This paper presents a scalable planar electromagnetic actuation platform for independent manipulation of micron-scale microrobots, addressing the limited field strength and scalability of conventional PCB-based electromagnetic systems. The proposed approach utilizes a helically wound copper-foil on a mild steel (MS) core to form a compact 3× 3 electromagnetic coil array, enabling high current operation, rapid prototyping, and flexible scaling while generating strong, spatially localized controllable magnetic field pockets. Finite element modeling analyzes the magnetic field distribution, field gradients, and inter-coil interference, providing quantitative design insight and guiding experimental validation. Magnetic characterization demonstrates peak flux densities of up to 23.73 mT and peak field gradients of approximately 16 T/m at sub-millimeter distances, exceeding typical earlier reported planar electromagnetic coils and enabling precise and repeatable actuation of spherical ferromagnetic microrobots with radii of 100–200 µm. Open-loop experiments in aqueous and viscous media demonstrate spatially selective trapping, translation, and parallel independent actuation of multiple microrobots within distinct workspace regions. The combination of high magnetic field strength, localized actuation, and scalable fabrication establishes the copper-foil electromagnetic coil array as a low-cost and high-performance alternative to existing planar actuation technologies, with direct applicability to high-throughput biological manipulation, micromanufacturing, and microassembly.
Micromanipulation of objects using a magnetic robot is critical for various applications, such as micro-assemblies. However, manipulation skills remain a significant challenge due to the nonlinear interaction between the robot and the object. The effects of pushing can vary from one object to another, depending on how intense the contact is, according to the contact point, surface properties, and so on. This paper presents a pushing controller for micromanipulation using Uncalibrated Visual Servo as robot control. The controller is based on a composite of specific motions or behaviours provided to the robot to maneuver an object. The main advantage of using the proposed controller is its independence from both the robot pusher and object configurations, making it adaptable. Experiments performed on a real system in different scenario show the effectiveness of the proposed controller. The mean absolute error (MAE) is 1.22
Mechanical properties of single cells offer insight into organismal development, disease progression, and mechanotransduction. Yet, estimating the complete mechanical state of single cells, involving multiple parameters, remains challenging due to limited deformation modes available in existing techniques and complex instrumentation. To address this gap, we are developing several compliant micromechanisms that together enable multiple modes of cell manipulation on a single chip. Building on an earlier uniaxial stretcher, here we demonstrate a biaxial stretching mechanism with vision-based force sensing. Because the mechanism uses elastic beams for actuation, stretching forces can be computed from optical displacement measurements using a closed-form analytical model derived from beam theory. This obviates the need for dedicated force sensors thereby simplifying device fabrication and operation. The force displacement relations were validated on macro- and microscale prototypes. The device is microfabricated out of SU-8 using a two-layer photolithography process, yielding an array of miniature stretchers that can be mounted on a coverslip for high-resolution imaging during manipulation. We stretch U87-MG human glioblastoma cells biaxially, compute bulk stiffness, stress and strain in orthogonal directions using microscopy and further fit 2D Fung’s model to investigate anisotropy. This biaxial stretcher can be combined with additional modules (e.g., for shear or twist) to realize a multimodal single-cell mechanophenotyping platform for comprehensive analysis of cellular mechanics. Such a versatile platform represents a new approach to single-cell mechanical characterization.
Magnetic soft elastomers with spatially programmed magnetization profiles can generate complex shape-morphing and locomotion dynamics. Enabled by their unique locomotion capabilities, magnetically programmed soft robots have been proposed for various biomedical applications, including targeted and localized delivery of liquid cargos, such as therapeutic drugs. Current magnetic soft material designs for targeted cargo delivery employ dedicated chambers for loading and integrated valve mechanisms for releasing, which can severely affect the locomotion capabilities or necessitate complicated designs for actuation. Therefore, new strategies are required for incorporating liquid payloads into magnetic soft materials without affecting their locomotion modality, preserving these payloads during transport, and on-demand release via external stimuli once the target location is reached. In this paper, we present magnetic soft elastomers with an interconnected porous internal structure, enabling loading of liquid payloads into the material while preserving magnetic programmability. Furthermore, microcrystalline wax sealing on the outer surface allows locomotion at lower magnetic fields and on-demand seal breaking and releasing of cargos at greater magnetic fields. The cargo loading and on-demand release strategy introduced here enables magnetically co-encoding locomotion and cargo-release and establishes the groundwork for multifunctional magnetic soft materials with potential applications ranging from soft robotics to medical devices and bio interfaces.
