Improving Sensing Coverage and Compliance of 3D-Printed Artificial Skins Through Multi-Modal Sensing and Soft Materials
Abstract Overview
This paper presents a 3D-printed artificial skin that combines time-of-flight (ToF) and self-capacitance (SC) sensing to improve tactile and proximity coverage on robot bodies. The system uses a procedural, form-fitting fabrication workflow implemented in Blender geometry nodes and integrates a soft TPU covering intended to add compliance, protect electronics, and support pressure-correlated tactile responses. The authors introduce a threaded insert interface to connect printed conductive traces to the microcontroller without external wiring to the SC sensors. The approach is demonstrated on a Franka FR3 arm using six skin units with 40 hybrid sensing elements, with the two modalities running in parallel without signal fusion.
Novelty
The main novelty is the integration of hybrid ToF and SC sensing within a scalable 3D-printed artificial skin that also incorporates soft compliant TPU materials, whereas prior 3D-printed skins were limited to unimodal sensing and rigid components. The work is additionally distinctive in its threaded insert design that eliminates ad hoc external wiring for the printed SC sensors, addressing signal drift issues caused by wire bending.
Results
The authors deploy six artificial skin units with 40 sensing elements on an FR3 robot arm and show that the distributed ToF sensors can reconstruct dynamic scenes as a point cloud. Capacitive sensing experiments show that contact detection SNR remains above the stated minimum threshold of 7 in all tested configurations (with/without ToF sensors and with/without the compliant covering), though the presence of ToF sensors and the covering each reduce SNR compared to baseline. The capacitive signal magnitude increases when the covering is squeezed, supporting a pressure-correlated tactile response.
Key Points
- A hybrid 3D-printed skin combines ToF proximity sensing (up to 4 m range, 8×8 grids at 12 Hz) and self-capacitance sensing (42 ± 2 Hz) to extend observable range from close contact to farther-distance perception, though the two modalities run in parallel without fusion.
- A soft TPU covering is integrated into the printed skin to improve compliance and impact absorption; while it reduces the resting capacitive SNR by increasing the distance between the hand and SC sensors, squeezing the covering increases the signal, demonstrating pressure-correlated tactile response.
- On an FR3 arm, six skin units with 40 sensing elements support scene reconstruction via ToF point clouds and maintain capacitive contact detection above the minimum SNR threshold of 7 across all tested configurations, with SNR ranging from 13 ± 3 (covering at rest with ToF) to 120 ± 20 (no covering, no ToF).