Publications

Endovascular interventions are essential for treating cerebrovascular diseases, yet their monitoring methods commonly rely on ionizing radiation and contrast agents, posing unnecessary risks to patients and clinicians. We present a multifunctional optoacoustically augmented magnetic guidewire (OptoMaG) that integrates optoacoustic imaging with magnetic navigation to enable radiation-free, image-guided interventions. The ~250-micrometer flexible guidewire incorporates a 460-nanometer luminescent core with an enhanced optoacoustic signature and a FePt magnetic tip for precise, steerable control. Proof-of-concept studies show that OptoMaG can be actively navigated with external magnetic fields to traverse a 3D human-scale cerebrovascular phantom and accurately reach target brain sites. Beyond navigation, the FePt tip enables localized thermal ablation under remote radiofrequency stimulation, highlighting its theranostic potential for tumor treatment. In addition, OptoMaG functions as a light source for photodynamic therapy, selectively activating photosensitizers to destroy tumor cells while preserving healthy tissue. Collectively, OptoMaG provides a safe, radiation-free platform merging real-time navigation with targeted therapeutic capabilities.

Controlling fluidic flows in active droplets is crucial in developing intelligent models to understand and mimic single-celled microorganisms. Typically, these fluidic flows are affected by the interfacial dynamics of chemical agents. We found that these flows can be reconfigured by the mere presence of an anisotropic solid boundary embedded within active droplets. Spontaneous fluidic flows dynamically orient an embedded magnetic cluster, and the magnetic cluster, when realigned, causes these flows to reorient, thus providing control over the propulsion dynamics of chemotactic emulsions. When continuously perturbed, achiral emulsions exhibit emergent chiral motion with rotating fluidic flows. Such solid-fluid interactions occur in a number of self-propelling oil droplet systems, thereby enabling control over the emergent collective behaviors of chemically distinct active droplets.

Wireless trackers have emerged as a crucial technology in minimally invasive medical procedures with their remote localization capabilities. Existing trackers suffer from miniaturization issues and complex designs, which limit their integration into medical devices. We present nuclear magnetic resonance (NMR) magnetic sensing, a quantum sensing approach with nT sensitivity for wireless magnetic tracking. NMR magnetic sensing enables millimeter-scale tracking accuracy and versatile miniaturized tracker designs for minimally invasive medical devices in magnetic resonance imaging scanners. As examples, we demonstrate miniature magnetic trackers with submillimeter-scale diameters for guidewires and optic fibers, flexible magnetic trackers for soft devices, and ferrofluidic trackers for shape-morphing devices. With the demonstrated miniaturization and wide range of tracker design possibilities, wireless magnetic tracking with NMR is promising for future minimally invasive medical operations.

Precision drug delivery remains a significant challenge due to limitations in drug loading, targeted release, precise navigation, and real-time monitoring. Here, the study reports a magnetic microrobot platform (MMP) that integrates high-capacity drug loading, magnetically actuated collective navigation, controlled drug release, and real-time 3D optoacoustic imaging in a single system. The MMP exploits synergistic advantages by embedding hard-magnetic FePt nanoparticles in a degradable ZIF-8 shell, achieving a drug loading efficiency of ≈93.9% and enabling precise release in response to pH changes and radiofrequency-induced heating. Reconfigurable swarm behavior strategies significantly enhance the navigation efficiency of microrobots against physiological blood flows within complex cerebral vasculature. The ex vivo and in vivo experiments further demonstrate strong contrast characteristics of the microrobots, enabling high-resolution visualization of deep vascular structures and dynamic tracking of MMP with real-time 3D optoacoustic imaging. This multifunctional strategy paves the way for clinical translation and precision therapy in complex biological settings.

