Design and Characterization of a Multimodal Flexible Electronic Skin with CPLD-Based Data Acquisition for Tactile Intensity and Gesture Recognition.

This work presents the design and characterization of a flexible multimodal electronic skin (e-skin) platform that supports high-resolution tactile sensing and gesture recognition via a CPLD-based data acquisition system. The system integrates a 36-channel, 14-bit hybrid-frequency sampling architecture (2 kHz, 1 kHz, 100 Hz), with hardware-level support for pressure, acceleration, light, temperature, and environmental signals. A flexible FPC substrate enables conformal integration on curved robotic surfaces while maintaining mechanical stability. To demonstrate tactile perception capability, this study focuses on the pressure sensing channel, which serves as the primary modality for contact force estimation and gesture dynamics. Four representative human interactions, gentle touch, tap, light pinch, and strong pinch, were analyzed. Two dimensionless metrics, equivalent waveform skewness and equivalent load, were introduced to distinguish force intensity and gesture categories. Experimental results show that the system achieves clear gesture separation and skin-like viscoelastic response, with an average unloading time of 0.4 s ± 0.2 s. Real-time wireless data transmission at 1.5 Mbps is supported, and the modular design provides a scalable foundation for future integration of additional modalities. This work establishes a hardware framework for force- and gesture-based human-robot tactile interaction, with extendable capacity for multimodal perceptual systems.