Plant cells expand and elongate. Their cumulative actuation defines organ morphing. Inspired by this modular transformability, this study proposes a modular concept for growing robots that will be able to grow by adding at their tip Transformable Modules (TMs). We provide a two-module implementation to evaluate the concept viability. We designed and characterized Shape-Retention Bellows (SRBs) that constitute the TM and are used to maintain the shape once the extension force is relaxed. We demonstrate module radial expansion and axial elongation in a straight and bent configuration (up to ~4°). This is the first concept of growing robots to enact the robot's modularity and transformability for future deployment in distributed growing systems capable of acting in various scenarios.

Microrobots (MRs) have attracted growing interest for their potentialities in diagnosis and noninvasive intervention in hard-to-reach body areas. The safe operation of biomedical MRs requires fine control capabilities, which strongly depend on precise and robust feedback about their position over time. Ultrasound acoustic phase analysis (US-APA) may allow for a reliable feedback strategy for MR imaging and tracking in tissue. In this article, we combine task-specific magnetic actuation and related US-APA motion tracking to achieve closed-loop navigation of a magnetic MR, rolling on the boundary of a lumen in a tissue-mimicking phantom. A C-arm system attached to a robotic platform is used to precisely position the magnetic actuation source and US-APA detection unit within the workspace, thus enabling MR visual-servoing. In the first place, the proposed approach allows to perform supervised localization of the MR without anya-prioriknowledge of its position. After localization, a robust real-time tracking enables closed-loop MR teleoperation in the phantom lumina over a travel distance of 80 mm (145 body lengths), both in static and counter flow, thus achieving an average position tracking error of 368 micron (0.67 body lengths). For the first time, our results validate US-APA as a reliable feedback strategy for visual-servoing control of MRs in simulated in-body environment.

Untethered magnetic microrobots hold the potential to penetrate hard-to-reach areas of the human body and to perform therapy in a controlled way. In the past decade, impressive advancements have been made in this field but the clinical adoption of magnetoresponsive microrobots is still hampered by safety issues. A tool appointed for magnetic microrobots retrieval within body fluids could enable a real paradigm change, fostering their clinical translation.By starting from the general problem to retrieve magnetic microrobots injected into the bloodstream, the authors introduce a magnetic capture model that allows to design retrieval tools for magnetic cores of different diameters (down to 10 nm) and in different environmental conditions (fluid speed up to 7 cms-1). The model robustness is demonstrated by the design and testing of a retrieval catheter. In its optimal configuration, the catheter includes 27 magnets and fits a 12 F catheter. The model provides a good prediction of capture efficiency for 250 nm magnetic particles (experimental data: 77.6%, model prediction: 65%) and a very good prediction for 500 nm particles (experimental data: 93.6%, model prediction: 94%). The results support the proposed model-based design approach, which can be extended to retrieve other magnetoresponsive agents from body compartments.

While intraoperative imaging is commonly used to guide surgical interventions, automatic robotic support for image-guided navigation has not yet been established in clinical routine. In this paper, we propose a novel visual servoing framework that combines, for the first time, full image-based 3D ultrasound registration with a real-time servo-control scheme. Paired with multi-modal fusion to a pre-interventional plan such as an annotated needle insertion path, it thus allows tracking a target anatomy, continuously updating the plan as the target moves, and keeping a needle guide aligned for accurate manual insertion. The presented system includes a motorized 3D ultrasound transducer mounted on a force-controlled robot and a GPU-based image processing toolkit. The tracking accuracy of our framework is validated on a geometric agar/gelatin phantom using a second robot, achieving positioning errors of on average 0.42-0.44 mm. With compounding and registration runtimes of up to total around 550 ms, real-time performance comes into reach. We also present initial results on a spine phantom, demonstrating the feasibility of our system for lumbar spine injections.

Wireless capsule endoscopy recently demonstrated its potential as leading technology for gastrointestinal tract examinations. Many research groups are focusing their efforts on the design of active locomotion methods to allow a complete maneuverability of the device along the gastrointestinal tract. A promising approach for locomotion is represented by master-slave magnetic coupling; however the typical large gradients of magnetic forces make device controllability very hard with important safety concerns: in this framework magnetic capsule localization and interaction force control become extremely relevant. In the present work, a preliminary on-line localization has been implemented obtaining a position feedback closed loop control of a magnetic driven capsule endoscope. Furthermore, interaction forces with the environment have been evaluated by exploiting a dedicated setup for magnetic dragging. Distributed charges-current and dipole-dipole magnetic models applied to capsule endoscopy have been investigated and results have been compared with experimentally measured magnetic forces. Advantages and limitations of employed models have been evaluated and their usability for Real-Time force calculation has been discussed.

