Fabrication and Characterization of Additively Manufactured Stretchable Strain Sensors towards the Shape Sensing of Continuum Robots
Daniel Moyer, Wenpeng Wang, Logan Karschner, Loris Fichera, Pratap Rao
AI summary
Problem
Traditional strain gauges cannot withstand the large deformations of continuum robots and are difficult to integrate into their small, flexible bodies, hindering reliable shape sensing.
Approach
The researchers used direct ink writing to fabricate stretchable resistive sensors from three conductive inks and evaluated their electrical response under cyclic bending to identify the most suitable material for robotic integration.
Key results
- Liquid metal sensors showed negligible drift and high linearity (R² > 0.98) across all tested strain conditions
- Silver and carbon elastomer inks exhibited higher gauge factors but suffered from significant resistance drift and nonlinearity at high strains
- Sensors were successfully mounted on millimeter-scale continuum robots for practical shape sensing
- Direct ink writing enabled rapid, low-cost fabrication of stretchable sensors with sub-millimeter trace widths
Why it matters
Enables reliable, miniaturized shape feedback for continuum robots in surgical and industrial applications where traditional sensors fail.
Abstract
This letter describes the manufacturing and exper- imental characterization of novel stretchable strain sensors for continuum robots. The overarching goal of this research is to provide a new solution for the shape sensing of these devices. The sensors are fabricated via direct ink writing, an extrusion- based additive manufacturing technique. Electrically conductive material (i.e., the ink) is printed into traces whose electrical resistance varies in response to mechanical deformation. The principle of operation of stretchable strain sensors is analogous to that of conventional strain gauges, but with a significantly larger operational window thanks to their ability to withstand larger strain. Among the different conductive materials considered for this study, we opted to fabricate the sensors with a high-viscosity eutectic Gallium-Indium ink, which in initial testing exhibited high linearity (R2 ≈0.99), gauge factor ≈1, and negligible drift. Benefits of the proposed sensors include (i) ease of fabrication, as they can be conveniently printed in a matter of minutes; (ii) ease of installation, as they can simply be glued to the outside body of a robot; and (iii) ease of miniaturization, which enables integration into millimeter-sized continuum robots.