Online Pressure Map Reconstruction in a Multitouch Soft Optical Waveguide Skin (original) (raw)

Soft Multi-point Waveguide Sensor for Proprioception and Extereoception in Inflatable Fingers

2021 IEEE 6th International Forum on Research and Technology for Society and Industry (RTSI), 2021

Disadvantages of conventional robotic systems include rigidity, multiple moving parts, and the need for elaborate safety mechanisms when used in human-machine interaction. Soft manipulators and grippers are gaining in popularity due to being able to handle large payloads whilst being lightweight, highly compliant, low-cost, and compactible or collapsible. Yet soft robots cannot make use of traditional rigid sensors to measure their pose or interaction with the environment. Perception in soft robotics needs to embrace alternative methods: sensors made from soft materials that perform robustly under compression and bending conditions; i.e, stretchable soft sensors that rely on (their) material and electrical properties to output signal measurements. However, many such sensors come with inherent drawbacks, including material incompatibility, fabrication complexity, and hysteresis. In this paper, we report on the use of multiple staggered optical waveguide sensors embedded in silicone. These stretchable optical waveguide sensors coated with a thin layer of gold were fabricated and integrated with a fabric-based, inflatable robot finger. An experimental study was performed to evaluate the sensor's responsiveness. We find that multi-curvature pose estimation (from 0.05-0.135 m-1) (from fully deflated to maximum inflation) can be acquired after integration with the inflatable robot finger. The sensor proves capable of measuring force information by way of interaction with the environment at multiple points along the gripper.

Optomechanics based soft artificial skin

2021

Soft artificial skin capable of sensing touch, pressure and bending similar to soft human skin is important in many modern-day applications including socially interactive robotics, modern healthcare, augmented reality, etc. However, most of the research effort on soft artificial skin are confined to the lab-scale demonstration. We have demonstrated how a fundamental understanding of the contact mechanics of soft material and a specially constructed soft optical waveguide let us develop a highly efficient, resilient, and large-area soft artificial skin for futuristic applications. The soft artificial skin capable of detect touch, load and bending shows extreme sensitivity (up to \({150 \text{k}\text{P}\text{a}}^{-1}\)) to touch, and load, which is 750 times higher than earlier work. The soft-a-skin shows excellent long-term stability i.e. it shows consistent performance up to almost a year. In addition, we describe a 3D printing process capable of producing large areas, large numbers...

The TacTip Family: Soft Optical Tactile Sensors with 3D-Printed Biomimetic Morphologies

Soft Robotics, 2018

Tactile sensing is an essential component in human-robot interaction and object manipulation. Soft sensors allow for safe interaction and improved gripping performance. Here we present the TacTip family of sensors: a range of soft optical tactile sensors with various morphologies fabricated through dual-material 3D printing. All of these sensors are inspired by the same biomimetic design principle: transducing deformation of the sensing surface via movement of pins analogous to the function of intermediate ridges within the human fingertip. The performance of the TacTip, TacTip-GR2, TacTip-M2, and TacCylinder sensors is here evaluated and shown to attain submillimeter accuracy on a rolling cylinder task, representing greater than 10-fold super-resolved acuity. A version of the TacTip sensor has also been open-sourced, enabling other laboratories to adopt it as a platform for tactile sensing and manipulation research. These sensors are suitable for real-world applications in tactile perception, exploration, and manipulation, and will enable further research and innovation in the field of soft tactile sensing.

3D Printable Soft Sensory Fiber Networks for Robust and Complex Tactile Sensing

Micromachines

The human tactile system is composed of multi-functional mechanoreceptors distributed in an optimized manner. Having the ability to design and optimize multi-modal soft sensory systems can further enhance the capabilities of current soft robotic systems. This work presents a complete framework for the fabrication of soft sensory fiber networks for contact localization, using pellet-based 3D printing of piezoresistive elastomers to manufacture flexible sensory networks with precise and repeatable performances. Given a desirable soft sensor property, our methodology can design and fabricate optimized sensor morphologies without human intervention. Extensive simulation and experimental studies are performed on two printed networks, comparing a baseline network to one optimized via an existing information theory based approach. Machine learning is used for contact localization based on the sensor responses. The sensor responses match simulations with tunable performances and good locali...

