An Origami-Inspired Endoscopic Capsule with Tactile Perception for Early Tissue Anomaly Detection

TL;DR

This work tackles early detection of small intestinal nodules, a challenge for conventional capsule endoscopy. It introduces an origami-inspired capsule with four piezoresistive tactile sensors and a particle-filter–based detection framework, leveraging templates to recognize nodules and estimate their size. The origami skin enables passive propulsion under peristalsis, allowing systematic re-positional sensing along the intestinal tract. In a 2D Ecoflex intestine phantom, the system reliably detects nodules down to $2$ mm and provides size estimates within a practical ±$1$ mm tolerance, highlighting potential for earlier GI cancer screening with tactile sensing instead of sole imaging.

Abstract

Video Capsule Endoscopy (VCE) is currently one of the most effective methods for detecting intestinal diseases. However, it is challenging to detect early-stage small nodules with this method because they lack obvious color or shape features. In this letter, we present a new origami capsule endoscope to detect early small intestinal nodules using tactile sensing. Four soft tactile sensors made out of piezoresistive material feed four channels of phase-shifted data that are processed using a particle filter. The particle filter uses an importance assignment template designed using experimental data from five known sizes of modules. Moreover, the proposed capsule can use shape changes to passively move forward or backward under peristalsis, enabling it to reach any position in the intestine for detection. Experimental results show that the proposed capsule can detect nodules of more than 3mm diameter with 100% accuracy.

Figures (7)

• Figure 1: Conceptual overview of origami capsule for early detection of intestinal tissue anomaly. (A) When the origami structure of the capsule is unfolded, it is continuously propelled forward by the peristalsis of the intestine. (B) The origami structure also serves as a flexible pressure sensor. As the capsule moves forward, intestinal pressure data is continuously collected. Potential nodule signals can be analyzed using an algorithm. (C) Once a signal resembling a nodule is detected, the origami structure will be folded up by an actuator inside the capsule. (D) The folded origami structure will be pushed backward by intestinal peristalsis, returning to the location of the abnormal signal for retesting to improve diagnostic accuracy.
• Figure 2: Origami structure fabrication method. (A) $4$ Independent origami substructures were printed using an FDM printer. The filament was conductive EelTM TPU. (B) The origami substructure was cut along the dotted line. (C) An enamelled copper wire was inserted into each cut end of the substructure. (D)-(E) The cut part of the substructure was reattached using cyanoacrylate adhesive. (F)-(G) 4 substructures were glued together to form a complete origami structure.
• Figure 3: Overall experiment set-up. We tested the origami sensor in a two-dimensional intestinal simulator. Two silicone intestinal walls were made of EcoflexTM 00-10. A sphere made of rubber was placed under the intestinal wall to simulate a nodule. Peristalsis was generated by squeezing the intestinal walls with cam mechanisms. The silicone sheet placed between the cam and the intestinal wall was used to make the peristalsis more elastic. The speed of peristalsis can be adjusted by controlling a 28BYJ-48 stepper motor rotation through Arduino UNO. Arduino Mega 2650 was used to record the resistance of each sensor unit on the origami sensor.
• Figure 4: The data pre-processing process. (A) In the case of a healthy intestine without a nodule: (A)(1) Original signal from a healthy intestine without a nodule, (A)(2) RMS envelope (window size $W = 84$) result of the signal, (A)(3) Matrix formed by merging the signals from four sensors. (B) In the case of an intestine with a nodule: (B)(1) Original signal from an intestine with a nodule, (B)(2) RMS envelope result showing that the sensors sequentially detect a sharp increase in abnormal pressure, (B)(3) A matrix where a distinctive pattern is visible, indicating the presence of a nodule.
• Figure 5: The templates include the template without nodules ($\mathbf{T}^0$) and the templates for nodules of sizes $1$ mm to $5$ mm ($\mathbf{T}^1$ to $\mathbf{T}^5$). The visualization of templates includes contour lines to facilitate observing their differences.