Giant unilamellar vesicles (GUVs), soft cell-sized compartments formed through the self-assembly of lipid molecules, have long been utilized as model systems and passive carriers in membrane biophysics and biomedical applications. However, their potential as dynamically responsive and motile systems remains largely untapped due to challenges in achieving controlled and sustained motion in soft, deformable structures. Here, an autonomous cell-like microrobot through the emergent self-assembly of GUVs (5-10 µm) and silica microparticles (1-3 µm) under alternating current electric fields is realized. Self-propulsion arises from asymmetric self-organization of the particles on the vesicle surface, enabling a reversible transformation of the assembly into an active structure. Unlike rigid colloidal systems, GUVs introduce unique features enabled by their soft lipid membranes: shape deformations, membrane tension-dependent motility, and field-triggered live bacteria release via vesicle bursting. Through experiments and simulations, the mechanisms underlying self-assembly and propulsion are investigated, and a dynamic phase diagram is constructed to map the motion regime as a function of field parameters. Finally, it is shown that these self-assembled structures are capable of reconfiguration in response to local constraints in the environment, suggesting potential applications in complex environments and advancing the potential of GUVs toward the rational design of cell-like microrobots or artificial cell systems.

Wireless neural interfaces are emerging as a minimally invasive treatment option for neurological disorders. Among the wireless technologies, magnetically powered systems are effective for targeting deep brain sites. However, dependence on high-frequency electromagnetic fields in such systems limits their safe implementation. In this study, we demonstrate the use of millimeter-scale magnetoelectric (ME) films as a direct neural interface for wireless neurostimulation, powered by static and alternating magnetic fields in the nonresonant regime (10 hertz). To accomplish this objective, electrical potential trends of the ME films under varying low-frequency magnetic fields are investigated and used to demonstrate neural stimulation by calcium imaging on primary neurons in vitro via a capacitive-like charge injection mechanism. In addition, electrical polarization orientation is revealed as a critical design parameter in direct neuron-ME interfaces. These findings collectively demonstrate the potential of nonresonant powering of ME films as a promising minimally invasive wireless neural stimulation technique.

Covalent organic frameworks (COFs) have been emerging as versatile reticular materials due to their tunable structures and functionalities, enabled by precise molecular engineering at the atomic level. While the integration of multiple components into COFs has substantially expanded their structural complexity, the strategic engineering of diverse functionalities within a single framework via the random distribution of linkers with varying lengths remains largely unexplored. Here, we report a series of highly crystalline mixed-length multivariate COFs synthesized using azobenzene and bipyridine as linkers, where tuning the ratio of linkers and incorporating palladium effectively modulates the balance between near-infrared (NIR) light absorption and catalytic sites for NIR-generation of hydrogen peroxide (H2O2). Capitalizing on the deep tissue penetration of NIR light and the generated H2O2 as reactive oxygen species, as a proof of concept, the optimal mixed-length multivariate COF reduces breast cancer cell viability by almost 90% after 1 h of irradiation in a combined in vitro photodynamic therapy and drug delivery.

Magnetic soft robots offer considerable potential across various scenarios, such as biomedical applications and industrial tasks, because of their shape programmability and reconfigurability, safe interaction and biocompatibility1,2,3,4. Despite recent advances, magnetic soft robots are still limited by the difficulties in reprogramming their required magnetization profiles in real time on the spot (in situ), which is essential for performing multiple functions or executing diverse tasks5,6. Here we introduce a method for real-time in situ magnetization reprogramming that enables the rearrangement and recombination of magnetic units to achieve diverse magnetization profiles. We explore the applications of this method in structures of varying dimensions, from one-dimensional tubes to three-dimensional frameworks, showcasing a diverse and expanded range of configurations and their deformations. This method also demonstrates versatility in diverse scenarios, including navigating around objects without undesired contact, reprogramming cilia arrays, managing multiple instruments cooperatively or independently under the same magnetic field, and manipulating objects of various shapes. These abilities extend the range of applications for magnetic actuation technologies. Furthermore, this method frees magnetic soft robots from the sole reliance on external magnetic fields for shape change, facilitating unprecedented modes and varieties of deformation while simultaneously reducing the need for complex magnetic field generation systems, thereby opening avenues for the development of magnetic actuation technologies.