Exploitation of miniature robots and microrobots for endovascular therapeutics is a promising approach; besides chemical strategies (typically systemic), topical mechanical approaches exist for obstruction removal, which however produce harmful debris for blood circulation. Magnetic particles (MPs) are also studied for blood clot targeting. We investigated magnetic dragging of clots/debris by means of both electrostatic and antibody binding. We successfully produced magnetotactic blood clots in vitro and experimentally showed that they can be effectively dragged within a fluidic channel. We also exploited a magnetic force model in order to quantitatively analyze the experimental results, up to obtaining an estimate of the relative efficiency between electrostatic and antibody binding. Our study takes a first step towards more realistic in vivo investigations, in view of integration into microrobotic approaches to vascular obstructions removal.

In this paper the development of a bio-robotic platform is described. The robot design exploits biomechanical and neuroscientific knowledge on the lamprey, an eel-like swimmer well studied and characterized thanks to the reduced complexity of its anatomy. The robot is untethered, has a compliant body, muscle-like high efficiency actuators, proprioceptive sensors to detect stretch and stereoscopic vision. Experiments on the platform are reported, including robust and autonomous goal-directed swimming. Extensive experiments have been possible thanks to very high energy efficiency (around five hour continuous operating) the platform is ready to be used as investigation tool for high level motor tasks.

We present the design and development of novel suction cups inspired by the octopus suckers. Octopuses use suckers for remarkable tasks and they are capable to obtain a good reversible wet adhesion on different substrates. We investigated the suckers morphology that allow octopus to attach them to different wet surfaces to obtain the benchmarks for new suction cups showing similar performances. The investigation was performed by using non-invasive techniques (i.e. ultrasonography and magnetic resonance imaging). We acquired images of contiguous sections of octopus suckers, which were used to make a 3D reconstruction aimed to obtain a CAD model perfectly equivalent to the octopus sucker in terms of sizes and anatomical proportion. The 3D information was used to develop the first passive prototypes of the artificial suction cups made in silicone. Then, in accordance with Kier and Smith's octopus adhesion model, we put in tension the water volume in the interior chamber of the artificial suction cup to obtain suction. The characterization of the passive sucker was addressed by measuring both the differential pressure between external and internal water volume of suction cup (~ 105) and the pull-off force applied to detach the substrates from the suction cup (~ 8N).

A novel mechanism for actuating a miniature swimming robot is described, modeled, and experimentally validated. Underwater propulsion is obtained through the interaction of mobile internal permanent magnets that move a number of polymeric flaps arranged around the body of the robot. Due to the flexibility of the proposed swimming mechanism, a different range of performances can be obtained by varying the design features. A simple multiphysics dynamic model was developed in order to predict basic behavior in fluids for different structural parameters of the robot. In order to experimentally verify the proposed mechanism and to validate the model, a prototype of the swimming robot was fabricated. The device is 35 mm in length and 18 mm in width and thickness, and the forward motion is provided by four flaps with an active length of 20 mm. The model was able to correctly predict flap dynamics, thrust, and energy expenditure for magnetic dragging within a spindle-frequency range going from 2 to 5 Hz. Additionally, the model was used to infer robot-thrust variation related to different spindle frequencies and a 25% increase in flap active length. Concerning swimming performance, the proposed technical implementation of the concept was able to achieve 37 mm/s with 4.9% magnetic mechanism efficiency.

Polymeric ultra-thin films, also called nanosheets, show peculiar properties in terms of thickness, flexibility and chemical structure. For these reasons, they were proposed as nanoplasters for localized drug release or as a new solution for closing endoluminal surgical wounds. This paper presents the fabrication and characterization of free-standing nanosheets loaded with iron oxide nanoparticles, which can be manipulated in liquid environment by means of magnetic fields. A theoretical model of magnetic manipulation of the nanosheet is proposed and validated by dragging the film with a permanent magnet mounted on an industrial robotic arm. Controlling the magnetic sheet in liquid environment represents a first step towards the application of these nanostructures as free-standing carriers to be released and magnetically controlled in endoluminal surgery or as plasters with nanometric thickness to be delivered in situ on surgical incisions. Furthermore, these magnetic nanofilms can be adapted and used as micro and nanocomponents for the design of a novel generation of magnetic actuated polymeric microrobots.