Microrobotic System Research Articles

Micro-robotic percutaneous targeting of type II endoleaks in the angio-suite

PurposeEndovascular aneurysm repair has emerged as the standard therapy for abdominal aortic aneurysms. In 9–30% of cases, retrograde filling of the aneurysm sac through patent branch arteries may result in persistence of blood flow outside the graft and within the aneurysm sac. This condition is called an endoleak type II, which may be treated by catheter-based embolization in case of continued sac enlargement. If an endovascular access is not possible, percutaneous targeting of the perfused nidus remains the only option. However, this can be very challenging due to the difficult access and deep puncture with risk of organ perforation and bleeding. Innovative targeting techniques such as robotics may provide a promising option for safe and successful targeting.MethodsIn nine consecutive patients, percutaneous embolization of type II endoleaks was performed using a table-mounted micro-robotic targeting platform. The needle path from the skin entry to the perfused nidus was planned based on the C-arm CT image data in the angio-suite. Entry point and path angle were aligned using the joystick-operated micro-robotic system under fluoroscopic control, and the coaxial needle was introduced until the target point within the perfused nidus was reached.ResultsAll punctures were successful, and there were no puncture-related complications. The pre-operative C-arm CT was executed in 11–15 s, and pathway planning required 2–3 min. The robotic setup and sterile draping were performed in 1–2 min, and the alignment to the surgical plan took no longer than 30 s.ConclusionDue to the small size, the micro-robotic platform seamlessly integrated into the routine clinical workflow in the angio-suite. It offered significant benefits to the planning and safe execution of double-angulated deeply localized targets, such as type II endoleaks.

Engineered Microrobots for Targeted Delivery of Bacterial Outer Membrane Vesicles (OMV) in Thrombus Therapy.

In the realm of thrombosis treatment, bioengineered outer membrane vesicles (OMVs) offer a novel and promising approach, as they have rich content of bacterial-derived components. This study centers on OMVs derived from Escherichia coli BL21 cells, innovatively engineered to encapsulate the staphylokinase-hirudin fusion protein (SFH). SFH synergizes the properties of staphylokinase (SAK) and hirudin (HV) to enhance thrombolytic efficiency while reducing the risks associated with re-embolization and bleeding. Building on this foundation, this study introduces two cutting-edge microrobotic platforms: SFH-OMV@H for venous thromboembolism (VTE) treatment, and SFH-OMV@MΦ, designed specifically for cerebral venous sinus thrombosis (CVST) therapy. These platforms have demonstrated significant efficacy in dissolving thrombi, with SFH-OMV@H showcasing precise vascular navigation and SFH-OMV@MΦ effectively targeting cerebral thrombi. The study shows that the integration of these bioengineered OMVs and microrobotic systems marks a significant advancement in thrombosis treatment, underlining their potential to revolutionize personalized medical approaches to complex health conditions.

Efficient Energy Management for Intelligent Microrobotic Swarms: Design and Impact

AbstractEnergy serves as the foundational element for all active functions within microrobots. Harvesting devices, such as photovoltaic cells and coils, play a crucial role in converting diverse forms of energy into electricity, while energy storage devices enable uninterrupted operation and liberate microrobots from dependence on external sources. Despite the evident importance of energy, there exists a significant disconnect between the development of energy devices and their integration into microrobotic systems, hampering the deployment of microrobots across diverse fields from agriculture to microsurgery. Here, for transcending the “material for material's sake” focus on simple generic metrics for material optimization, such as energy density, advocating attention to the higher tier transformation of material metrics that determine device‐level performance and so make a meaningful contribution to microrobotic technology is argued. Appropriate metrics for microrobotic swarms challenge the stereotype that tiny energy supplies are impractical; instead, swarms simplify individual microrobotic functions, reducing single energy supply requirements and utilizing swarm energy distribution and management. In addition to essential evaluations of the environmental and social impacts of intelligent microrobotic swarms for their safe and beneficial implementation, research targeting these higher‐tier metrics is crucial to connecting energy material research and microrobot developments effectively.

