Robotic Capsule Endoscope Research Articles

A wirelessly powered expanding-extending robotic capsule endoscope for human intestine

Instruments for GI diagnostics are increasingly moving toward robotic capsule endoscopes because of their locomotion capabilities. This paper presents a wirelessly powered robotic capsule endoscope that can actively move in the small bowel exploiting the expanding–extending principle. After analyzing the demands of the locomotion, a novel radial motion mechanism with a large expanding/retracting radial ratio was designed, as was an axial motion mechanism with a compact structure. A control system with a special position detector to let the micro-motors avoiding stall state was developed to enhance the stability of the mechanism and reduce the robot’s power requirements. The wireless power system enabled the robot to inspect the full length of the intestinal tract. The assembled micro-robot was 14 mm in diameter and 45 mm in length. The maximum anchoring diameter was 32 mm, and the axial telescopic length was 9.5 mm. The test results proved the feasibility of the robot.

Fabrication and characterization of a magnetic micro-actuator based on deformable Fe-doped PDMS artificial cilium using 3D printing

This paper proposes the use of a 3D extrusion printer to fabricate artificial magnetic cilium. The cilia are fabricated using polydimethylsiloxane (PDMS) doped with iron particles so that they remain slender and flexible. They can be driven by a magnetic field to closely mimic the behaviour of biological cilia. Doping iron particles to the polymers has already been done; however, to the best of our knowledge, printing such active and soft magnetic structures has not. The existing methods for manufacturing magnetic polymeric structures are complex and difficult to use for the fabrication of micro-sized high-aspect-ratio cilia. The 3D printing technique we propose here is simple and inexpensive compared to previously suggested fabrication methods. In this study, free-standing magnetic PDMS cilia were fabricated in different sizes up to 5 mm in length and 1 mm in width. The stress-strain curves of the PDMS cilia were experimentally obtained to quantify the effect of the concentration of the iron particles on the modulus of elasticity of the cilia. The higher the iron concentration, the higher the modulus of elasticity. We have quantified the characteristics of the cilia made of 40% w/w iron particles in PDMS. A single cilium (5 × 1 × 0.0035 mm) can output up to 27 μN blocking force under a magnetic field of 160 mT. These cilia can be used as a mixer in lap-on-chip applications and as the anchoring and propulsion legs of endoscopic capsule robots operating within the gastrointestinal tract of humans. Analytical expressions estimating the blocking force are established and compared with the experimental results.

Intestinal biomechanics simulator for robotic capsule endoscope validation

This work describes the development and validation of a novel device which simulates important forces experienced by Robotic Capsule Endoscopes (RCE) in vivo in the small intestine. The purpose of the device is to expedite and lower the cost of RCE development. Currently, there is no accurate in vitro test method nor apparatus to validate new RCE designs; therefore, RCEs are tested in vivo at a cost of ∼$1400 per swine test. The authors have developed an in vitro RCE testing device which generates two peristaltic waves to accurately simulate the two biomechanical actions of the human small intestine that are most relevant to RCE locomotion: traction force and contact force. The device was successfully calibrated to match human physiological ranges for traction force (4–40 gf), contact force (80–500 gf) and peristaltic wave propagation speed (0.08–2 cm s−1) for a common RCE capsule geometry of 3.5 cm length and 1.5 cm diameter.

Soft material adhesion characterization for in vivo locomotion of robotic capsule endoscopes: Experimental and modeling results

