 3D equilibrium states and transition behavior of these systems. Using square and hexagonal rings as representative examples, we demonstrate that by rationally designing the out-of-plane natural curvature of rod segments, 2D rings can exhibit a range of functional behaviors, including spontaneous 2D-to-3D shape transformation (e.g., planar square to sphere) via snap-folding, multistability with various 3D configurations, and monostability with a compact zero-energy 3D configuration.

physics.app-ph↗

arXiv2025

Elastic Rod Origami (RodOri) for Programming Static and Dynamic Mechanical Properties

Reconfigurable mechanical systems enable precise programmable control over structural properties, opening new opportunities in architected materials, adaptive devices, and multifunctional structures. Here, we introduce elastic rod origami (RodOri), a platform that exploits remarkably simple elements (pre-stressed, naturally curved rods) into a system with an extraordinary degree of multistability and configurational richness. For example, a single 6-rod RodOri unit can easily access 11 distinct configurations, far exceeding the reconfigurability of conventional origami or general mechanical reconfigurable systems. Individual rods, constrained under clamped boundary conditions, undergo snapping transitions between discrete morphologies whose strain energy and stiffness are precisely prescribed by their natural curvature. Assembling these rods into modular multi-rod architectures yields metamaterials with numerous stable configurations that can be selectively and reversibly programmed. This configurational diversity enables tunable static stiffness, nonlinear force response, and thus enables tunable dynamic behaviors such as vibration filtering, wave-propagation switching, and mode conversion within a single, easily-manufactured platform. By leveraging curvature-induced mechanical instability, RodOri unlocks highly programmable static and dynamic mechanical behavior, offering new design strategies in reconfigurable structures, soft robotics, medical devices, and adaptive materials.

physics.app-ph↗

arXiv2025

Bioinspired Synergistic Texture and Color Modulation Enabled by Surface Instability of Cholesteric Liquid Crystal Elastomers

Certain cephalopods can dynamically camouflage by altering both skin texture and color to match their surroundings. Inspired by this capability, we present a cholesteric liquid crystal elastomer-liquid crystal elastomer (CLCE-LCE) bilayer capable of simultaneous, reversible modulation of surface texture and structural color through programmable wrinkling. By tuning the bilayer's fabrication parameters, on-demand wrinkle morphologies and color combinations are achieved. Spatially selective UV curing allows localized surface textures, while chemical patterning of the CLCE layer enables region-specific color responses, expanding the design space for multifunctional, spatially encoded optical materials. The CLCE-LCE bilayer enables dynamic thermal regulation by tuning light absorption through synergistically modulating surface morphology and color. Notably, this system achieves strain-dependent multiscale encoding via multistep selective UV curing, revealing distinct visual content under different applied strains. This work establishes a versatile platform that merges surface instabilities with tunable structural coloration, advancing intelligent materials with programmable, strain-responsive surface and optical properties.

physics.app-ph↗

arXiv2025

Clot Treatment via Compression- and Shear-Induced Densification of Fibrin Network Microstructure: A Combined in Vitro and In Silico Investigation

Blood clots, consisting of red blood cells (RBCs) entrapped within a fibrin network, can cause life-threatening conditions such as stroke and heart attack. The recently developed milli-spinner thrombectomy device presents a promising mechanical approach to removing clots by substantially modifying the microstructure of the blood clot, resulting in up to 95% volume reduction through combined compressive and shear forces. To better understand the mechanism and optimize this approach, it is important to quantitatively understand of how compression and shear loadings alter the clot structure. In this study, we combine in vitro experiments with dissipative particle dynamics (DPD) simulations to investigate the effectiveness of clot debulking under integrated compression and shear. Controlled experiments quantify clot volume changes, while simulations offer microscopic insight into fibrin network densification and RBC release. This integrated approach enables a systematic evaluation of mechanical response and microstructure change of different clot types, providing fundamental knowledge to guide the rational design of next-generation mechanical thrombectomy technologies.