An Overview of Microrobotic Systems for Microforce Sensing

Considering microbotics, microforce sensing, their working environment, and their control architecture together, microrobotic force-sensing systems provide the potential to outperform traditional stand-alone approaches. Microrobotics is a unique way for humans to control interactions between a robot and micrometer-size samples by enabling the control of speeds, dynamics, approach angles, and localization of the contact in a highly versatile manner. Many highly integrated microforce sensors attempt to measure forces occurring during these interactions, which are highly difficult to predict because the forces strongly depend on many environmental and system parameters. This article discusses state-of-the-art microrobotic systems for microforce sensing, considering all of these factors. It starts by presenting the basic principles of microrobotic microforce sensing, robotics, and control. It then discusses the importance of microforce sensor calibration and active microforce-sensing techniques. Finally, it provides an overview of microrobotic microforce-sensing systems and applications, including both tethered and untethered microrobotic approaches.

Automating Robotic Micro-Assembly of Fluidic Chips and Single Fiber Compression Tests Based-on Θ Visual Measurement With High-Precision Fiducial Markers

At small scales, automating robotic tasks such as assembly, force/displacement characterization, positioning, etc., appear to be particularly limited. This is due to the lack of sufficiently performing and easy-to-implement multi-degrees-of-freedom measurement systems able to measure the relative pose between micro-parts. In order to address this issue, a measurement method based on High-Precision fiducial markers (named HP code) is proposed. This measurement method combines a periodic pattern (providing high resolution by phase-based computation) with more regular QR codes (bringing versatile implementations and a quick detection). The design and method to efficiently locate these HP codes are presented in this paper. Experimental investigations demonstrate ultra-high resolution: <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2$</tex-math> </inline-formula> nm and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5$</tex-math> </inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\upmu$</tex-math> </inline-formula> rad along <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$X,Y$</tex-math> </inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Theta$</tex-math> </inline-formula> respectively (i.e. one thousandth of a pixel typically). The method is designed to be scalable as well as self-calibrated and to provide high robustness and high versatility. Two typical challenging applications in the field of microrobotics are automated to demonstrate these disruptive performances and the easy-to-implement capability of the method: (1) the automated assembly of two micro-fluidic chips through visual servoing with an achieved positioning accuracy below <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50$</tex-math> </inline-formula> nm, and (2) the automated micromechanical characterization of single fibers achieved by the integration of HP codes into a compliant structure enabling simultaneous micro-force and displacement sensing capabilities. These achievements highlight the versatility of the method and open the door to the rapid automation of high-quality robotic tasks at the micro scale. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —The motivation for this work/study is based on the fact that many application areas are extensively orienting towards microrobotic systems to perform precise tasks with versatility. However, at the micro scale, many disturbances such as the effects of climate change strongly affect this precision. This problem is amplified by the fact that sensors cannot be easily integrated, either by lack of space or by the lack of measurement systems available. Vision-based approaches are widespread at this scale and appear very promising to measure the relative pose between micro-parts. Nevertheless, existing vision-based approaches like digital image correlation are both scale and texture dependent. Due to the lack of space, they are also difficult to use in practice at small scales for high resolution measurement. The main contribution of this paper lies in the capability to achieve ultra-high resolution measurements. For that, a structure based on High-Precision fiducial markers (named HP codes) is proposed and requires few and simple settings while achieving very high resolution both in position and orientation, typically down to one thousandth of a pixel and a few micro radians, respectively. It provides an off-the-shelf solution, versatile, easy to implement and achieves high resolution measurements in the plane (XY <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Theta$</tex-math> </inline-formula> ). HP codes are applicable to a wide range of applications such as tracking of a component/part of a mobile or deformable system, visual servoing of microrobots, positioning of samples, assembly of components or even mechanical characterization. A free distribution of the library is available online at https://projects.femto-st.fr/ vernier/.

A NIR-driven green affording-oxygen microrobot for targeted photodynamic therapy of tumors.

