Publications

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.