The objective of this work is to validate an experimental method and nondimensional model for characterizing the normal adhesive response between a polyvinyl chloride based synthetic biological tissue substrate and a flat, cylindrical probe with a smooth polydimethylsiloxane (PDMS) surface. The adhesion response is a critical mobility design parameter of a Robotic Capsule Endoscope (RCE) using PDMS treads to provide mobility to travel through the gastrointestinal tract for diagnostic purposes. Three RCE design characteristics were chosen as input parameters for the normal adhesion testing: pre-load, dwell time and separation rate. These parameters relate to the RCE׳s cross sectional dimension, tread length, and tread speed, respectively. An inscribed central composite design (CCD) prescribed 34 different parameter configurations to be tested. The experimental adhesion response curves were nondimensionalized by the maximum stress and total displacement values for each test configuration and a mean nondimensional curve was defined with a maximum relative error of 5.6%. A mathematical model describing the adhesion behavior as a function of the maximum stress and total displacement was developed and verified. A nonlinear regression analysis was done on the maximum stress and total displacement parameters and equations were defined as a function of the RCE design parameters. The nondimensional adhesion model is able to predict the adhesion curve response of any test configuration with a mean R2 value of 0.995. Eight additional CCD studies were performed to obtain a qualitative understanding of the impact of tread contact area and synthetic material substrate stiffness on the adhesion response. These results suggest that the nondimensionalization technique for analyzing the adhesion data is sufficient for all values of probe radius and substrate stiffness within the bounds tested. This method can now be used for RCE tread design optimization given a set of environmental conditions for device operation.

Technical feasibility of patient-friendly screening and treatment of digestive disease by remote control robotic capsule endoscopes via the internet.

A few types of steerable capsule endoscopes have been proposed but disappointingly their systems were not applicable to common endoscopic treatment or pathological diagnosis. This study validates the possibility of treatment and biopsy by using an internet-linked (wireless control via the internet) robotic capsule endoscope (iRoboCap). iRoboCap consisted of three parts: an imaging unit, a movement control unit and a therapeutic tool unit. Two types of iRoboCaps were designed, one was a submarine type (iRoboCap-S) and the other was an amphibious type (iRoboCap-A). They were remotely and wirelessly steered by a portable tablet device using Bluetooth and via the internet. The success rates of biopsy or clipping were evaluated in a phantom. Although the two prototypes have various problems that need improving, we hope that our robotic and wireless innovations have opened the door to new endoscopic procedures and will pioneer various new applications in medicine.

An Automated Intestinal Biomechanics Simulator for Expediting Robotic Capsule Endoscope Development1

An Automated Intestinal Biomechanics Simulator for Expediting Robotic Capsule Endoscope Development1

Application of wireless power transmission systems in wireless capsule endoscopy: an overview.

Wireless capsule endoscopy (WCE) is a promising technology for direct diagnosis of the entire small bowel to detect lethal diseases, including cancer and obscure gastrointestinal bleeding (OGIB). To improve the quality of diagnosis, some vital specifications of WCE such as image resolution, frame rate and working time need to be improved. Additionally, future multi-functioning robotic capsule endoscopy (RCE) units may utilize advanced features such as active system control over capsule motion, drug delivery systems, semi-surgical tools and biopsy. However, the inclusion of the above advanced features demands additional power that make conventional power source methods impractical. In this regards, wireless power transmission (WPT) system has received attention among researchers to overcome this problem. Systematic reviews on techniques of using WPT for WCE are limited, especially when involving the recent technological advancements. This paper aims to fill that gap by providing a systematic review with emphasis on the aspects related to the amount of transmitted power, the power transmission efficiency, the system stability and patient safety. It is noted that, thus far the development of WPT system for this WCE application is still in initial stage and there is room for improvements, especially involving system efficiency, stability, and the patient safety aspects.

Sensor for Measuring the Contact Force From Human Myenteric Contractions for In Vivo Robotic Capsule Endoscope Mobility

Sensor for Measuring the Contact Force From Human Myenteric Contractions for In Vivo Robotic Capsule Endoscope Mobility

Experimental research on anchoring force in intestine for the motion of capsule robot

Multiple research groups are currently attempting to develop less-invasive robotic capsule endoscopes (RCEs) with better outcomes for enteroscopic procedures. Understanding the biomechanical response of the bowel to RCE is crucial for optimizing the design of these devices. For this reason, this study aims to develop an analytical model to predict the anchoring force of the model when travelling through the intestine. Previous work has developed, characterized and tested the frictional characteristics of the intestine with microgroove structures that had different surface contours. This work tested basic anchoring force characteristics with custom-built testers and clamping mechanism dummies to analyse the robot clamping movement (which is vital to improving movement efficiency). Balloon-shaped and leg-based clamping mechanisms were developed, which were found to have variable anchoring forces from 0.01 N to 1.2 N. After analysing the experimental results it was found that: (a) robot weight does not play a major role in anchoring force; (b) an increase in anchoring force corresponded to an increase in diameter of the clamping mechanism; and (c) textured contact surfaces effectively increased friction. These results could be explained by the biomechanical response of the intestine, friction and mucoadhesion characteristics of the small intestine material. With these factors considered, a model was developed for determining anchoring force in the small intestine.