Photodynamic therapy (PDT) is a light-activated local treatment modality that has promising potential in cancer therapy. However, ineffective delivery of photosensitizers and hypoxia in the tumor microenvironment severely restrict the therapeutic efficacy of PDT. Herein, phototactic Chlorella (C) is utilized to carry photosensitizer-encapsulated nanoparticles to develop a near-infrared (NIR) driven green affording-oxygen microrobot system (CurNPs-C) for enhanced PDT. Photosensitizer (curcumin, Cur) loaded nanoparticles are first synthesized and then covalently attached to C through amide bonds. An in vitro study demonstrates that the developed CurNPs-C exhibits continuous oxygen generation and desirable phototaxis under NIR treatment. After intravenous injection, the initial 660 nm laser irradiation successfully induces the active migration of CurNPs-C to tumor sites for higher accumulation. Upon the second 660 nm laser treatment, CurNPs-C produces abundant oxygen, which in turn induces the natural product Cur to generate more reactive oxygen species (ROS) that significantly inhibit the growth of tumors in 4T1 tumor-bearing mice. This contribution showcases the ability of a light-driven green affording-oxygen microrobot to exhibit targeting capacity and O2 generation for enhancing photodynamic therapy.

Magnetically Manipulated Optoelectronic Hybrid Microrobots for Optically Targeted Non-Genetic Neuromodulation.

Optically controlled neuromodulation is a promising approach for basic research of neural circuits and the clinical treatment of neurological diseases. However, developing a non-invasive and well-controllable system to deliver accurate and effective neural stimulation is challenging. Micro/nanorobots have shown great potential in various biomedical applications because of their precise controllability. Here, a magnetically-manipulated optoelectronic hybrid microrobot (MOHR) is presented for optically targeted non-genetic neuromodulation. By integrating the magnetic component into the metal-insulator-semiconductor junction design, the MOHR has excellent magnetic controllability and optoelectronic properties. The MOHR displays a variety of magnetic manipulation modes that enables precise and efficient navigation in different biofluids. Furthermore, the MOHR could achieve precision neuromodulation at the single-cell level because of its accurate targeting ability. This neuromodulation is achieved by the MOHR's photoelectric response to visible light irradiation, which enhances the excitability of the targeted cells. Finally, it is shown that the well-controllable MOHRs effectively restore neuronal activity in neurons damaged by β-amyloid, a pathogenic agent of Alzheimer's disease. By coupling precise controllability with efficient optoelectronic properties, the hybrid microrobot system is a promising strategy for targeted on-demand optical neuromodulation.

Biohybrid Microalgae Robots: Design, Fabrication, Materials, and Applications.

The integration of microorganisms and engineered artificial components has shown considerable promise for creating biohybrid microrobots. The unique features of microalgae make them attractive candidates as natural actuation materials for the design of biohybrid microrobotic systems. In this review, microalgae-based biohybrid microrobots are introduced for diverse biomedical and environmental applications. The distinct propulsion and phototaxis behaviors of green microalgae, as well as important properties from other photosynthetic microalga systems (blue-green algae and diatom) that are crucial to constructing powerful biohybrid microrobots, will be described first. Then the focus is on chemical and physical routes for functionalizing the algae surface with diverse reactive materials toward the fabrication of advanced biohybrid microalgae robots. Finally, representative applications of such algae-driven microrobots are presented, including drug delivery, imaging, and water decontamination, highlighting the distinct advantages of these active biohybrid robots, along with future prospects and challenges.

