Actuation-enhanced multifunctional sensing and information recognition by magnetic artificial cilia arrays

Ultrasound-activated cilia for biofilm control in indwelling medical devices

Biofilm formation and encrustation are major issues in indwelling medical devices, such as urinary stents and catheters, as they lead to blockages and infections. Currently, to limit these effects, frequent replacements of these devices are necessary, resulting in a significant reduction in patients' quality of life and an increase in healthcare costs. To address these challenges, by leveraging recent advancements in robotics and microfluidic technologies, we envision a self-cleaning system for indwelling medical devices equipped with bioinspired ultrasound-activated cilia. These cilia could be regularly activated transcutaneously by ultrasound, generating steady streaming, which can be used to remove encrusted deposits. In this study, we tested the hypothesis that the generated streaming can efficiently remove encrustations and biofilm from surfaces. To this end, we developed a microfluidic model featuring ultrasound-activated cilia on its wall. We showed that upon ultrasound activation, the cilia generated intense, steady streaming, reaching fluid velocity up to 10 mm/s. In all our experiments, this mechanism was able to efficiently clean typical encrustation (calcium carbonate and oxalate) and biofilm found in urological devices. The generated shear forces released, broke apart, and flushed away encrusted deposits. These findings suggest a broad potential for ultrasound-activated cilia in the maintenance of various medical devices. Compared to existing methods, our approach could reduce the need for invasive procedures, potentially lowering infection risks and enhancing patient comfort.

Surface-Driven Particle Dynamics: Sequential Synchronization of Colloidal Flow Attempted in a Static Fluidic Environment

The collective behavior of colloids in microsystems is characterized by precise micro-object control, broadening the applications of cargo manipulation in drug delivery, microfluidics, and nanotechnology. To further investigate this potential, we introduce a cargo-manipulating platform that utilizes micromagnetic patterns and fluid flow rather than conventional fluidic components. This platform, called the flowless micropump, comprises an encapsulating fluid system within a chip, containing both actuation particles (2.8 μm in diameter) and control targets, thereby eliminating external interactions. This platform enables two distinct modes of cargo manipulation: direct control of nonmagnetic cargo (e.g., MCF-7 and THP-1 cells) and indirect manipulation of particles (e.g., polymer particles) through secondary localized fluid flow. Direct manipulation is achieved via coordinated particle collisions, facilitated by an optimized guiding wall with a height of 25 μm. Conversely, indirect manipulation allows for high-speed control and mode change of individual targets. These manipulation events are achieved using two patterned structures: railway-track and connected half-disk (conductor) patterns. By employing a conductor pattern in conjunction with a railway-track pattern, precise and agile control of microcargo (MCF-7 and THP-1 cells and polymer bead clusters) was achieved at frequencies of 1-3 Hz and a magnetic field strength of 10 mT. This study establishes a programmable platform for designing flowless micropumps with diverse functionalities for various experimental purposes. By using colloidal flow and localized fluid flow generated by the shape of magnetic patterns and semi-three-dimensional (3D) structures, this platform holds significant promise for applications in drug screening, cell-cell interaction studies, and organoid-on-chip research.

Bionic Recognition Technologies Inspired by Biological Mechanosensory Systems

Mechanical information is a medium for perceptual interaction and health monitoring of organisms or intelligent mechanical equipment, including force, vibration, sound, and flow. Researchers are increasingly deploying mechanical information recognition technologies (MIRT) that integrate information acquisition, pre-processing, and processing functions and are expected to enable advanced applications. However, this also poses significant challenges to information acquisition performance and information processing efficiency. The novel and exciting mechanosensory systems of organisms in nature have inspired us to develop superior mechanical information bionic recognition technologies (MIBRT) based on novel bionic materials, structures, and devices to address these challenges. Herein, first bionic strategies for information pre-processing are presented and their importance for high-performance information acquisition is highlighted. Subsequently, design strategies and considerations for high-performance sensors inspired by mechanoreceptors of organisms are described. Then, the design concepts of the neuromorphic devices are summarized in order to replicate the information processing functions of a biological nervous system. Additionally, the ability of MIBRT is investigated to recognize basic mechanical information. Furthermore, further potential applications of MIBRT in intelligent robots, healthcare, and virtual reality are explored with a view to solve a range of complex tasks. Finally, potential future challenges and opportunities for MIBRT are identified from multiple perspectives.