Navigation of a robotic capsule endoscope with a novel ultrasound tracking system

Capsule endoscopes used for diagnosis in the gastro intestinal tract have gained much popularity in recent years due to the minimized patient discomfort and available operating range. New therapeutic applications of these devices are surgical interventions or medication at specific locations. So far capsule endoscopic devices are passively propelled prohibiting these new approaches. To overcome this issue we presented a Magnet Drive Unit (MDU) for external actuation for robotic capsule devices in our previous work. While MDU is used for manipulation of a capsule-robot, there has not been any information of the current location of the robot within the patient. Therefore, we propose a novel ultrasound based tracking system for the capsule-robot and endoscopic devices in this manuscript. The tracking system consists of a Cartesian robot actuating a transcutaneous sonographic probe in two degrees of freedom. While the capsule-robot is propelled by MDU, our tracking system generates sonographic images through the back of the patient showing the current location of the capsule. The results of our experiments unveil that our concept is feasible and can be used to navigate a robotic capsule device inside the human body.

A tribological investigation of the small bowel lumen surface

Robotic capsule endoscopy (RCE), where a robotically controlled capsule endoscope is used to navigate the gastrointestinal tract, is a developing technology currently hindered by mobility challenges within the small bowel. This research seeks to engage the frictional characterization of the small bowel with a formally designed experiment which samples the variability within the porcine animal population while parameters such as engineering material, contact area and bowel region were varied. Friction force measurements were collected within an environmental chamber which closely simulates in vivo conditions. The results indicate that micro-patterned polydimethylsiloxane (PDMS) yields a statistically significantly higher coefficient of friction (COF) than stainless steel or polycarbonate. The effects of contact area and bowel region vary across the porcine animal population. The COF under these conditions ranged from 0.0004 to 0.018.

Small intestine mucosal adhesivity to in vivo capsule robot materials

Multiple research groups are investigating the feasibility of miniature, swallowable, in vivo, untethered robots that are capable of traversing the small intestine for the purpose of acquiring biometrics and performing simple surgical procedures. A mathematical model of the intraluminal environment will speed the development of these so-called Robotic Capsule Endoscopes (RCEs), and to this end, the authors, in previous work, initiated a comprehensive program for characterizing both the active and passive forces exerted by the small intestine on an RCE-sized solid bolus. In this work, forces due to adhesivity between RCE materials and the mucosa are investigated. The experimental factors are adhesive modality (peel and tack), material (polycarbonate, micropatterned polydimethylsiloxane, stainless steel, and mucosa), and bowel region (proximal, middle, and distal). The mucosa is excised from a fasting pig, stored in lactated ringer's solution at 3°C, and then tested at room temperature within 43h of excision. The results show the mean tack strength of the mucosa to engineering materials was 0.198±0.070mJcm−2. The mean peel strength was 0.055±0.016mJcm−2. This study marks the first time, to the authors' knowledge, that adhesivity between small intestinal mucosa and RCE engineering materials has been measured. The adhesivity values acquired from this study will provide a valuable input into analytical and numerical models of the gastrointestinal tract, specifically models that account for the interfacial properties of the tissue.

Characterization and Experimental Results of a Novel Sensor for Measuring the Contact Force From Myenteric Contractions

The intraluminal pressures and traction forces associated with the migrating motor complex are well understood; however, the contact forces directly exerted by the bowel wall on a solid, or near solid, bolus have not previously been measured. Quantifying contact forces is an important component to understanding the net force experienced by an in vivo robotic capsule endoscope. In this paper, we develop a novel sensor, the migrating motor complex force sensor (MFS), for measuring the contact force generated by the contracting myenteron of the small intestine. The MFS consists of a perfused manometer connected to four torus-shaped balloons custom formed of natural latex rubber and embedded with temperature and pressure sensors. Force exerted on the balloon causes sensor pressure change. In vivo, the MFS measures the magnitude and axial location of contact pressure exerted by the myenteron. The device is tested in vivo in a live porcine model on the middle small bowel. The mean total force per centimeter of axial length of intestine that occurred over a 16-min interval in vivo was 1.04 N·cm (-1) in the middle region of the small intestine; the measured force is in the range of theoretical values.