Nonlinear time-frequency iterative learning control for micro-robotic deposition system using adaptive Fourier decomposition approach

Nonlinear time-frequency iterative learning control for micro-robotic deposition system using adaptive Fourier decomposition approach

Collaborative Magnetic Agents for 3D Microrobotic Grasping

Untethered microrobotic grasping has enabled the precise manipulation of small components in difficult‐to‐reach environments. However, the fabrication of deformable grasping robots at small scales requires advanced materials and fabrication technologies. Alternatively, multiple microrobots can be used to surround and grasp objects. By collaborating, microrobots can perform complex tasks that they would not be capable of executing individually. The complexity of controlling multiple untethered microrobots has limited the applications of collaborative microrobots to two‐dimensional operations. To fill this gap, this work proposes a collaborative microrobotic system for three‐dimensional grasping operations. The system is based on the control of two magnetic agents and the exploitation of the magnetic interactions between them to grasp, manipulate, and assemble passive components. A custom‐made closed‐loop controller is developed to automatically stabilize the system, achieving pose control of a grasped passive component (of 2 mm in size) with a precision of 300 μm in position and 10° in orientation. The main advantage of the proposed system is its capability to reconfigure the magnetic agents for other operations, as demonstrated by the assembly of a microgear and subsequent reconfiguration to power the assembled mechanism.

Towards multifunctional robotic pills.

Robotic pills leverage the advantages of oral pharmaceutical formulations-in particular, convenient encapsulation, high loading capacity, ease of manufacturing and high patient compliance-as well as the multifunctionality, increasing miniaturization and sophistication of microrobotic systems. In this Perspective, we provide an overview of major innovations in the development of robotic pills-specifically, oral pills embedded with robotic capabilities based on microneedles, microinjectors, microstirrers or microrockets-summarize current progress and applicational gaps of the technology, and discuss its prospects. We argue that the integration of multiple microrobotic functions within oral delivery systems alongside accurate control of the release characteristics of their payload provides a basis for realizing sophisticated multifunctional robotic pills that operate as closed-loop systems.

Light-Powered Self-Adaptive Mesostructured Microrobots for Simultaneous Microplastics Trapping and Fragmentation via in situ Surface Morphing.

Microplastics, which comprise one of the omnipresent threats to human health, are diverse in shape and composition. Their negative impacts on human and ecosystem health provide ample incentive to design and execute strategies to trap and degrade diversely structured microplastics, especially from water. This work demonstrates the fabrication of single-component TiO2 superstructured microrobots to photo-trap and photo-fragment microplastics. In a single reaction, rod-like microrobots diverse in shape and with multiple trapping sites, are fabricated to exploit the asymmetry of the microrobotic system advantageous for propulsion. The microrobots work synergistically to photo-catalytically trap and fragment microplastics in water in a coordinated fashion. Hence, a microrobotic model of "unity in diversity" is demonstrated here for the phototrapping and photofragmentation of microplastics. During light irradiation and subsequent photocatalysis, the surface morphology of microrobots transformed into porous flower-like networks that trap microplastics for subsequent degradation. This reconfigurable microrobotic technology represents a significant step forward in the efforts to degrade microplastics.

Reconfigurable Liquid‐Bodied Miniature Machines: Magnetic Control and Microrobotic Applications

Soft miniature machines demonstrate multimodal actuation and morphology change capabilities in narrow spaces smaller than their dimension. The wirelessly controlled soft‐bodied features make them promising candidates for microrobotic manipulation and targeted operation in a noninvasive manner. Liquid‐bodied machine offers an ultrasoft body with extreme deformability owing to its fluid nature, enabling adaptive navigation with smooth contact with objects and environmental restrictions. Over the last decade of development, significant research progress has been achieved in wirelessly controlling liquid‐bodied machines for diverse manipulation applications. Herein, an overview of the recent research results in magnetic control methods and diverse microrobotic applications of liquid‐bodied machines is provided. Considering the control mechanisms and application challenges, ferrofluid‐based, liquid metal‐based, and liquid marble‐based machines are mainly discussed with a brief discussion on droplet‐based machines. The connection between control methods and applications is highlighted with a detailed analysis of machine–object and machine–environment interactions. The current challenges and research opportunities on liquid‐bodied miniature machines are outlined, aiming at designing intelligent liquid‐bodied machine‐based microrobotic systems and promoting the development of small‐scale robotics.