physics.bio-ph↗

arXiv2025

Ultra-Efficient Kidney Stone Fragment Removal via Spinner-Induced Synergistic Circulation and Spiral Flow

Kidney stones can cause severe pain and complications such as chronic kidney disease or kidney failure. Retrograde intrarenal surgery (RIRS), which uses laser lithotripsy to fragment stones for removal via a ureteroscope, is widely adopted due to its safety and effectiveness. However, conventional fragment removal methods using basketing and vacuum-assisted aspiration are inefficient, as they can capture only 1 to 3 fragments (1--3\,mm in size) per pass, often requiring dozens to hundreds of ureteroscope passes during a single procedure to completely remove the fragments. These limitations lead to prolonged procedures and residual fragments that contribute to high recurrence rates. To address these limitations, we present a novel spinner device that enables ultra-efficient fragment removal through spinning-induced localized suction. The spinner generates a three-dimensional spiral and circulating flow field that dislodges and draws fragments into its cavity even from distances over 20\,mm, eliminating the need to chase fragments. It can capture over 60 fragments (0.5--2\,mm) or over 15 larger fragments (2--3\,mm) in a single pass, significantly improving removal efficiency. In this work, the spinner design is optimized via computational fluid dynamics to maximize suction performance. \textit{In vitro} testing demonstrates near 100\% capture rates for up to 60 fragments in a single operation and superior large-distance capture efficacy compared to vacuum-assisted methods. \textit{Ex vivo} testing of the integrated spinner-ureteroscope system in a porcine kidney confirmed its high performance by capturing 45 fragments in just 4 seconds during a single pass and achieving complete fragment clearance within a few passes.

physics.app-ph↗

arXiv2025

Buckling and post-buckling of cylindrical shells under combined torsional and axial loads

The buckling behavior of cylindrical shells has gained significant interest over the past century due to its rich nonlinear behavior and broad engineering applications. While the buckling of cylindrical shells under a single load (e.g., compression or torsion) has been extensively studied, the buckling behavior under combined torsional and axial loads remains largely unexplored. In this paper, based on a combination of experiments, theoretical modeling, and finite element simulations, we systematically investigate the buckling and post-buckling behavior of cylindrical shells under combined torsional and axial loads. Three different types of combined loads are considered: compression with pre-torsion, torsion with pre-tension, and torsion with pre-compression. The theoretical model is established within the framework of the Donnell shell theory and solved using the Galerkin method, through which the critical buckling load, critical circumferential wavenumber, buckling pattern, and post-buckling equilibrium path of clamped-clamped thin cylindrical shells under various types of loads can be determined. The theoretical predictions agree well with finite element simulations and qualitatively capture the various buckling phenomena observed in the experiments. It is found that cylindrical shells exhibit quite different post-buckling behavior under combined loads compared to under a single compressive or torsional load. For instance, when a clamped-clamped thin cylindrical shell is subjected to pure torsion or torsion with a relatively small pre-compression, it consistently shows a diagonal-shaped pattern during deformation. However, with a relatively large pre-compression, the shell transitions from a diagonal-shaped pattern to a twisted diamond-shaped pattern.

nlin.PS↗

arXiv2025

Multiple equilibrium states of a curved-sided hexagram: Part I-Stability of states

The stability of the multiple equilibrium states of a hexagram ring with six curved sides is investigated. Each of the six segments is a rod having the same length and uniform natural curvature. These rods are bent uniformly in the plane of the hexagram into equal arcs of 120deg or 240deg and joined at a cusp where their ends meet to form a 1-loop planar ring. The 1-loop rings formed from 120deg or 240deg arcs are inversions of one another and they, in turn, can be folded into a 3-loop straight line configuration or a 3-loop ring with each loop in an "8" shape. Each of these four equilibrium states has a uniform bending moment. Two additional intriguing planar shapes, 6-circle hexagrams, with equilibrium states that are also uniform bending, are identified and analyzed for stability. Stability is lost when the natural curvature falls outside the upper and lower limits in the form of a bifurcation mode involving coupled out-of-plane deflection and torsion of the rod segments. Conditions for stability, or lack thereof, depend on the geometry of the rod cross-section as well as its natural curvature. Rods with circular and rectangular cross-sections will be analyzed using a specialized form of Kirchhoff rod theory, and properties will be detailed such that all four of the states of interest are mutually stable. Experimental demonstrations of the various states and their stability are presented. Part II presents numerical simulations of transitions between states using both rod theory and a three-dimensional finite element formulation, includes confirmation of the stability limits established in Part I, and presents additional experimental demonstrations and verifications.