Bacterial biohybrid microrobots possess significant potential for targeted cargo delivery and minimally invasive therapy. However, many challenges, such as biocompatibility, stability, and effective cargo loading, remain. Bacterial membrane vesicles, also referred to as minicells, offer a promising alternative for creating sub-micron scale biohybrid swimmers (minicell biohybrids) due to their active metabolism, non-dividing nature, robust structure, and high cargo-carrying capacity. Here, a biohybrid system is reported that utilizes motile minicells, ≈400 nm in diameter, generated by aberrant cell division of engineered Escherichia coli (E. coli), for the first time. Achieving over 99% purification from their parental bacterial cells, minicells are functionalized with magnetic nanoparticles (MNPs) to enable external magnetic control. Minicell biohybrids are capable of swimming at an average speed of up to 13.3 µm s−1 and being steered under a uniform magnetic field of 26 mT. Furthermore, they exhibit a significantly high drug loading capacity (2.8 µg mL−1) while maintaining their motility and show pH-sensitive release of anticancer drug doxorubicin hydrochloride (DOX) under acidic conditions. Additionally, drug-loaded minicell biohybrids notably reduce the viability of SK-BR-3 breast cancer cells in vitro. This study introduces minicell biohybrids and establishes their potential as magnetically guided, drug-loaded biohybrid systems for targeted therapies in future medical applications.

Intraocular drug implants are increasingly used for retinal treatments, such as age-related macular degeneration and diabetic macular edema, due to the rapidly aging global population. Although these therapies show promise in arresting disease progression and improving vision, intraocular implant-based therapies can cause unexpected complications that require further surgery due to implant dislocation or uncontrolled drug release. These frequent complications of intraocular drug implants can be overcome using magnetically controllable degradable milliscale swimmers (MDMS) with a double-helix body morphology. A biodegradable hydrogel, polyethylene glycol diacrylate, is employed as the primary 3D printing material of MDMS, and it is magnetized by decorating it with biocompatible polydopamine-encapsulated iron-platinum nanoparticles. MDMS have comparable dimensions to commercial intraocular implants that achieve translational motions in both aqueous and vitreous bodies. They can be imaged in real-time using optical coherence tomography, ultrasound, and photoacoustic imaging. Thanks to their biodegradable hydrogel-based structure, they can be loaded with anti-inflammatory drug molecules and release the medications without disrupting retinal epithelial viability and barrier function, and decrease proinflammatory cytokine release significantly. These magnetically controllable swimmers, which degrade in a couple of months, can be used for less invasive and more precise intraocular drug delivery compared to commercial intraocular drug implants.

Synthetic microrobots have gained significant attention due to their potential in various applications in biomedicine and lab-on-a-chip technologies. As a fundamental requirement, microrobots must navigate in 3D, effectively counteracting gravity to execute their tasks. However, locomotion at small scales presents numerous counterintuitive behaviors, primarily governed by the interactions between the microrobot's body and its surrounding boundaries. In this study, the locomotion of surface-rolling microrobots is investigated in 3D, particularly focusing on their ability to climb walls. Through a combination of experiments and computational fluid dynamics analyzes, it is demonstrated that the influence of gravity plays a secondary role in enabling surface-rolling microrobots to climb walls. Instead, locomotion capability in 3D settings is primarily determined by interactions with surrounding boundaries. The fundamental principles of surface-rolling locomotion in 3D spaces is elucidated and a design strategy aimed at optimizing fluid flow for efficient propulsion in future applications is proposed.

Magnetic surface microrollers have demonstrated promise as active drug delivery agents for targeted and minimally invasive disease treatment. Specifically, it can be employed in the circulatory system to locally release therapeutic agents at disease sites, minimizing systemic exposure and reducing side effects, particularly in the treatment of diseases like cancer. Previous research indicates that the design and shape of microrollers play a crucial role in safe navigation within blood vessels, with anisotropic microrollers exhibiting superiority due to favorable hydrodynamic interactions with nearby boundaries. In this study, the navigation potential of anisotropic microrollers is investigated in veins, venules, and capillaries through computational fluid dynamics analyses. These results indicate that robust locomotion is only achievable in larger vessels, such as veins. Subsequently, their performance is explored in a clinically relevant scenario – the hepatic circulation toward treating primary liver cancer or metastatic nodes of distant tumors (e.g., pancreatic cancer). Computational fluid dynamics analyses using the data from five different patients demonstrate that robust navigation can be achieved with high actuation frequencies. Overall, the findings presented in this study lay a preliminary foundation for the potential future application of surface microrollers in vivo.