Two-Degree-of-Freedom Control of a Micro-Robot Using a Dual-Rate State Observer

This brief presents a novel tracking control algorithm for a micro-robot based on dynamics and positional measurements. The algorithm improves the tracking performance and response time. We designed a two-degree-of-freedom (TDOF) control, which is widely utilized in industrial servo systems, for a micro-robot. Our TDOF control prevents undesirable effects, such as model uncertainty. The dynamic characteristics of a micro-robot were analyzed using the frequency response function (FRF), and a dynamic model specific for micro-robot motion was derived. This brief also addresses the dual-rate problem of micro-robot control systems by designing a dual-rate state observer (DSO) that provides positional information for the micro-robot when no camera updates are available. Thus, the TDOF controller provides feedback control at higher sampling frequencies. The performance of the controller was experimentally verified.

Horizontal and Vertical Coalescent Microrobotic Collectives Using Ferrofluid Droplets.

Many artificial miniature robotic collectives have been developed to overcome the inherent limitations of inadequate individual capabilities. However, the basic building blocks of the reported collectives are mainly in the solid state, where the morphological boundaries of internal individuals are clear and cannot genuinely merge. Miniature robotic collectives based on liquid units still need to be explored; such on-demand mergeable swarm systems are advantageous for adapting to the changing external environment. Here, a strategy to achieve a coalescent collective system wepresented that exploits the ferrofluid droplets' splitting and coalescence properties to trigger the formation of horizontal multimodal and vertical gravity-resistant collectives and unveil pattern-enabled robotic functionalities. When subjected to a time-varying magnetic field, the droplet swarm exhibits a variety of morphologies ranging from horizontal collectives, including vortex-like, chain-like, and crystal-like patterns to vertical layer-upon-layer patterns. Using experiments and simulations, the formation and transformation of different morphological collectives are shown and their robust environmental adaptability are demonstrated. Potential applications of the multimodal droplet collectives are presented, including exploring an unknown environment, targeted object delivery, and fluid flow filtration in a lab-on-a-chip. This work may facilitate the design of microrobotic swarm systems and expand the range of materials for miniature robots.

Three-Dimensionally Complex Phase Behavior and Collective Phenomena in Mixtures of Acoustically Powered Chiral Microspinners.

The process of dynamic self-organization of small building blocks is fundamental to the emergent function of living systems and is characteristic of their out-of-equilibrium homeostasis. The ability to control the interactions of synthetic particles in large groups could lead to the realization of analogous macroscopic robotic systems with microscopic complexity. Rotationally induced self-organization has been observed in biological systems and modeled theoretically, but studies of fast, autonomously moving synthetic rotors remain rare. Here, we report switchable, out-of-equilibrium hydrodynamic assembly and phase separation in suspensions of acoustically powered chiral microspinners. Semiquantitative modeling suggests that three-dimensionally (3D) complex spinners interact through viscous and weakly inertial (streaming) flows. The interactions between spinners were studied over a range of densities to construct a phase diagram, which included gaseous dimer pairing at low density, collective rotation and multiphase separation at intermediate densities, and ultimately jamming at high density. The 3D chirality of the spinners leads to self-organization in parallel planes, forming a three-dimensionally hierarchical system that goes beyond the 2D systems that have so far been modeled computationally. Dense mixtures of spinners and passive tracer particles also show active-passive phase separation. These observations are consistent with recent theoretical predictions of the hydrodynamic coupling between rotlets generated by autonomous spinners and provide an exciting experimental window to the study of colloidal active matter and microrobotic systems.

Mobile mechanical signal generator for macrophage polarization.

