Stretchable, Multiplexed, and Bimodal Sensing Electronic Armor for Colonoscopic Continuum Robot Enhanced by Triboelectric Artificial Synapse

Abstract

Colonoscopic continuum robots often lack sensing capabilities, risking tissue damage. An ideal robot electronic skin should offer full-body coverage, multiplexing, stretchability, and multifunctionality, but integration is challenging due to the robot's elongated structure. This work presents a stretchable electronic armor (E-armor) with a 3D crosslinked structure that enables 300 mm full coverage while accomplishing multiplexed simultaneous tactile and strain sensing through bioinspired artificial synapse mechanisms. The E-armor integrates 48 tactile sensing points through bilayer co-electrode strategy, reducing wiring while combining triboelectric encoding intelligence with innovative stretchable triboelectric interlinked films (TIFs) to form a triboelectric artificial synapse that generates digitally encoded signal pairs upon contact. A convolutional neural network and long short-term memory network (CNN-LSTM) deep learning framework achieve 99.31% accuracy in identifying multi-point tactile signals. A sodium alginate/polyacrylamide/sodium chloride (SA/PAM/NaCl) conductive hydrogel serves as a strain sensing element, providing excellent stretchability and biocompatibility, and allowing precise inference of bending angles at 12 strain sensing edges. A compliance control strategy coordinates tactile and strain signals to autonomously adjust continuum robot postures while ensuring smooth operation. The digital twin-based 3D visualization interface enhances human-robot interaction by digitally reconstructing both tactile and strain feedback, enabling real-time visualization of the continuum robot's intracolonic posture.

Keywords: colonoscopic continuum robot; full‐coverage; multiplex; strain sensing; stretchable electronic armor; tactile sensing; triboelectric encoding.

Figure 1

Proposed E‐armor based on a bimodal and triboelectric encoding strategy for colonoscopy examinations. a) Schematic illustration of multiple sensory receptors in animal skin for tactile perception. b‐i) Concept of an intelligent colonoscopic continuum robot. b‐ii) Schematic of the E‐armor unit structure. c) Strain sensing strategy of the E‐armor. c‐i) Schematic of the strain sensing net. c‐ii) Structure of the SA/PAM/NaCl hydrogel. c‐iii) Strain signal output and posture perception strategy of the continuum robot. d) Tactile sensing strategy of the E‐armor. d‐i) Schematic of the tactile sensing net. d‐ii) TENG effect between PTFE‐Ecoflex and PA‐Ecoflex. d‐iii) Tactile signal output and digital encoding strategy of the E‐armor. e) Autonomous navigation of the continuum robot with integrated E‐armor, incorporating bimodal information closed‐loop feedback.

Figure 2

Digital encoding strategy of E‐armor tactile sensing signals. a) Working mechanisms of tactile sensing. b) TENG signal waveforms generated by PTFE‐Ecoflex and PA‐Ecoflex. c) Digital encoding strategy of E‐armor unit tactile sensing signal. c‐i) Naming convention for tactile sensing points. c‐ii) Digital encoding strategy for a single‐point contact. c‐iii) Digital encoding strategy of multi‐point contact. c‐iv) Digital encoding of tactile signals exemplified by P9. c‐v) Digital encoding of tactile signals exemplified by simultaneous contact with P1 and P5. c‐vi) Digital encoding of tactile signals exemplified by simultaneous contact with P2, P6, and P10. c‐vii) Real‐time voltage signal waveforms corresponding to examples (c‐iv–vi). d) Real‐time voltage waveforms of the TENG tactile signal under four cases of contact. e) Confusion matrices showing classification accuracy using the CNN‐LSTM model. f) 2D point cloud visualization using t‐SNE for signal classification.

Figure 3

Strain sensing performance and continuum robot posture recognition strategy of the E‐armor. a) Working mechanisms of strain sensing. b) Relationship between the relative resistance change rate and strain of the sensing belt. c) Hysteresis of the sensing belt. d) Continuum robot bending posture recognition strategy for the joint of the E‐armor unit. d‐i) Naming of the four sensing belts on the E‐armor unit. d‐ii–v) Relationship between the bending direction of continuum robot joint and the relative resistance change rates. e) Naming convention and schematic of bending angles for E‐armor units on continuum robot. f) Relationship between the relative voltage change rate of the E‐armor unit and the bending angle of continuum robot single joint. g) Posture recognition of single‐joint and multi‐joint configurations in continuum robots using the E‐armor.

Figure 4

Compliance control strategy and autonomous navigation of a continuum robot integrated with E‐armor in an intestine‐shaped acrylic pipeline. a) Compliance control strategy of continuum robot. b) Demonstration of the compliance control of single‐point on Joint #1. b‐i) Screenshot of the contact point P4 on Joint #1. b‐ii) Tactile signals of the contact point P4 on Joint #1. b‐iii) Strain signals of the contact point P4 on Joint #1. c) Demonstration of the compliance control of single‐point on Joint #2. c‐i) Screenshot of the contact point P6 on Joint #2. c‐ii) Tactile signals of the contact point P6 on Joint #2. c‐iii) Strain signals of the contact point P6 on Joint #2. d) Demonstration of the compliance control of multi‐point on Joint #1. d‐i) Screenshot of the contact points P8 and P12 on Joint #1. d‐ii) Tactile signals of the contact points P8 and P12 on Joint #1. d‐iii) Strain signals of the contact points P8 and P12 on Joint #1. e) Demonstration of the compliance control of Joint #2 and Joint #3. e‐i) Screenshot of the contact points P4 on Joint #2 and P6 on Joint #3. e‐ii) Tactile sensing signals of the contact points P4 on Joint #2 and P6 on Joint #3. e‐iii) Strain sensing signals of the contact points P4 on Joint #2 and P6 on Joint #3.

Figure 5

Adaptive crawling and digital‐twin‐based 3D posture visualization interface of continuum robot within silicone intestine model. a) Process of the digital‐twin‐based 3D posture visualization interface for continuum robot. b) Comparison between invisibility and visualization of continuum robot postures, along with display of tactile sensing points, under the scenarios of b‐i) single‐joint single‐point contact, b‐ii) single‐joint multi‐point contact, and b‐iii) multi‐joint multi‐point contact. c) Display of strain sensing signals of the continuum robot during adaptive crawling through silicone intestine model.