The Design and Characterization of a Testing Platform for Quantitative Evaluation of Tread Performance on Multiple Biological Substrates

In this study, an experimental platform is developed to quantitatively measure the performance of robotic wheel treads in a dynamic environment. The platform imposes a dynamic driving condition for a single robot wheel, where the wheel is rotated on a translating substrate, thereby inducing slip. The normal force of the wheel can be adjusted mechanically, while the rotational velocity of the wheel and the translational velocity of the substrate can be controlled using an open-loop control system. Wheel slip and translational speed can be varied autonomously while wheel traction force is measured using a load cell. The testing platform is characterized by testing one micropatterned polydimethylsiloxane (PDMS) tread on three substrates (dry synthetic tissue, hydrated synthetic tissue, and excised porcine small bowel tissue), at three normal forces (0.10, 0.20, and 0.30 N), 13 slip ratios (-0.30 to 0.30 in increments of 0.05), and three translational speeds (2, 3, and 6 mm/s). Additionally, two wheels (micropatterned and smooth PDMS) are tested on beef liver at the same three normal forces and translational speeds for a tread comparison. An analysis of variance revealed that the platform can detect statistically significant differences between means when observing normal forces, translational speeds, slip ratios, treads, and substrates. The variance due to within (platform error, P = 1) and between trials (human error, P = 0.152) is minimal when compared to the normal force (P = 0.036), translational speed ( P = 0.059), slip ratio (P = 0), tread (P = 0.004), and substrate variances ( P = 0). In conclusion, this precision testing platform can be used to determine wheel tread performance differences on the three substrates and for each of the studied parameters. Future use of the platform could lead to an optimized micropattern-based mobility system, under given operating conditions, for implementation on a robotic capsule endoscope.

Surgical evaluation of a novel tethered robotic capsule endoscope using micro-patterned treads

The state-of-the-art technology for gastrointestinal (GI) tract exploration is a capsule endoscope (CE). Capsule endoscopes are pill-sized devices that provide visual feedback of the GI tract as they move passively through the patient. These passive devices could benefit from a mobility system enabling maneuverability and controllability. Potential benefits of a tethered robotic capsule endoscope (tRCE) include faster travel speeds, reaction force generation for biopsy, and decreased capsule retention. In this work, a tethered CE is developed with an active locomotion system for mobility within a collapsed lumen. Micro-patterned polydimethylsiloxane (PDMS) treads are implemented onto a custom capsule housing as a mobility method. The tRCE housing contains a direct current (DC) motor and gear train to drive the treads, a video camera for visual feedback, and two light sources (infrared and visible) for illumination. The device was placed within the insufflated abdomen of a live anesthetized pig to evaluate mobility performance on a planar tissue surface, as well as within the cecum to evaluate mobility performance in a collapsed lumen. The tRCE was capable of forward and reverse mobility for both planar and collapsed lumen tissue environments. Also, using an onboard visual system, the tRCE was capable of demonstrating visual feedback within an insufflated, anesthetized porcine abdomen. Proof-of-concept in vivo tRCE mobility using micro-patterned PDMS treads was shown. This suggests that a similar method could be implemented in future smaller, faster, and untethered RCEs.

Measurements of the contact force from myenteric contractions on a solid bolus.

