Battery-Free Tattooing Mechanism-Based Functional Active Capsule Endoscopy

Abstract

This paper presents a novel tattooing capsule endoscope (TCE) for delivering a certain amount of ink to the submucosal layer of digestive tract organs. A dual-function permanent magnet is used for locomotion and injection activation. The developed capsule endoscope can move actively in 5 DOF due to the interaction between the permanent magnet and a controllable external magnetic field produced by an electromagnet actuation system. In addition, the permanent magnet is involved in a specially designed mechanism to activate a process that creates a squeezing motion to eject the liquid from the storage room to the target. The dimension of the prototype is 12.5 mm in diameter and 34.6 mm in length. The proposed TCE is tested ex vivo using a fresh porcine small-intestine segment. We were able to direct the TCE to the target and deliver the tattoo agent into the tissue. The proposed mechanism can be used for drug delivery or lesion tattooing, as well as to accelerate the realization of the functional capsule endoscope in practice.

Keywords: active capsule endoscope; gastrointestinal tract diagnosis; tattooing function.

Figure A1

Drawing of the head dome.

Figure 1

(a) Overall description of the TCE system and (b) conceptual design of the TCE in isometric view. D (=2 to 5 cm) is the recommended tattoo distance. Mx 1 is Maxwell coil aligned along the y-axis, Mx 2 is Maxwell coil aligned along the z-axis, HH is the Helmholtz coil aligned along the y-axis, RC 1 and RC 2 are customized rectangular coils arranged in four quarters of the xz plane.

Figure 2

(a) Transparent view of the tattooing module inside capsule shell. (b) Detailed design of the tattooing module with components: 1, injection needle; 2, module body; 3, rubber piston; 4, permanent magnet guidance; 5, water reservoir; 6, microneedle; 7, helical spring; 8, four-rod pad to squeeze water; 9, cubic permanent magnet. (c) Isometric view of the water squeezing module.

Figure 3

Design of the needle management module with the head dome (left) and control mechanism (right). The blue arrow indicates the rotation magnetic field direction B. A drawing of the head dome is shown in Appendix A.

Figure 4

Fabrication of a TCE prototype: (a) 3D printing components; (b) assembled 4-rod pad with microneedle and helical spring; (c) assembled tattooing module with back view (left) and top view (right); (d) assembled TCE.

Figure 5

Scheme of experiment setup. The tattooing capsule was controlled by the magnetic field using a keyboard and a joystick. The controlled parameters were computed by the control software in the computer. The power supplies were used to provide a current to each coil using the control command via the software.

Figure 6

(a) Experimental setup to investigate the required force to deliver ink into the tissue of the pig’s colon (top) and results (bottom). (b) Experiment setup with a diagram to estimate the force on a piston generated by the chemical reaction (top) and results (bottom).

Figure 7

(a) Configuration setup to measure the magnetic force produced by the EMA system. (b) The results of the magnetic force and defined values for working modes of TCE.

Figure 8

Validation of the triggering mechanism to release ink.

Figure 9

The 5 DOF locomotion of the TCE robot: (a) yaw motion; (b) roll motion (a yellow marker on capsule was used to recognize the roll motion); (c) x-axis translation; (d) y-axis translation; (e) z-axis translation.

Figure 10

Experiment result of the proposed tattooing capsule endoscope in a segment of small intestine: (a) capsule locomotion; (b) needle extrusion; (c) tattooing and needle retraction. RtE means Rotate to Extrude. Blue and red arrows depict the magnetic field and force direction, respectively.