physics.app-ph↗

arXiv2025

Multiple equilibrium states of a curved-sided hexagram: Part II-Transitions between states

Curved-sided hexagrams with multiple equilibrium states have great potential in engineering applications such as foldable architectures, deployable aerospace structures, and shape-morphing soft robots. In Part I, the classical stability criterion based on energy variation was used to study the elastic stability of the curved-sided hexagram and identify the natural curvature range for stability of each state for circular and rectangular rod cross-sections. Here, we combine a multi-segment Kirchhoff rod model, finite element simulations, and experiments to investigate the transitions between four basic equilibrium states of the curved-sided hexagram. The four equilibrium states, namely the star hexagram, the daisy hexagram, the 3-loop line, and the 3-loop "8", carry uniform bending moments in their initial states, and the magnitudes of these moments depend on the natural curvatures and their initial curvatures. Transitions between these equilibrium states are triggered by applying bending loads at their corners or edges. It is found that transitions between the stable equilibrium states of the curved-sided hexagram are influenced by both the natural curvature and the loading position. Within a specific natural curvature range, the star hexagram, the daisy hexagram, and the 3-loop "8" can transform among one another by bending at different positions. Based on these findings, we identify the natural curvature range and loading conditions to achieve transition among these three equilibrium states plus a folded 3-loop line state for one specific ring having a rectangular cross-section. The results obtained in this part also validate the elastic stability range of the four equilibrium states of the curved-sided hexagram in Part I. We envision that the present work could provide a new perspective for the design of multi-functional deployable and foldable structures.

physics.app-ph↗

arXiv2025

Selective Actuation Enabled Multifunctional Magneto-mechanical Metamaterial for Programming Elastic Wave Propagation

Active metamaterials are a type of metamaterial with tunable properties enabled by structural reconfigurations. Existing active metamaterials often achieve only a limited number of structural reconfigurations upon the application of an external load across the entire structure. Here, we propose a selective actuation strategy for inhomogeneous deformations of magneto-mechanical metamaterials, which allows for the integration of multiple elastic wave tuning functionalities into a single metamaterial design. Central to this actuation strategy is that a magnetic field is applied to specific unit cells instead of the entire metamaterial, and the unit cell can transform between two geometrically distinct shapes, which exhibit very different mechanical responses to elastic wave excitations. Our numerical simulations and experiments demonstrate that the tunable response of the unit cell, coupled with inhomogeneous deformation achieved through selective actuation, unlocks multifunctional capabilities of magneto-mechanical metamaterials such as tunable elastic wave transmittance, elastic waveguide, and vibration isolation. The proposed selective actuation strategy offers a simple but effective way to control the tunable properties and thus enhances the programmability of magneto-mechanical metamaterials, which also expands the application space of magneto-mechanical metamaterials in elastic wave manipulation.