A Flexible Polymer Tactile Sensor: Fabrication and Modular Expandability for Large Area Deployment

Journal of Microelectromechanical Systems, 2006

In this paper, we propose and demonstrate a modular expandable capacitive tactile sensor using polydimethylsiloxsane (PDMS) elastomer. A sensor module consists of 16 16 tactile cells with 1 mm spatial resolution, similar to that of human skin, and interconnection lines for expandability. The sensor has been fabricated by using five PDMS layers bonded together. In order to customize the sensitivity of a sensor, we cast PDMS by spin coating and cured it on a highly planarized stage for uniform thickness. The cell size is 600 600 m 2 and initial capacitance of each cell is about 180 fF. Tactile response of a cell has been measured using a commercial force gauge having 1 mN resolution and a motorized-axis precision stage with 100 nm resolution. The fabricated cell shows a sensitivity of 3%/mN within the full scale range of 40 mN (250 kPa). Four tactile modules have been successfully attached by using anisotropic conductive paste to demonstrate expandability of the proposed sensors. Various tactile images have been successfully captured by single sensor module as well as the expanded 32 32 array sensors.

Biomimetic tactile sensor array

Advanced …, 2008

The performance of robotic and prosthetic hands in unstructured environments is severely limited by their having little or no tactile information compared to the rich tactile feedback of the human hand. We are developing a novel, robust tactile sensor array that mimics the mechanical properties and distributed touch receptors of the human fingertip. It consists of a rigid core surrounded by a weakly conductive fluid contained within an elastomeric skin. The sensor uses the deformable properties of the finger pad as part of the transduction process. Multiple electrodes are mounted on the surface of the rigid core and connected to impedance-measuring circuitry safely embedded within the core. External forces deform the fluid path around the electrodes, resulting in a distributed pattern of impedance changes containing information about those forces and the objects that applied them. Here we describe means to optimize the dynamic range of individual electrode sensors by texturing the inner surface of the silicone skin. Forces ranging from 0.1 to 30 N produced impedances ranging from 5 to 1000 k . Spatial resolution (below 2 mm) and frequency response (above 50 Hz) appeared to be limited only by the viscoelastic properties of the silicone elastomeric skin.