In the natural world, microorganisms constantly navigate through confined spaces—such as those found in tissues, biological gels, and soil—yet their behavior in such environments remains poorly understood. Here, we explore this phenomenon by examining the navigation of magnetic microalgal biohybrids in constrained microenvironments. By leveraging the inherent propulsion of green microalgae and external steering capabilities acquired through the magnetization of microalgal cells, our biohybrids exhibit efficient navigation in viscous and confined microenvironments. Through high-yield fabrication and magnetic manipulation, we show precise control over their movement. Our findings reveal distinct navigation patterns influenced by magnetic guidance, namely backtracking and crossing, shedding light on the unexplored dynamics of confined locomotion assisted by magnetism. Our work highlights the significance of understanding microalgal biohybrid swimming behavior, offering crucial insights for future biotechnological and biomedical applications requiring precise navigation in confined environments.

Wireless neuromodulation techniques are widely investigated to address the challenges associated with conventional neurostimulation devices. Previous research has relied on ultrasound, light and magnetic fields as the modalities for remotely powering neuronal implants. Use of magnetic fields has been promising for wireless neuronal interfaces since they have excellent tissue penetration. Magnetically powered devices typically work with >100 kHz electromagnetic fields; therefore, they are heavily dependent on the on-board electronics to regulate output signal. Moreover, use of such high frequency is a limiting factor for safe use, especially in deeper areas due to tissue absorption. Magnetoelectric (ME) approach is a promising method that stems from the magneto-electrical coupling. It is a high throughput approach for power delivery through magnetic fields in low frequency regimes compared to far-field or inductive coupling. In this study, we aim to understand how ME approach can be used to modulate neuronal behavior in non-resonant frequency regimes. We fabricated ME planar films through laminating magnetostrictive and piezoelectric components. We initially defined the output electrical potential as the main design parameter and subsequently optimize the device geometry and applied magnetic field profile to achieve the best possible performance. We were able to observe current density of ∼ 4-6 μA/cm2 in phosphate-buffered saline environment under 10 Hz input magnetic field. Lastly, we investigated neuromodulation potential of the ME films in-vitro through calcium imaging studies. Our preliminary results show that primary hippocampal neurons have significantly increased calcium influx during stimulation compared to pre-stimulation phase. Stimulation efficiency was further investigated with changing stimulation duration and input magnetic field waveforms. Overall, these results show that ME films are promising candidates of neuronal interfaces for wireless electrical modulation. Future work will be conducted to understand exact mechanisms of neuromodulation and design such interfaces in an implantable miniature form for in-vivo studies.

The objective of this work was to print nanoparticle-added photothermoresponsive hydrogels to remove the drawbacks of photothermal therapy (PTT), which is a substitute for conventional cancer treatment. For printing hydrogels (LIHAM) via N-isopropylacrylamide (NIPAM), polyethylene glycol, green synthesized gold nanoflowers (AuNPs) coated with rose bengal (RB) as a photosensitizer, and polydopamine (PDA) as photoinitiator material were used. The printing procedure for the meta-structure, which was designed as 20 × 2 mm using the 3DS Max Autodesk Software, was carried out with the microArch S240 BMF PμSL 3D printer. Additionally, the intensity of light was 60 lm, and the exposure printer time was 8–6–6–6–4 s for this research article. Five different photosensitive hydrogels were printed for rheological measurements, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, differential scanning calorimetry, and hyperthermia analysis. This study also aims to demonstrate that the kirigami LIHAM hydrogel can change shape by doping with AuNPs@PDA@RB exclusively under 565 nm without the need for a heater. The results indicated that the greatest outcomes in terms of mechanical, rheological, chemical, and thermal properties and printability were obtained with LIHAM hydrogels coated with AuNPs@PDA@RB. As a result, it has been seen that the LIHAM hydrogels coated with green synthesized gold nanoflowers can be produced with a 3D printer in microsized and complex structures and can be used in hyperthermia applications in the future.

