Macro-Scale Tread Patterns for Traction in the Intestine

GOAL

Tread patterns are widely used to increase traction on different substrates, with the tread scale, geometry and material being tailored to the application. This work explores the efficacy of using macro-scale tread patterns for a medical application involving a colon substrate - renowned for its low friction characteristics.

METHODS

Current literature was first summarized before an experimental approach was used, based on a custom test rig with ex vivo porcine colon, to assess different macro-scale tread patterns. Performance was based on increasing traction while avoiding significant trauma. Repeated testing (n = 16) was used to obtain robust results.

RESULTS

A macro-scale tread pattern can increase the traction coefficient significantly, with a static traction coefficient of 0.74 ± 0.22 and a dynamic traction coefficient of 0.35 ± 0.04 compared to a smooth (on the macro-scale) Control (0.132 ± 0.055 and 0.054 ± 0.015, respectively). Decreasing the scale and spacing between the tread features reduced apparent trauma but also reduced the traction coefficient.

CONCLUSION

Significant traction can be achieved on colon tissue using a macro-scale tread but a compromise between traction (large feature sizes) and trauma (small feature sizes) may have to be made.

SIGNIFICANCE

This work provides greater insight into the complex frictional mechanisms of the intestine and gives suggestions for developing functional tread surfaces for a wide range of clinical applications.

Development of a Capsule Robot for Exploring the Colon

A tether-less inchworm-like capsule robot (ILCR) is promising to enable a non-invasive exploration of the colon, while existing ILCRs show barely satisfactory movement performance because the colon environment is nonstructural. In this current study, we develop an enhanced ILCR based on a design rule of maximizing the achievable periodic stroke and minimizing the body length, with the aim of improving movement performance. By designing an axial compact expanding mechanism (EM), employing a novel linear mechanism (LM), and integrating a hollow-cylinder-like power source based on wireless power transmission (WPT), the enhanced ILCR achieves a periodic stroke of 38 mm within a small body length of 33 mm. Our experiments show that the EM and LM can work reliably in an ex-vivo colon with a lot of intestinal mucus, and the power source can safely supply a stable working voltage of 3.3 V even in the worst case. Being wirelessly controlled and powered, the enhanced ILCR shows satisfactory movement performance, with velocities of 15.8 cm/min, 12.1 cm/min, and 7.4 cm/min in a transparent tube, a tiled colon, and a suspended colon, respectively, promising to accomplish an exploration for the 1.5-m long colon within 30 min.

Locomotion enhancement of an inchworm-like capsule robot using long contact devices

BACKGROUND

The inchworm-like capsule robot (CR), which consists of two anchoring mechanisms (AMs) and an extensor, is a promising device for exploring the human intestine. However, the slippery intestinal lumen can cause anchoring slippage and the visco-elastic intestine and mesentery can cause stroke loss, which both lower its locomotion performance.

METHODS

This paper proposes a method for locomotion enhancement by optimizing the lengths of the contact devices that are installed at the tips of the AM.

RESULTS

Theoretical analysis showed that a longer contact device was more beneficial to avoid slippage and reduce stroke loss, hence enhancing locomotion, which was then verified by ex vivo experiments. The 34.5 mm long contact devices enabled a locomotion efficiency of 54%, while it was only 21% when employing 5 mm long contact devices.

CONCLUSIONS

The inchworm-like CR using long contact devices can enable a more efficient inspection of the intestine. Copyright © 2016 John Wiley & Sons, Ltd.

Fabrication and evaluation of polymer-based esophageal stents for benign esophagus stricture insertion

In benign esophageal strictures, polymeric lines and membranes were chosen to knit an esophageal stent for relieving esophageal lesions caused by esophageal stenosis and obstruction.

The friction of sliding wet textured surfaces: the Bruggeman effective medium approach revisited

The mean field fluid dynamics and the friction occurring in the wet sliding contact between inhomogeneous surfaces, characterized by a deterministically repeated pattern of microdefects, are modelled within the Bruggeman effective medium theory. By comparing with the results of an accurate numerical homogenization of the flow equations, and with asymptotic solutions, we discuss the validity of the mean field model and its limitations in relation to the occurrence of clustering and interference effects. Finally, an analytical upgrade to the Bruggeman approach, allowing for inclusion of the clustering effect, is presented and discussed.

Design, analysis, and testing of a motor-driven capsule robot based on a sliding clamper

We propose a motor-driven capsule robot based on a sliding clamper (MCRSC), a device to explore the partially collapsed and winding intestinal tract. The MCRSC is powered by wireless power transmission based on near-field inductive coupling. It comprises a novel locomotion unit, a camera, and a three-dimensional receiving coil, all installed at both ends of the locomotion unit. The novel locomotion unit comprises a linear motion mechanism and a sliding clamper. The former adopts a pair of lead-screw and nut to obtain linear motion, whereas the latter anchors the MCRSC to a specific point of the intestinal tract by expanding its arc-shaped legs. The MCRSC is capable of two-way locomotion, which is activated by alternately executing linear motion and anchoring action. Ex vivo experiments have shown that the MCRSC is able to inspect the colon within a time frame of standard colonoscopy.

Micro-intestinal robot with wireless power transmission: design, analysis and experiment

BACKGROUND

Video capsule endoscopy is a useful tool for noninvasive intestinal detection, but it is not capable of active movement; wireless power is an effective solution to this problem.

METHODS

The research in this paper consists of two parts: the mechanical structure which enables the robot to move smoothly inside the intestinal tract, and the wireless power supply which ensures efficiency. First, an intestinal robot with leg architectures was developed based on the Archimedes spiral, which mimics the movement of an inchworm. The spiral legs were capable of unfolding to an angle of approximately 155°, which guaranteed stability of clamping, consistency of surface pressure, and avoided the risk of puncturing the intestinal tract. Secondly, the necessary power to operate the robot was far beyond the capacity of button batteries, so a wireless power transmission (WPT) platform was developed. The design of the platform focused on power transfer efficiency and frequency stability. In addition, the safety of human tissue in the alternating electromagnetic field was also taken into consideration. Finally, the assembled robot was tested and verified with the use of the WPT platform.

RESULTS

In the isolated intestine, the robot system successfully traveled along the intestine with an average speed of 23 mm per minute. The obtained videos displayed a resolution of 320 × 240 and a transmission rate of 30 frames per second. The WPT platform supplied up to 500 mW of energy to the robot, and achieved a power transfer efficiency of 12%.

CONCLUSION

It has been experimentally verified that the intestinal robot is safe and effective as an endoscopy tool, for which wireless power is feasible. Proposals for further improving the robot and wireless power supply are provided later in this paper.