This paper presents a novel system for flexible automated fabrication of microrobots with embedded permanent magnets, and for the loading of liquid therapeutic drugs and sealing with thermally sensitive wax. Microrobots featuring embedded magnets are more controllable and observable, and are capable of tasks requiring higher forces. In this system, a micromanipulator controls tweezers, and stepper motors actuate a four-stage system that executes different assembly steps. A syringe pump is used to fill drug delivery microrobots, and a wax seal is applied with a brush made from heated copper wires. This brush is capable of efficiently applying an even wax coating to drug delivery robots, sealing the contained therapeutics inside. Vision-based feedback from an overhead microscope camera ensures precise embedded magnet assembly through a combination of image processing algorithms. A single drug delivery robot can be assembled in 192.77±48.28 seconds (mean±standard deviation, n=13). Drug loading and sealing takes 159.38±3.67 seconds (n=16). 100 μ m (n=16). This work advances micro-assembly toward practical medical use by establishing a practical basis for mass production of drug delivery robots.
Magnetic microrobots are an increasingly popular area of research with a wide range of potential applications including healthcare. These microrobots can be remotely controlled using an external magnetic field to perform various motions such as jumping, swimming, crawling, rolling, and grabbing. This could enable intricate tasks such as drug delivery, stent placements, and wound patching. However, fabricating microrobots is a challenging multi-step process that can take several hours or even days. Therefore, it is important to have an accurate, reproducible, and automated fabrication method. In this work, an existing fully automated stereolithography printer is tested to fabricate magnetic soft robots with voxel sizes smaller than half a millimeter. The work focuses on updating the optics to create a smaller spot size (400 μm ) with more uniform curing distributions using a near ultraviolet beam shaper and a square aperture. The updated optics system in the printer is then used to print a ‛HEART’ sign and five microrobots: a ‛beam’, a ‛gripper’, a ‛pincher’, a ‛crawler’, and a ‛spring cap’, each of which was functionally tested using an externally applied magnetic field.
Wireless capsule endoscopes are often limited to imaging applications and can lack active control capabilities. Over the last two decades, a growing body of research in medical robotics has introduced active actuation. Embedding magnetic components inside these devices is one of the ways to achieve this; however, most of these tools are still limited to a single function, such as drug delivery, sampling, or imaging. Multifunctional capsules capable of performing several tasks can be used for a range of biomedical applications, leading to easy adoption due to their versatility. In this study, we present a novel magnetically actuated capsule with a spring-magnet mechanism designed for drug delivery, microbiome sampling, and cargo transport. The capsule is remotely actuated using external magnetic fields generated by a permanent magnet. It can be activated at a target location for drug delivery, microbiome sampling, or transporting cargo. A mathematical model is developed to optimize the mechanism’s design. We demonstrate the capsule’s multi-functional capabilities through successful drug delivery, sampling, and cargo transport experiments in a 3D printed maze. We also demonstrate capsule navigation in a stomach phantom. This unique mechanism can be adapted and integrated into a range of microrobotic devices, expanding their functionality and clinical utility.
