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3D Stretchable Inductive Tactile Sensors for Soft Artificial Touch

Periodic Reporting for period 1 - 3D-SITS (3D Stretchable Inductive Tactile Sensors for Soft Artificial Touch)

Reporting period: 2018-09-06 to 2020-09-05

Tactile sensing are crucial for interactive robots and dexterous robotic manipulation, and are playing increasing important in smart surgical instruments, and wearable healthcare systems. Compared to visual and auditory senses, artificial touch sensors are relatively less-developed, due to the complexity of large number of sensing elements required. More crucially, tactile sensors must have both high compliance and high performance to be effectively applied in real-world environments. To survive the wearing and impact due to repeated physical contact, the sensing surface needs to be durable/resilient, while being compliant. In the last decades, remarkable progress has been made in developing 2D flexible sensing skins. A wide variety of different transducer mechanisms have been exploited to date, with common modalities including piezoresistivity/resistance, piezoelectricity, triboelectricity, capacitance, optics/laser, and magnetic field. Nevertheless, challenges remain in developing tactile sensors that can be truly soft (stretchable), durable, robust, and high-performance, ready for real-world applications.
Resistance, capacitance and inductance are the three basic measurand for sensing systems. Compared to resistive and capacitive sensors, inductive sensors are quite overlooked due to the complex readout electronics and coil structure. In this project the fellow intend to investigate the fundamental physics and design principles of the overlooked inductive transducer mechanisms, and the utilization of them in different forms for developing various soft sensors and applications systems. The overall goal of this MSCA-IF project is to develop a robust, high-performance, truly soft, multimodal sensing technology: Stretchable Inductive Tactile Sensors (SITS), enabling them to be directly integrated into soft robots and wearable systems.
This project investigates: a) the working principle and underlying physics, basic characteristics of inductive sensing mechanisms (self-/mutual inductance, eddy-current effect, magnetic reluctance, etc.); b) The design and fabrication techniques of various flexible and stretchable coils; c) Modeling of the inductive coils and sensing devices (numerical analysis and Finite element analysis); d) Development of inductive sensor prototypes and sensing systems; e) Applications of inductive sensing in soft robotics and wearable systems.
The overall objectives of the project are fully achieved, and the research results and outcomes exceed the original plan.
Major Work performed in this 24-month project are:
1. Investigation of Materials and Fabrication Approaches for making Stretchable Coils
2. Developed a Toolbox for Inductive Coil Design and Modeling
3. Invented a novel Folding Angle and Bending Curvature Sensing mechanism by Self-inductance of Planar Coils
4. Developed at least two Inductive Sensing Approaches for Proprioception of Soft Actuators
List of published research results:
1) H. Wang*, S. Veerapandian, M. Totaro, M. Ilyas, M. Kong, U. Jeong, L. Beccai*, “Folding and Bending Planar Coils for Highly Precise Soft Angle Sensing”, Advanced Materials Technologies, vol. 5, 2000659, 2020.
2) H. Wang*, M. Totaro, L. Beccai*, “Toward Perceptive Soft Robots: Progress and Challenges”, Advanced Science, vol. 5, (no. 9), 1800541, 2018
3) H. Wang*, I. Bernardeschi, L. Beccai, “Developing Reliable Foam Sensors with Novel Electrodes”, IEEE Sensors 2019, pp. 246-249, Montreal, QC, Canada, 2019.
4) H. Wang*, M. Totaro, L. Beccai, “Development of Fully Shielded Soft Inductive Tactile Sensors”, The 26th IEEE International Conference on Electronics Circuits and Systems, pp. 246-249, Genoa, Italy, 2019.
5) S. Veerapandian+, W., Jang+, J. B. Seol, H. Wang, K. Thiyagarajan, J. Kwak, G. Park, G. Lee, W. Suh, I. You, M. E. Kılıç, A. Giri, L. Beccai, A Soon*, U. Jeong*, “Hydrogen-Doped Viscoplastic Liquid Metal Microparticles for Stretchable Printed Metal Lines”, Nature Materials, (in press).
6) H. Wang, M. Totaro, A. Astreinidi Blandin, L. Beccai, “A Wireless Inductive Sensing Technology for Soft Pneumatic Actuators Using Magnetorheological Elastomers”, IEEE RoboSoft 2019, pp. 242-248, Seoul, South Korea, 2019.
7) S. Joe, H. Wang, M. Totaro, L. Beccai, “Development of Ultralight Hybrid Pneumatic Artificial Muscle for Large Contraction and High Payload”, IEEE RoboSoft 2020, Yale, New Haven, pp. 27-3, 2020.
8) M. Totaro, I. Bernardeschi, H. Wang, L. Beccai, “Analysis and optimization of fully foam-based capacitive sensors”, IEEE RoboSoft 2020, Yale, New Haven, pp. 470-475, 2020.
Manuscript under-review or being prepared:
• H.Wang* S. Joe, M. Totaro, M. Ilyas, L. Beccai*, “Highly Sensitive Bi-directional Bending Curvature Sensors using Flexible Coils and Ferrite Sheet”, Smart Materials and Structures (to submit).
• S. Joe, H. Wang, M. Totaro, L. Beccai, “Deformation Sensing of vacuum-powered pneumatic artificial muscle via embedded helical coils” (to submit).
• S. Joe, M. Totaro, H. Wang, L. Beccai, “Development of the Ultralight Hybrid Pneumatic Artificial Muscle: modelling and optimization”, Plus One (minor revision)
The results achieved in this project open a new paradigm for soft multimodal sensing in soft robotics and wearables via the various forms of inductive transducers. The developed sensing technologies/solutions offer unique advantages with respect to the state-of-the-art for soft sensing, providing a leap forward in key factors like: sensing performance (resolution, hysteresis, dynamic range etc.), stability, robustness, and easy implementation. Notably, the planar coil-based folding angle and bending curvature sensors is the one of the most elegant sensing solutions to date for such kind of applications, which can be readily stick-on or printed on the sensing surface, insensitive to defects in materials, fabrication and integration of the sensors, at the same time providing highly precise and reliable measurement. The developed planar coil design and analysis toolbox is highly effective and efficient for estimate and optimize coils and coil-based sensors, can it can be very useful for electrical characteristics investigation of flexible and stretchable electronics as well. It will have a substantial impact in years, promoting developments in inductive sensors and sensing solutions, soft electronics, as well as sensing applications in soft robotics and wearable systems.