Sensory artificial cilia for in situ monitoring of airway physiological properties

Continuously monitoring human airway conditions is crucial for timely interventions, especially when airway stents are implanted to alleviate central airway obstruction in lung cancer and other diseases. Mucus conditions, in particular, are important biomarkers for indicating inflammation and stent patency but remain challenging to monitor. Current methods, reliant on computational tomography imaging and bronchoscope inspection, pose risks due to radiation and lack the ability to provide continuous real-time feedback outside of hospitals. Inspired by the sensing ability of biological cilia, we report wireless sensing mechanisms in sensory artificial cilia for detecting mucus conditions, including viscosity and layer thickness, which are crucial biomarkers for disease severity. The sensing mechanism for mucus viscosity leverages external magnetic fields to actuate a magnetic artificial cilium and sense its shape using a flexible strain-gauge. Additionally, we report an artificial cilium with capacitance sensing for mucus layer thickness, offering unique self-calibration, adjustable sensitivity, and range, all enabled by external magnetic fields. To enable prolonged and wireless data access, we integrate Bluetooth Low Energy communication and onboard power, along with a wearable magnetic actuation system for sensor activation. We validate our method by deploying the sensor independently or in conjunction with an airway stent within a trachea phantom and sheep trachea ex vivo. The proposed sensing mechanisms and devices pave the way for real-time monitoring of mucus conditions, facilitating early disease detection and providing stent patency alerts, thereby allowing timely interventions and personalized care.

Heterogeneous multiple soft millirobots in three-dimensional lumens

Miniature soft robots offer opportunities for safe and physically adaptive medical interventions in hard-to-reach regions. Deploying multiple robots could further enhance the efficacy and multifunctionality of these operations. However, multirobot deployment in physiologically relevant three-dimensional (3D) tubular structures is limited by the lack of effective mechanisms for independent control of miniature magnetic soft robots. This work presents a framework leveraging the shape-adaptive robotic design and heterogeneous resistance from robot-lumen interactions to enable magnetic multirobot control. We first compute influence and actuation regions to quantify robot movement. Subsequently, a path planning algorithm generates the trajectory of a permanent magnet for multirobot navigation in 3D lumens. Last, robots are controlled individually in multilayer lumen networks under medical imaging. Demonstrations of multilocation cargo delivery and flow diversion manifest their potential to enhance biomedical functions. This framework offers a solution to multirobot actuation benefiting applications across different miniature robotic devices in complex environments.

Flow tweezing of anisotropic magnetic microrobots in a dynamic magnetic trap for active retention and localized flow sensing

Controlled manipulation of microscale robotic devices in complex fluidic networks is critical for various applications in biomedical endovascular sensing, lab-on-chip biochemical assays, and environmental monitoring. However, achieving controlled transport and active retention of microscale robots with flow sensing capability has proven to be challenging. Here, we report the dynamic tweezing of an anisotropic magnetic microrobot in a rotating magnetic trap for active retention and localized flow sensing under confined fluidic conditions. We reveal a series of unconventional motion modes and the dynamics of the microrobot transporting in a confined fluidic flow, which manifest themselves as transitions from on-trap centre rolling to large-area revolution and off-trap centre rolling with varying rotating frequencies. By retaining the robot within the magnetic trap and its motion modulated by the field frequency, the off-centre rolling of the microrobot endows it with crucial localized flow sensing capabilities, including flow rate and flow direction determination. The magnetic microrobot serves as a mobile platform for measuring the flow profile along a curved channel, mimicking a blood vessel. Our findings unlock a new strategy to determine the local magnetic tweezing force profile and flow conditions in arbitrary flow channels, revealing strong potential for microfluidics, chemical reactors, and in vivo endovascular flow measurement.

Single-step precision programming of decoupled multiresponsive soft millirobots

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.