Mechanical properties of cells serve as potential biomarkers for cancer characterization, with different cancer types exhibiting distinct mechanical signatures based on their cytoskeletal organization and membrane properties. This study reports the design and fabrication of a dielectrophoresis (DEP)-based stretching platform for quantitative mechanical phenotyping of cancer cells. The device utilizes transparent indium tin oxide (ITO) electrodes configured as castellated arrays to produce non-uniform electric fields, allowing precise cellular deformation without the need for physical contact or chemical labels. Computational simulations were performed to estimate DEP forces exerted on the cells using the equivalent dipole moment method, revealing quadratic voltage-dependent forces across the experimental range, with maximum forces concentrated at electrode edges. Optimized stretching experiments were conducted on Jurkat (human T-cell leukemia) and SKBR-3 (human breast adenocarcinoma) cells with systematic voltage ramping up to 13 Vp-p. Results demonstrated substantial differences in mechanical response, with Jurkat cells achieving 82.8
Actuation of ball-and-socket joints has been a challenge owing to the multiple degrees of freedom they possess. In the recent past, active ball and socket joints have been proposed but their sizes have generally been large. This paper describes the design and evaluation of a lockable miniaturized ball -and-socket joint. The joint employs a permanent-magnetic sphere seated in a socket, which can be locked magnetically and unlocked by means of dithering. In its locked state, the joint also possesses a high resistance to angular deflections, which is useful for potential biomedical and aerospace applications. Modeling and simulations have been performed in order to confirm that hysteresis can be eliminated by means of dithering. Finally, a miniaturized ball and socket joint with a ball of diameter 5 mm is fabricated and is experimentally demonstrated to achieve much better linearity by applying dithering, with 6-times lesser dead-zone, and negligible hysteresis, in comparison to the case without dithering. Additionally, it is shown that the ball can be locked and unlocked for precise actuation by using the same dithering magnetic field.
This study presents the design, fabrication, and experimental validation of a 3D-printed microgripper based on a compliant mechanism. Compliant mechanisms offer significant advantages over traditional rigid-body designs, including reduced component count, enhanced precision, and improved reliability. The microgripper is designed using SOLIDWORKS and optimized through finite element analysis (FEA) simulations to achieve optimal gripping force and displacement. The structure incorporates flexure hinges and is fabricated using Polyethylene terephthalate glycol (PETG) carbon fiber, a biocompatible and lightweight material. Actuation is achieved using Shape Memory Alloy (SMA) wires, enabling efficient and controlled motion. Static structural and modal analyses were conducted to evaluate the mechanical behavior, while experimental testing validated the numerical predictions. The numerical analysis estimated a maximum displacement of 0.349 mm and a gripping force of 3.2 N, while experimental results measured 0.365 mm and 3.35 N, yielding deviations of 4.5
This paper aims at predicting the behavior of untethered magnetic microrobotic swarm (MMS), which also include emergent behaviors, from raw grayscale time-series image data. A fast dimensionality reduction algorithm for compressing image data set is proposed. Then based on the algorithm, an interpretable machine learning method which is based on Proper Orthogonal Decomposition (POD) and polynomial regression is proposed for feature extraction of compressed image data set and for further dimensionality reduction. The proposed method is reduced-order and purely data-driven not assuming any knowledge of the physics and/or interacting dynamics of MMS, which are extremely challenging to ascertain for systems of this nature and dimension. Finally, experimental results on several kinds of synthetic MMs show the effectiveness of the proposed method with less prediction error while using more dimensionality reduction than existing approaches in the literature.
