Marco Quirini

A New Mechanism for Mesoscale Legged Locomotion in Compliant Tubular Environments

We present design and experimental performance results for a novel mechanism for robotic legged locomotion at the mesoscale (from hundreds of microns to tens of centimeters). The new mechanism is compact and strikes a balance between conflicting design objectives, exhibiting high foot forces and low power consumption. It enables a small robot to traverse a compliant, slippery, tubular environment, even while climbing against gravity. This mechanism is useful for many mesoscale locomotion tasks, including endoscopic capsule robot locomotion in the gastrointestinal tract. It has enabled fabrication of the first legged endoscopic capsule robot whose mechanical components match the dimensions of commercial pill cameras (11 mm diameter by 25 mm long). A novel slot-follower mechanism driven via lead screw enables the mechanical components of the capsule robot to be as small while simultaneously generating 0.63 N average propulsive force at each leg tip. In this paper, we describe kinematic and static analyses of the lead screw and slot-follower mechanisms, optimization of design parameters, and experimental design and tuning of a gait suitable for locomotion. A series of ex vivo experiments demonstrate capsule performance and ability to traverse the intestine in a manner suitable for inspection of the colon in a time period equivalent to standard colonoscopy.

Design and Fabrication of a Motor Legged Capsule for the Active Exploration of the Gastrointestinal Tract

This paper describes a novel solution for the active locomotion of a miniaturized endoscopic capsule in the gastrointestinal (GI) tract. In particular, the authors present the design, development, and testing of a legged locomotion system embedded in a capsule (with a volume of about 4-5 cm3) and actuated by a brushless minimotor. The actuation mechanism and transmission mechanism are described in detail in order to highlight the compactness of the overall design. This device is provided with four superelastic legs, allowing large stroke advancement in the GI tract, and a CMOS frontal camera, for diagnostic purposes. A dedicated electronic board for controlling the opening angle of the legs and adjusting their speed has been developed. In order to investigate the motion ability of the device, a set of experiments has been carried out. Four different types of superelastic legs have been designed and tested with the objective to identify the best leg configuration for capsule locomotion. Experimental results demonstrate that the device can travel in the digestive tract with a typical speed ranging between 10 and 40 mm/min.

Design of a Pill-Sized 12-legged Endoscopic Capsule Robot

In this paper we present the design of a swallowable (11mm diameter by 25mm long), 12-legged endoscopic capsule for locomotion in the lower gastro intestinal tract (large bowel). A novel slot-follower mechanism driven via lead-screw allows the capsule to be as small as current commercial pill-cameras, while simultaneously generating 2/3 N of force at each leg tip. Kinematic and static analyses of the lead screw and slot-follower mechanisms allow optimization of design parameters so that the capsule satisfies experimental and clinical design requirements for legged locomotion in the GI tract.

Microrobotics for future gastrointestinal endoscopy

The impulse given by robotic technologies and imaging techniques to the development of a new way to conceive and perform surgery is clearly visible. Nowadays, minimally invasive surgical (MIS) procedures are often performed with the assistance of robots, such as the Da Vinci master‐slave system, the AESOP robot with voice control, etc. In addition, mechatronic technologies are becoming the elective technologies for designing advanced hand‐held surgical tools. The introduction of robotic technologies in endoscopy has been slower than in MIS, since the development of miniaturized robotic components for entering the small orifices of the human body is difficult. On the other hand, the large contribution that robotic technologies could bring to endoluminal techniques has been evident since the first development of instrumented catheters. In the 1990s, there was an increasing activity in the application of robotic technologies to improve endoscopic procedures in the gastrointestinal tract. The objective of robotic colonoscopy and gastroscopy was to obtain more effective diagnoses in terms of reduced pain for the patients, and to make uniform the diagnostic procedures, which too often depended on the manual abilities of the endoscopist. Currently, the availability of more reliable robotic technologies for miniaturization of size and integration of functions has allowed to conceive and develop robotic pills for the early screening of the digestive tract, with dramatic potential advantages for patients, endoscopists, and healthcare system.