Acoustic waves provide a biocompatible and deep-tissue-penetrating tool suitable for contactless manipulation in in vivo environments. Despite the prevalence of dynamic fluids within the body, previous studies have primarily focused on static fluids, and manipulatable agents in dynamic fluids are limited to gaseous core-shell particles. However, these gas-filled particles face challenges in fast-flow manipulation, complex setups, design versatility, and practical medical imaging, underscoring the need for effective alternatives. In this study, flower-like hierarchical nanostructures (HNS) into microparticles (MPs) are incorporated, and demonstrated that various materials fabricated as HNS-MPs exhibit effective and reproducible acoustic trapping within high-velocity fluid flows. Through simulations, it is validated that the HNS-MPs are drawn to the focal point by acoustic streaming and form a trap through secondary acoustic streaming at the tips of the nanosheets comprising the HNS-MPs. Furthermore, the wide range of materials and modification options for HNS, combined with their high surface area and biocompatibility, enable them to serve as acoustically manipulatable multimodal imaging contrast agents and microrobots. They can perform intravascular multi-trap maneuvering with real-time imaging, purification of wastewater flow, and highly-loaded drug delivery. Given the diverse HNS materials developed to date, this study extends their applications to acoustofluidic and biomedical fields.

We develop a simple model of ionic current through neuronal membranes as a function of membrane potential and extracellular ion concentration. The model combines a simplified Poisson–Nernst–Planck (PNP) model of ion transport through individual ion channels with channel activation functions calibrated from ad hoc in-house experimental data. The simplified PNP model is validated against bacterial gramicidin A ion channel data. The calibrated model accounts for the transport of calcium, sodium, potassium, and chloride and exhibits remarkable agreement with the experimentally measured current–voltage curves for the differentiated human neural cells.

Small-scale wireless soft robotics can be designed as implantable, interventional or wearable devices for various biomedical applications. Their flexibility, dexterity, adaptability and safe interactions with biological environments make them promising candidates for enabling precise and remote healthcare and disease diagnosis. However, the clinical translation of wireless soft robotic medical devices remains challenging. In this Review, we provide a comprehensive overview of the robotic technologies, the navigation methods, the dexterous functions and the translational challenges of wireless soft robotic medical devices. We first discuss safety and biocompatibility from a biological and technical perspective and then examine navigation methods for overcoming biological barriers for delivery, mobility and retrieval, highlighting dexterous medical functions at small scales. Finally, we identify key product development challenges, as well as the regulatory and ethical considerations that should be addressed to enable the clinical translation of wireless soft robotic medical devices.

Electrical stimulation is a fundamental tool in studying neural circuits, treating neurological diseases, and advancing regenerative medicine. Injectable, free-standing piezoelectric particle systems have emerged as non-genetic and wireless alternatives for electrode-based tethered stimulation systems. However, achieving cell-specific and high-frequency piezoelectric neural stimulation remains challenging due to high-intensity thresholds, non-specific diffusion, and internalization of particles. Here, we develop cell-sized 20 μm-diameter silica-based piezoelectric magnetic Janus microparticles (PEMPs), enabling clinically-relevant high-frequency neural stimulation of primary neurons under low-intensity focused ultrasound. Owing to its functionally anisotropic design, half of the PEMP acts as a piezoelectric electrode via conjugated barium titanate nanoparticles to induce electrical stimulation, while the nickel-gold nanofilm-coated magnetic half provides spatial and orientational control on neural stimulation via external uniform rotating magnetic fields. Furthermore, surface functionalization with targeting antibodies enables cell-specific binding/targeting and stimulation of dopaminergic neurons. Taking advantage of such functionalities, the PEMP design offers unique features towards wireless neural stimulation for minimally invasive treatment of neurological diseases.

With wireless multimodal locomotion capabilities, magnetic soft millirobots have emerged as potential minimally invasive medical robotic platforms. Due to their diverse shape programming capability, they can generate various locomotion modes, and their locomotion can be adapted to different environments by controlling the external magnetic field signal. Existing adaptation methods, however, are based on hand-tuned signals. Here, a learning-based adaptive magnetic soft millirobot multimodal locomotion framework empowered by sim-to-real transfer is presented. Developing a data-driven magnetic soft millirobot simulation environment, the periodic magnetic actuation signal is learned for a given soft millirobot in simulation. Then, the learned locomotion strategy is deployed to the real world using Bayesian optimization and Gaussian processes. Finally, automated domain recognition and locomotion adaptation for unknown environments using a Kullback-Leibler divergence-based probabilistic method are illustrated. This method can enable soft millirobot locomotion to quickly and continuously adapt to environmental changes and explore the actuation space for unanticipated solutions with minimum experimental cost.