This research presents the design, optimization, and validation of a soft robotic gripper intended as a multipurpose end effector for the IRB 1410 robot. The gripper is developed using soft silicone materials (Ecoflex 00–30) to ensure safe, adaptive handling of objects with varying shapes and fragility. Emphasizing modularity, the design allows the actuator to function independently or in combination with multiple configurations, increasing its versatility for industrial applications. Finite Element Analysis (FEA) was used to evaluate the mechanical response of the gripper under different pressures. At 200,000 Pa, the gripper achieved a deformation of 0.13934 m and maintained structural integrity, confirming its resilience under high strain. To optimize performance, the Taguchi method with L9 orthogonal arrays was applied. The optimal conditions 150,000 Pa pressure and 1.15 g/cm³ material density yielded deformation results closely matching experimental values. ANOVA revealed pressure as the dominant factor (99.9
Piezoelectric actuators are widely used in nano-positioning stage of atomic force microscopes (AFM). The nonlinear dynamics of these actuators adversely affect the AFM image quality unless they are compensated with a controller. We propose a feedforward controller design method which adjusts the scan waveforms with the aim of minimizing the hysteresis distortions in the lateral direction of motion. The data-driven design approach requires a pair of forward and backward stripes of images of the sample to detect the hysteresis mappings through solving a nonlinear optimization problem with a genetic algorithm. The parameters of the optimization are then used to shape the scan waveforms to compensate for the effects of hysteresis. The quick and straightforward design makes the proposed feedforward controller a good solution for lateral scanners in high-speed AFM where implementation of feedback control is often hindered by the physical constraints and latency of the system. We show that the design procedure can be successfully applied on AFM instruments regardless of the imaging mode, scan speed, or the sample under study.
The capability to precisely fabricate and manipulate small-scale liquid metal droplets is important for the development of emerging technologies in the fields of micro-robotics, printable electronics, biomedical engineering, and nanocharacterization. However, the reproducible fabrication of liquid metal droplets with diameters at the micro- and sub-micrometer scale at a precisely defined location remains a key challenge towards realizing these applications. In this study, we demonstrate that sub-micron diameter liquid metal droplets can be fabricated in a reproducible manner via the combination of an electromigration and focused ion beam (FIB)-induced sputtering process. Electromigration is used to generate droplets at specific locations, and FIB sputtering is used to control the final diameter of the droplets. Using Galinstan as a case study, the method is established by analyzing the actual sputtering yield of Galinstan processed with different FIB parameters. The reproducibility of fabricating liquid metal droplets with a radius of 10 m and 5 m is experimentally investigated, resulting in standard deviations of 0.168 m and 0.63 m, respectively. The evaluated fabrication method is therefore expected to be well suited for developing liquid metal-based robotic actuators, drug delivery devices, and contact angle measurement (CAM) techniques carried out inside the scanning electron microscope (SEM).
This paper presents a planar electromagnetic actuation-based nanopositioner with an integrated magnetic negative stiffness system. The proposed nanopositioner enables the achievement of a large range, high positioning speed, and multi-axis in-plane actuation without affecting the achievable actuation gain. The positioner comprises an array of conductive meanders suspended by conductive-compliant elements over a checkerboard of permanent magnets. The magnetic negative stiffness greatly reduces the stiffness along the actuation directions. Theoretical models are proposed for the estimation of magnetic force, magnetic stiffness and for the dynamic response of the positioner. The theoretical values are shown to agree with the finite element analysis results within 4.3
2-Photon Polymerization (2PP) 3D printing has allowed several interesting fabrication processes for microrobots. However, the use of 2PP for micromanipulators to create the largest workspace possible at small scale, and generate controllable, repeatable and multi-DoF movement capable of applying substantial forces is still an open question. Toward this goal, we investigate the behavior of 3D 100 m-scale tethered microrobots made with bi-material 2PP printing. Volumes of pNIPAM are used as actuators in an IP-S flexible mechanism, which takes the function of a structural skeleton of the microrobots. The force and displacement capabilities of pNIPAM actuators are studied experimentally and through Finite Element Modelling (FEM), revealing promising capacities in displacement and forces (measured contraction up to 30 N). The behavior of pNIPAM-actuated IP-S flexible mechanisms is investigated. The angular movement of pNIPAM-actuated IP-S rotational beam joint with varying dimensions was studied, and a max joint rotation of 23° was observed. Furthermore, a repeatable 80 μ m long motion was demonstrated on a 300 μ m long RR robot mechanism during 5 actuation cycles. Last, actuated 3D mechanisms are demonstrated with three 100 m grippers with two jaws oriented 45° around x, 45° around x and y, and three vertical jaws.