physics.app-ph↗

arXiv2024

Magnetic Milli-spinner for Robotic Endovascular Surgery

Vascular diseases such as thrombosis, atherosclerosis, and aneurysm, which can lead to blockage of blood flow or blood vessel rupture, are common and life-threatening. Conventional minimally invasive treatments utilize catheters, or long tubes, to guide small devices or therapeutic agents to targeted regions for intervention. Unfortunately, catheters suffer from difficult and unreliable navigation in narrow, winding vessels such as those found in the brain. Magnetically actuated untethered robots, which have been extensively explored as an alternative, are promising for navigation in complex vasculatures and vascular disease treatments. Most current robots, however, cannot swim against high flows or are inadequate in treating certain conditions. Here, we introduce a multifunctional and magnetically actuated milli-spinner robot for rapid navigation and performance of various treatments in complicated vasculatures. The milli-spinner, with a unique hollow structure including helical fins and slits for propulsion, generates a distinct flow field upon spinning. The milli-spinner is the fastest-ever untethered magnetic robot for movement in tubular environments, easily achieving speeds of 23 cm/s, demonstrating promise as an untethered medical device for effective navigation in blood vessels and robotic treatment of numerous vascular diseases.

cs.RO↗

arXiv2024

Milli-spinner thrombectomy

Blockage of blood flow in arteries or veins by blood clots can lead to serious medical conditions. Mechanical thrombectomy (MT), minimally invasive endovascular procedures that utilize aspiration, stent retriever, or cutting mechanisms for clot removal have emerged as an effective treatment modality for ischemic stroke, myocardial infarction, pulmonary embolism, and peripheral vascular disease. However, state-of-the-art MT technologies still fail to remove clots in approximately 10% to 30% of patients, especially when treating large-size clots with high fibrin content. In addition, the working mechanism of most current MT techniques results in rupturing or cutting of clots which could lead to clot fragmentation and distal emboli. Here, we report a new MT technology based on an unprecedented mechanism, in which a milli-spinner mechanically debulks the clot by densifying its fibrin fiber network and discharging red blood cells to significantly reduce the clot volume for complete clot removal. This mechanism is achieved by the spin-induced compression and shearing of the clot. We demonstrate its effective clot-debulking performance with clot volumetric reduction of up to 90% on various sizes of clots with diverse clot compositions. Milli-spinner MT in both in-vitro pulmonary and cerebral artery flow models and in-vivo swine models demonstrate high-fidelity revascularization. The milli-spinner MT is the first reported mechanism that directly modifies the clot microstructure to facilitate clot removal, which also results in markedly improved MT efficacy compared to the existing MT mechanisms that are based on clot rupturing and cutting. This technology introduces a unique mechanical way of debulking and removing clots for future MT device development, especially for the treatment of ischemic stroke, pulmonary emboli, and peripheral thrombosis.

physics.app-ph↗

arXiv2023

Physics-aware differentiable design of magnetically actuated kirigami for shape morphing

Shape morphing that transforms morphologies in response to stimuli is crucial for future multifunctional systems. While kirigami holds great promise in enhancing shape-morphing, existing designs primarily focus on kinematics and overlook the underlying physics. This study introduces a differentiable inverse design framework that considers the physical interplay between geometry, materials, and stimuli of active kirigami, made by soft material embedded with magnetic particles, to realize target shape-morphing upon magnetic excitation. We achieve this by combining differentiable kinematics and energy models into a constrained optimization, simultaneously designing the cuts and magnetization orientations to ensure kinematic and physical feasibility. Complex kirigami designs are obtained automatically with unparallel efficiency, which can be remotely controlled to morph into intricate target shapes and even multiple states. The proposed framework can be extended to accommodate various active systems, bridging geometry and physics to push the frontiers in shape-morphing applications, like flexible electronics and minimally invasive surgery.