The importance of mechanical signals in regulating the fate of macrophages is gaining increased attention recently. However, the recently used mechanical signals normally rely on the physical characteristics of matrix with non-specificity and instability or mechanical loading devices with uncontrollability and complexity. Herein, we demonstrate the successful fabrication of self-assembled microrobots (SMRs) based on magnetic nanoparticles as local mechanical signal generators for precise macrophage polarization. Under a rotating magnetic field (RMF), the propulsion of SMRs occurs due to the elastic deformation via magnetic force and hydrodynamics. SMRs perform wireless navigation toward the targeted macrophage in a controllable manner and subsequently rotate around the cell for mechanical signal generation. Macrophages are eventually polarized from M0 to anti-inflammatory related M2 phenotypes by blocking the Piezo1-activating protein-1 (AP-1）-CCL2 signaling pathway. The as-developed microrobot system provides a new platform of mechanical signal loading for macrophage polarization, which holds great potential for precise regulation of cell fate.

Assembly of Fillable Microrobotic Systems by Microfluidic Loading with Dip Sealing.

Microrobots can provide spatiotemporally well-controlled cargo delivery that can improve therapeutic efficiency compared to conventional drug delivery strategies. Robust microfabrication methods to expand the variety of materials or cargoes that can be incorporated into microrobots can greatly broaden the scope of their functions. However, current surface coating or direct blending techniques used for cargo loading result in inefficient loading and poor cargo protection during transportation, which leads to cargo waste, degradation and non-specific release. Herein, a versatile platform to fabricate fillable microrobots using microfluidic loading and dip sealing (MLDS) is presented. MLDS enables the encapsulation of different types of cargoes within hollow microrobots and protection of cargo integrity. The technique is supported by high-resolution 3D printing with an integrated microfluidic loading system, which realizes a highly precise loading process and improves cargo loading capacity. A corresponding dip sealing strategy is developed to encase and protect the loaded cargo whilst maintaining the geometric and structural integrity of the loaded microrobots. This dip sealing technique is suitable for different materials, including thermal and light-responsive materials. The MLDS platform provides new opportunities for microrobotic systems in targeted drug delivery, environmental sensing, and chemically powered micromotor applications.

Multi-Wavelength Light-Responsive Metal-Phenolic Network-Based Microrobots for Reactive Species Scavenging.

Light-driven microrobots with different propulsion mechanisms have attracted great attention in microrobot synthesis and applications. However, current systems rely heavily on precious metals, using a complex synthesis process and limited working wavelength. It is therefore of great interest to fabricate microrobots that can be driven by multi-wavelength irradiation and with simple components. Here, metal-phenolic network (MPN)-based microrobots are synthesized using a sacrificial polystyrene bead template and an extra capping is added to regulate their symmetry. The hollow MPN microrobots with different layers of capping are capable of moving under both near-infrared (NIR) irradiation and ultraviolet (UV) irradiation, without fuel. The velocity of the microrobots under irradiation is altered by the thickness of the asymmetric capping and their motion could be manipulated remotely by switching the NIR or UV irradiation on and off. With light-driven mobility, the reactive oxygen and nitrogen species (RONS) scavenging activity of the microrobots is significantly increased. Therefore, this proposed microrobot system provides a synthesis strategy to develop asymmetric light-navigated microrobots for future medical treatment with tunable structure, multi-wavelength light-responsive mobility, and great RONS scavenging capacity.

Nonlinear tracking differentiator and PD controller for piezoelectric actuators in a robotic hand

This article deals with the modeling and control design for piezoelectric actuators of a micro-robotic system. Piezoelectric actuators generally exhibit complex and nonlinear behavior due to their inherent asymmetric hysteresis phenomenon, creep nonlinearity, and oscillatory characteristics. Moreover, these actuators are subject to an external disturbance force caused by the interaction with the manipulated objects. It has been shown in practice that these characteristics have a negative and significant impact on the performance of piezoelectric actuators, which increases the difficulty of their control. The main objective of this paper is to account simultaneously for all undesired and complex characteristics outlined above. To this end, our main idea is to lump the hysteresis and creep phenomena, as well as the disturbing manipulation force together as one total disturbance term. The total disturbance is first estimated in real-time via a nonlinear tracking differentiator, then feedback control law is designed to compensate for the disturbance and achieve a good transient profile. To validate and demonstrate the efficacy of the proposed approach, experiments are conducted, and results obtained are discussed.