Medical microrobotics is an emerging field to revolutionize clinical applications in diagnostics and therapeutics of various diseases. On the other hand, the mobile microrobotics field has important obstacles to pass before clinical translation. This article focuses on these challenges and provides a roadmap of medical microrobots to enable their clinical use. From the concept of a “magic bullet” to the physicochemical interactions of microrobots in complex biological environments in medical applications, there are several translational steps to consider. Clinical translation of mobile microrobots is only possible with a close collaboration between clinical experts and microrobotics researchers to address the technical challenges in microfabrication, safety, and imaging. The clinical application potential can be materialized by designing microrobots that can solve the current main challenges, such as actuation limitations, material stability, and imaging constraints. The strengths and weaknesses of the current progress in the microrobotics field are discussed and a roadmap for their clinical applications in the near future is outlined.

Stimuli-responsive soft robots offer new capabilities for the fields of medical and rehabilitation robotics, artificial intelligence, and soft electronics. Precisely programming the shape morphing and decoupling the multiresponsiveness of such robots is crucial to enable them with ample degrees of freedom and multifunctionality, while ensuring high fabrication accuracy. However, current designs featuring coupled multiresponsiveness or intricate assembly processes face limitations in executing complex transformations and suffer from a lack of precision. Therefore, we propose a one-stepped strategy to program multistep shape-morphing soft millirobots (MSSMs) in response to decoupled environmental stimuli. Our approach involves employing a multilayered elastomer and laser scanning technology to selectively process the structure of MSSMs, achieving a minimum machining precision of 30 μm. The resulting MSSMs are capable of imitating the shape morphing of plants and hand gestures and resemble kirigami, pop-up, and bistable structures. The decoupled multistimuli responsiveness of the MSSMs allows them to conduct shape morphing during locomotion, perform logic circuit control, and remotely repair circuits in response to humidity, temperature, and magnetic field. This strategy presents a paradigm for the effective design and fabrication of untethered soft miniature robots with physical intelligence, advancing the decoupled multiresponsive materials through modular tailoring of robotic body structures and properties to suit specific applications.

Wireless millimeter-scale robots capable of navigating through fluid-flowing tubular structures hold substantial potential for inspection, maintenance, or repair use in nuclear, industrial, and medical applications. However, prevalent reliance on external powering constrains these robots’ operational range and applicable environments. Alternatives with onboard powering must trade off size, functionality, and operation duration. Here, we propose a wireless millimeter-scale wheeled robot capable of using environmental flows to power and actuate its long-distance locomotion through complex pipelines. The flow-powering module can convert flow energy into mechanical energy, achieving an impeller speed of up to 9595 revolutions per minute, accompanied by an output power density of 11.7 watts per cubic meter and an efficiency of 33.7%. A miniature gearbox module can further transmit the converted mechanical energy into the robot’s locomotion system, allowing the robot to move against water flow at an average rate of up to 1.05 meters per second. The robot’s motion status (moving against/with flow or pausing) can be switched using an external magnetic field or an onboard mechanical regulator, contingent on different proposed control designs. In addition, we designed kirigami-based soft wheels for adaptive locomotion. The robot can move against flows of various substances within pipes featuring complex geometries and diverse materials. Solely powered by flow, the robot can transport cylindrical payloads with a diameter of up to 55% of the pipe’s diameter and carry devices such as an endoscopic camera for pipeline inspection, a wireless temperature sensor for environmental temperature monitoring, and a leak-stopper shell for infrastructure maintenance.

Underwater devices are critical for environmental applications. However, existing prototypes typically use bulky, noisy actuators and limited configurations. Consequently, they struggle to ensure noise-free and gentle interactions with underwater species when realizing practical functions. Therefore, we developed a jellyfish-like robotic platform enabled by a synergy of electrohydraulic actuators and a hybrid structure of rigid and soft components. Our 16-cm-diameter noise-free prototype could control the fluid flow to propel while manipulating objects to be kept beneath its body without physical contact, thereby enabling safer interactions. Its against-gravity speed was up to 6.1 cm/s, substantially quicker than other examples in literature, while only requiring a low input power of around 100 mW. Moreover, using the platform, we demonstrated contact-based object manipulation, fluidic mixing, shape adaptation, steering, wireless swimming, and cooperation of two to three robots. This study introduces a versatile jellyfish-like robotic platform with a wide range of functions for diverse applications.