Flexible Three-Axial Force Sensor for Soft and Highly Sensitive Artificial Touch

Advanced Materials, 2014

using liquid capacitors to address deformability. Here we show the fast and easy fabrication of a fully fl exible capacitive threeaxial force sensor made with conductive fabric electrodes and an elastomeric material. This unique sensor presented a high compliance, robustness and stability under manipulation and very appealing performances in terms of sensitivity (less than 10 mg and 8 µm, minimal detectable weight and displacement, respectively) and detection range (measured up to 190 kPa, and estimated up to 400 kPa) against the existing state-of-the-art sensors. This work intersects with the recent and exciting direction taken by the research fi eld towards smart, integrated, and fl exible electronic devices using an ancestral composite material: textile. [28][29] From less than a decade ago, an increasing number of research efforts have focused on the exploitation of the mechanical properties of textile as a substrate for the absorption or coating of organic and inorganic compounds. Whereas conductive fabrics are today already embraced by fashion and architectural designs, [ 33 ] the textile platform also opens an original means to develop future electronic and sensing devices. Importantly, this research approach holds promise for the design of soft, small sensing elements, wherever high functional integration and low cost are key elements. We used conductive fabrics to develop and validate an original concept of a small and three-dimensional robust sensor. In this work, we demonstrate that the structuring of the dielectric multilayer and the original combination of materials used gives our sensor the potential to outperform state-ofthe-art sensors by employing a fast and accessible yet robust and low-cost fabrication technology. The capacitive sensor is made of two textile electrode levels (i.e., top and bottom) of a non-stretchable copper/tin coated textile (Zelt, Mindset Ltd) separated by a fl oating fl uorosilicone (DowCorning730, 70 µm thickness) fi lm as the dielectric layer ). Its appealing intrinsic dielectric constant and mechanical properties make fl uorosilicone a suitable material for this application. In particular, because of its low adhesion features, an air gap of around 150 µm is naturally formed during fabrication in between the two copper/tin coated textile electrodes. This air gap adds a second dielectric layer to our sensor and triggers very high performances at very low pressures (ca. 0-2 kPa). The woven fabric used in this work presents two main perpendicular sets of conductive yarns (i.e. warp and weft) where the warp yarn is interlaced up and down of the weft yarn creating an opening called shed (see S1, Supporting Information). The volume of air created by the shed contributes to the formation of a third dielectric layer which plays an important role at higher pressures (>2 kPa). This unique composite structure is embedded in between two polydimethylsiloxane (PDMS) packaging layers to form a mechanically fl exible and robust capacitive sensor ). The sensor design has four square The emulation of natural touch requires tactile sensors that mechanically comply with the environment -in order to gain relevant information from physical interactions -and that, at the same time, are able to perform when smoothly adapted to host three-dimensional structures. For this purpose, successive solutions have been attempted. However, to shape deformable materials while developing high precision, yet robust, systems is complex, and it reveals interesting scientifi c questions in addition to technological challenges. As a result, fl exible tactile sensors can present a very high pressure sensitivity, but the low saturation level (less than 50 kPa), intrinsically imposed by their architecture and/or manufacturing technology, limits their applications. Moreover, one fundamental function is still being overlooked, and that is the detection of contact force not only in the normal direction to the sensor/object interface, but also in the tangential direction. This would raise the level of encoded information by an artifi cial touch system closer to natural touch, for instance, slippage and texture detection. However, in comparison to pressure sensitive devices, or combined pressure and strain sensors, only a small number of skin-like sensors that can sense normal and tangential forces has been presented in the literature. In this context, stateof-the-art developments expose two main challenges: on the one hand, highly sensitive and fl exible devices able to detect forces in three dimensions over a large force range are pursued; whereas on the other hand, which is more economically related, their fabrication on large areas is requested. Original alternative sensor designs, using soft materials and processes have been shown to skirt those aspects and/or simplify fabrication processes. Among these, capacitive-based sensors show good potential towards deformable tactile sensors. In particular, Surapaneni et al. have demonstrated very high force range detection (up 320 kPa) and minimum detectable displacement of 60 µm using gold fl oating electrodes in comb-like structures, whereas other groups, in particular, Noda et al. have introduced original approaches for three-axis force detection [+] These authors contributed equally to this work. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

A miniaturized and flexible optoelectronic sensing system for tactile skin

Journal of Micromechanics and Microengineering, 2007

This paper describes the development of a hybrid sensing module consisting of a general purpose electro-optical converter and three MEMS force sensors, to be integrated into flexible substrates for tactile skin applications. The features of the converter, namely its flexible and thin substrate and small dimensions, programmability, optical coding and transmission of the information allow this versatile device to host different sensors, locally preprocess signals, and transmit information robust to electromagnetic noise. After discussing the major technical requirements, the design of the sensing, electrical and optical subsystems is illustrated, as well as the whole process for its fabrication. A first characterization of a working prototype, hosting three MEMS force sensors and nine independent optical channels was performed: the global performances in terms of sensitivity, bandwidth and spatial sensing resolution make the presented module suitable to be used as basic element of a complete tactile system for robotic applications. Several solutions for mass production, improved optical properties and more efficient optical transmission are discussed.

Scalable fabric tactile sensor arrays for soft bodies

Journal of Micromechanics and Microengineering, 2018

Soft robots have the potential to transform the way robots interact with their environment. This is due to their low inertia and inherent ability to more safely interact with the world without damaging themselves or the people around them. However, existing sensing for soft robots has at least partially limited their ability to control interactions with their environment. Tactile sensors could enable soft robots to sense interaction, but most tactile sensors are made from rigid substrates and are not well suited to applications for soft robots which can deform. In addition, the benefit of being able to cheaply manufacture soft robots may be lost if the tactile sensors that cover them are expensive and their resolution does not scale well for manufacturability. This paper discusses the development of a method to make affordable, high-resolution, tactile sensor arrays (manufactured in rows and columns) that can be used for sensorizing soft robots and other soft bodies. However, the construction results in a sensor array that exhibits significant amounts of cross-talk when two taxels in the same row are compressed. Using the same fabric-based tactile sensor array construction design, two different methods for cross-talk compensation are presented. The first uses a mathematical model to calculate a change in resistance of each taxel directly. The second method introduces additional simple circuit components that enable us to isolate each taxel electrically and relate voltage to force directly. Fabric sensor arrays are demonstrated for two different soft-bodied applications: an inflatable single link robot and a human wrist.