The development of flexure-based XYZ micro-positioning stages incorporating a novel type of flexure hinges with elliptical transverse cross-sections (ETC) is presented. In comparison to classical two-axis flexure hinges featuring rectangular transverse cross-sections (RTC), parametric studies of both the flexure hinges and the flexure stage were conducted, focusing on stress concentration, motion range, and output decoupling. The results demonstrate that the ETC-based XYZ flexure stage outperforms the RTC-based design in all three aspects. A prototype of the XYZ flexure stage utilizing ETC-type two-axis flexure hinges was developed and experimentally tested, achieving motion errors and parasitic motions of less than 5%. The ETC-type two-axis flexure hinges offer a novel approach for advancing spatial flexure stage design.
This paper deals with first investigations of a novel approach for conducting tensile tests on single plant fibres using direct microrobotic gripping. These fibres, typically around 20 micrometers in diameter, are gaining significant interest as renewable bio-sourced products. Usual methods for tensile testing generally involve mechanical clamping jaws or adhesive sample holders. This new approach intends to bring greater precision and repeatability of the test through the use of microgrippers, force sensors positioned in close proximity to the fibre and positioning control. A microrobotic experimental platform has been developed. Two different grippers are designed to address the important issue of clamping, the test boundary conditions. Experimental investigations are conducted on 20 tensile tests, validating the viability of the approach. Young’s modulus and stress at failure are identified and are in good correspondence with results available in the recent literature of flax fibres. The gripping force exerted by the gripper is a primary factor influencing the repeatability of the test. Therefore, a method is investigated to estimate this force. First experimental results enable to establish that these forces are in tens milliNewton-range forces. This establishes the interest for future works in the design of instrumented grippers able to control gripping forces during tensile tests in closed loop. Overall, this paper states the interest of a microrobotic approach for tensile tests fibres that opens to several future works including the automation, allowing a large number of fibres to be tested, especially fibres of short length, in order to reduce statistical biases.
Soft, magnetically actuated robots offer promising potential for medical applications due to their simple fabrication, controllability, cargo loading ability and flexibility. This research focuses on the design, modeling, and behavior of soft, millimeter-scale filamentous robots composed of Gelatin Methacrylate (GelMa) hydrogels and embedded with micromagnets for magnetic actuation. These robots are designed for navigation within the human urinary tract. The study investigates two distinct configurations: screw-like and fin-like robots, each responding differently to an external rotating magnetic field. The screw-like robots propel forward through synchronized helical motion, while the fin-like robots rely on interaction with surrounding surfaces for crawling motion. Experimental frequency response tests reveal that fin-like robots exhibit three times faster motion than screw-like robots in confined environments, reaching velocities of up to 18 mm/s. Additionally, the influence of micromagnet location inside the filaments on their propulsion dynamics is explored, highlighting the potential for optimized performance in medical applications requiring navigation through narrow channels, such as the ureter. Further optimization is proposed to enhance control and performance in more complex biological environments.
Classical mechanical joints limit the miniaturization level of mechanisms and robots. Soft joints provide a promising alternative as they can be highly miniaturized. Moreover, they can eliminate backlash and improve robotic precision. However, achieving high accuracy with soft joints requires precise mathematical models, often based on Finite Element Models (FEM). Although FEM offers high accuracy, it is too computationally intensive for high-speed, real-time applications. In this paper, we propose cubic soft joints as an alternative to spherical joints for miniaturized parallel robots. We demonstrate that these joints effectively approximate the behavior of spherical joints, enabling a simplified kinematic model that significantly reduces computational load without significantly compromising accuracy. This approximate model also simplifies the analysis of the robot’s singularity and workspace, as well as its optimization. Experimental results show minimal differences between the proposed model and more complex FEM models, yet the proposed approach is thousands of times faster, making high-speed, real-time control of such deformable mechanisms feasible. This advancement facilitates the development of complex, miniaturized robotic architectures with enhanced dexterity and manipulation capabilities.