The development of robotic capsule endoscopes (RCEs) is one avenue presently investigated by multiple research groups to minimize invasiveness and enhance outcomes of enteroscopic procedures. Understanding the biomechanical response of the small bowel to RCEs is needed for design optimization of these devices. In previous work, the authors developed, characterized, and tested the migrating motor complex force sensor (MFS), a novel sensor for quantifying the contact forces per unit of axial length exerted by the myenteron on a solid bolus. This work is a continuation, in which the MFS is used to quantify the contractile strength in the small intestine proximal, middle, and distal regions of five live porcine models. The MFSs are surgically implanted in a generally anesthetized animal, and force data from 5min of dwell time are analyzed. The mean myenteric contact force from all porcine models and locations within the bowel is 1.9±1.0Ncm(-1). Examining the results based on the small bowel region shows a statistically significant strengthening trend in the contractile force from proximal to middle to distal with mean forces of 1.2±0.5, 1.9±0.9, and 2.3±1.0Ncm(-1), respectively (mean ± one standard deviation). Quantification of the contact force against a solid bolus provides developers of RCEs with a valuable, experimentally derived parameter of the intraluminal environment.

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.

An endoscopic capsule robot: a meso-scale engineering case study

A number of unique challenges arise in fabricating and assembling complex mechanisms at the meso-scale (hundreds of microns to centimetres). In general, for a complex multi-part mechanism at this length scale, no single machining technique can produce all the necessary parts—or often even a single individual part. Towards developing a comprehensive set of ‘best practices’ for combining multiple precision micromachining operations at the meso-scale, we present a case study on fabricating and assembling an endoscopic capsule robot. Existing passive imaging capsules have proven exceptionally useful in the diagnosis of the gastrointestinal tract, and robotic capsules promise to enhance their diagnostic capabilities and enable non-invasive treatment delivery. In this case study, we describe the fabrication of a robotic capsule (2.6 cm3 in volume) containing a complex mechanism consisting of 72 components, each of which requires a variety of meso- or even micro-scale features. We describe the manufacturing processes used to produce these components and features (combinations of high precision, multiply refixtured computer numerical control processes, sink and wire electro discharge machining, laser cutting, etc). These results contribute to the emerging framework of best practices in meso-scale design and manufacture, illustrating ways to effectively combine several processes to produce a complex meso-scale device.

Experimental investigation of frictional and viscoelastic properties of intestine for microendoscope application

The information on the frictional resistance of a self-propelled robotic capsule endoscope moving inside the body is very important for the design and the performance enhancement of such parameters of the capsule endoscope as power consumption, motion control and positioning accuracy. Based on this motivation, the ultimate goal of this research was to develop an analytical model that can predict the frictional resistance of the capsule endoscope moving inside the living body. In this work, experimental investigations of the fundamental frictional characteristics and the viscoelastic behaviors of the small intestine were performed by using custom-built testers and various capsule dummies. The small intestine of a pig was used for the experiments. Experimental results showed that the average frictional force was 10–50 mN and higher moving speed of the capsule dummy resulted in larger frictional resistance of the capsule. In addition, the friction coefficient did not change significantly with respect to the apparent area of contact between the capsule dummy and the intestine, and also the friction coefficients decreased with an increase in the normal load and varied from 0.08 to 0.2. Such frictional behaviors could be explained by the lubrication characteristics of the intestine surface and typical viscoelastic characteristics of the small intestine material. Also, based on the experimental results, a viscoelasticity model for the stress relaxation of the small intestine could be derived.

EFFICIENT MAGNETIC LOCALIZATION AND ORIENTATION TECHNIQUE FOR CAPSULE ENDOSCOPY

To build a new wireless robotic capsule endoscope with external guidance for controllable and interactive GI tract examination, a sensing system is needed for tracking 3D location and 2D orientation of the capsule endoscope movement. An appropriate sensing method is to enclose a small permanent magnet in the capsule. The intensities of the magnetic field produced by the magnet in different spatial points can be measured by the magnetic sensors outside the patient's body. With the sensing data of magnetic sensor array, the 3D location and 2D orientation of the capsule can be calculated. Higher calculation accuracy can be obtained if more sensors and optimal algorithm are applied. In this paper, different nonlinear optimization algorithms were evaluated to solve the magnet's 5D parameters, e.g. Powell's, Downhill Simplex, DIRECT, Multilevel Coordinate Search, and Levenberg Marquardt method. We have found that Levenberg-Marquardt method provides satisfactory calculation accuracy and faster speed. Simulations were done for investigating the de-noise ability of this algorithm based on different sensor arrays. Also the real experiment shows that the results are satisfactory with high accuracy (average localization error is 5.6 mm).