physics.app-ph↗

arXiv2023

Stiffness Change for Reconfiguration of Inflated Beam Robots

Active control of the shape of soft robots is challenging. Despite having an infinite number of passive degrees of freedom (DOFs), soft robots typically only have a few actively controllable DOFs, limited by the number of degrees of actuation (DOAs). The complexity of actuators restricts the number of DOAs that can be incorporated into soft robots. Active shape control is further complicated by the buckling of soft robots under compressive forces; this is particularly challenging for compliant continuum robots due to their long aspect ratios. In this work, we show how variable stiffness can enable shape control of soft robots by addressing these challenges. Dynamically changing the stiffness of sections along a compliant continuum robot can selectively "activate" discrete joints. By changing which joints are activated, the output of a single actuator can be reconfigured to actively control many different joints, thus decoupling the number of controllable DOFs from the number of DOAs. We demonstrate embedded positive pressure layer jamming as a simple method for stiffness change in inflated beam robots, its compatibility with growing robots, and its use as an "activating" technology. We experimentally characterize the stiffness change in a growing inflated beam robot and present finite element models which serve as guides for robot design and fabrication. We fabricate a multi-segment everting inflated beam robot and demonstrate how stiffness change is compatible with growth through tip eversion, enables an increase in workspace, and achieves new actuation patterns not possible without stiffening.

cs.RO↗

arXiv2023

Magneto-Mechanical Bilayer Metasurface with Global Area-Preserving Density Tunability for Acoustic Wave Regulation

Metasurfaces have extensive potential in acoustic cloaking, optical scattering, and electromagnetic antenna due to their unprecedented properties and the ability to conform to curved substrates. Active metasurfaces have attracted significant research attention because of their on-demand tunable properties and performances through shape reconfigurations. They normally achieve active properties through internal structural deformations, which often lead to changes in overall dimensions. This also demands the corresponding alterations of the conforming substrate, which could be a significant limitation for their practical applications. To date, achieving area-preserving active metasurfaces with distinct shape reconfigurations remains a prominent challenge. In this paper, we present magneto-mechanical bilayer metasurfaces that demonstrate area density tunability with area-preserving capability. The bilayer metasurfaces primarily consist of two arrays of magnetic soft materials with distinct magnetization distributions. Under an external magnetic field, each layer behaves differently, which allows the metasurface to reconfigure its shape into multiple modes and thus significantly tune its area density without changing its overall dimensions. The area-preserving multimodal shape reconfigurations are further exploited as active acoustic wave regulators to tune bandgaps and wave propagations. The bilayer approach thus provides a new concept to design area-preserving active metasurfaces for broader practical applications.

physics.app-ph↗

arXiv2023

On the Elastic Stability of Folded Rings in Circular and Straight States

Single-loop elastic rings can be folded into multi-loop equilibrium configurations. In this paper, the stability of several such multi-loop states which are either circular or straight are investigated analytically and illustrated by experimental demonstrations. The analysis ascertains stability by exploring variations of the elastic energy of the rings for admissible deformations in the vicinity of the equilibrium state. The approach employed is the conventional stability analysis for elastic conservative systems which differs from most of the analyses that have been published on this class of problems, as will be illustrated by reproducing and elaborating on several problems in the literature. In addition to providing solutions to two basic problems, the paper analyses and demonstrates the stability of six-sided rings that fold into straight configurations.

physics.app-ph↗

arXiv2023

Liquid Crystal Elastomer-Liquid Metal Composite: Ultrafast, Untethered, and Programmable Actuation by Induction Heating

Liquid crystal elastomers (LCEs) are a stimuli-responsive material which has been intensively studied for applications including artificial muscles, shape morphing structures, and soft robotics, due to its capability of large, programmable, and fully reversible strains. To fully take advantage of LCEs, rapid, untethered, and programmable actuation methods are highly desirable. Here, we report a liquid crystal elastomer-liquid metal (LCE-LM) composite, which enables ultrafast actuations and high heating programmability by eddy current induction heating. The composite consists of LM sandwiched between two 3D-printed LCE layers via direct ink writing (DIW). When subject to a high-frequency alternating magnetic field, the composite can be actuated in milli-seconds. By moving the magnetic field, the eddy current can be spatially controlled for selective actuation. Additionally, sequential heating is achievable by programming the LM thickness distribution in a specimen. With these capabilities, the LCE-LM composite is further exploited for multimodal deformation of a pop-up structure, on ground omnidirectional robotic motion, in water targeted object manipulation, and crawling.

physics.app-ph↗