A Novel SMA-Based Actuator for a Legged Endoscopic Capsule

This paper describes the design, modelling and fabrication of a shape memory alloy micro-actuation concept for application in an endoscopic capsule. The constraints of the actuators are discussed based on the planned integration in a swallowable capsule and a preliminary concept of a legged system with shape memory alloy actuation is presented and tested. Based on the preliminary results, a modelling of the system is given in order to optimize the actuator design in terms on length, diameter, angle and force. Thus, a new high performance prototype is developed and characterized, thus verifying the theoretical model

An Approach to Capsular Endoscopy with Active Motion

This paper describes a novel approach to capsular endoscopy that takes advantage of active legged locomotion in the gastro intestinal tract. The basic and essential functions that such a microdevice must possess are listed and discussed in details, as well as the specific features required in the different districts of the digestive path. Active legged locomotion was selected to achieve the adequate degree of flexibility and accuracy during the capsule journey. In addition, on-board locomotion mechanisms would allow to avoid bulky external driving systems that are typical of externally actuated devices. Two different prototypes, having 4 and 8 legs respectively, are presented, evaluated and tested. In particular, the 8-leg solution achieved a speed of 6 cm/min during in vitro tests. Moreover, it demonstrated capabilities of backward locomotion, vertical locomotion and locomotion around acute bends.

Towards active capsular endoscopy: preliminary results on a legged platform

This paper illustrates the problem of active locomotion in the gastrointestinal tract for endoscopic capsules. Authors analyze the problem of locomotion in unstructured, flexible and tubular environments and explain the reasons leading to the selection of a legged system. They present a theoretical simulation of legged capsule locomotion, which is used to define the optimal parameters for capsule design and gait selection. Finally, a legged capsule - about 3 cm3in volume - is presented; it consists of 4 back legs whose actuation is achieved thanks to a miniaturized DC brushless motor. In vitro tests demonstrate good performance in terms of achievable speed (92 mm/min)

Superelastic leg design optimization for an endoscopic capsule with active locomotion

Nowadays Nitinol structures are accepted and highly exploited in the medical field. Therefore, studying the mechanical properties of this material—which is not trivial by considering the thermal behaviour of the alloy—is very important in order to get quantitative data for a reliable design of novel Nitinol components. In particular, this study focuses on the design optimization of superelastic Nitinol legs to be integrated into an endoscopic capsule for biomedical applications. The leg is provided with an elastic knee that adds a passive degree of freedom to the structure; this solution allows us to achieve a good locomotion adaptability in the unstructured environment of the gastrointestinal tract, characterized by different diameters. First, the mechanical behaviour of Nitinol was analysed. Tensile tests were carried on in order to extract the peculiar stress–strain curve of the material. The hysteretic behaviour was observed through 100 loading–unloading cycles. The acquired data were used to model the leg design by finite element methods (FEM) and to estimate the stress–strain internal state during the operative work. These data were used to optimize the leg, which was finally fabricated and tested, demonstrating an improvement of five times regarding the number of cycles before leg failure.

Development of a legged capsule for the gastrointestinal tract: an experimental set-up

The experimental study reported in this paper illustrates the development of a legged locomotion system for autonomous medical microrobots with the final goal to perform gastrointestinal (GI) diagnosis by minimally invasive endoscopy. An active teleoperated diagnostic capsule should be able to adapt its gait to changing gut diameters and vary its patterns to turn, rotate or stop based on the encountered pathologies. Therefore, in order to obtain propulsion in the GI tract, locomotion effectiveness, adaptability and dexterity are required. A biomechanical integrative approach has been followed, based on the investigation of biological legged locomotion models, with the aim to derive design rules for a legged artificial system. Because of the locomotion parameters which are critical for obtaining an effective locomotion are a lot and they are often difficult to be modelled and simulated, an experimental set-up has been developed in order to accomplish the problem analysis before designing the final endoscopic wireless capsule. An hexapod device with a sprawled insect-like posture has been developed. The device is provided with six superelastic legs, which are actuated by push-pull cables moved by traditional DC servomotors. Preliminary tests on porcine bowel and on latex GI simulators have been performed on a dedicated and sensorized design of a future test-bench, thus allowing to derive important guidelines for the wireless capsule development and for implementing the best gait