Soft Pneumatic Gelatin Actuator for Edible Robotics

We present a fully edible pneumatic actuator based on gelatin-glycerol composite. The actuator is monolithic, fabricated via a molding process, and measures 90 mm in length, 20 mm in width, and 17 mm in thickness. Thanks to the composite mechanical characteristics similar to those of silicone elastomers, the actuator exhibits a bending angle of 170.3 {\deg} and a blocked force of 0.34 N at the applied pressure of 25 kPa. These values are comparable to elastomer based pneumatic actuators. As a validation example, two actuators are integrated to form a gripper capable of handling various objects, highlighting the high performance and applicability of the edible actuator. These edible actuators, combined with other recent edible materials and electronics, could lay the foundation for a new type of edible robots.Comment: Submitted to IEEE/RSJ International Conference on Intelligent Robots and Systems 201

Soft Pneumatic Actuator Skin with Piezoelectric Sensors for Vibrotactile Feedback

The latest wearable technologies demand more intuitive and sophisticated interfaces for communication, sensing, and feedback closer to the body. Evidently, such interfaces require flexibility and conformity without losing their functionality even on rigid surfaces. Although there have been various research efforts in creating tactile feedback to improve various haptic interfaces and master–slave manipulators, we are yet to see a comprehensive device that can both supply vibratory actuation and tactile sensing. This paper describes a soft pneumatic actuator (SPA)-based skin prototype that allows bidirectional tactile information transfer to facilitate simpler and responsive wearable interface. We describe the design and fabrication of a 1.4 mm-thick vibratory SPA – skin that is integrated with piezoelectric sensors. We examine in detail the mechanical performance compared to the SPA model and the sensitivity of the sensors for the application in vibrotactile feedback. Experimental findings show that this ultra-thin SPA and the unique integration process of the discrete lead zirconate titanate (PZT)-based piezoelectric sensors achieve high resolution of soft contact sensing as well as accurate control on vibrotactile feedback by closing the control loop

Interactive soft pneumatic actuator skin

The interactive soft pneumatic actuator (SPA) skin is a soft wearable device with integrated actuation and sensing. The SPA skin is a flat flexible patch that can be worn on the body, consisting of a 2-D matrix with independent actuation and sensing elements at each node (a taxel). The SPA skin acts as a bidirectional communication interfacing device. Vibrotactile actuation is achieved using SPAs and the tactile sensing is done via piezo-electric sensors. It can take in input from the user, as well as actuate in various patterns, simulating various sensations such as touch, brush, move, etc. thus allowing a bidirectional communication

An Any-Resolution Distributed Pressure Localization Scheme Using a Capacitive Soft Sensor Skin

We present a method to determine the location of an applied pressure on a large area, monolithic silicone based capacitive sensor. In contrast to pressure sensor arrays composed of n x n discrete sensors, we utilize a single sensor body with a single instrumentation interface to detect n pixels. We interrogate the capacitive sensor at different frequencies, thus modulating the effective length of the sensor. These interrogation frequencies are governed by the sensor’s total capacitance, resistance, and desired spatial resolution of the sensor. We developed an analytical model to calculate the frequency response at different length segments of the sensor and used the results to determine the interrogation frequencies for experimental studies. We performed experimental tests on a 1 x n sensor strip and an n x n sensor sheet and showed that we could attain greater than 90% accuracy in predicting the location of the applied pressure using a model generated by a multi-class kernel support vector machine. This approach towards distributed localization of point pressures greatly reduces the hardware complexity in comparison to discrete sensor arrays and increases the physical robustness of the system

HapBead: on-skin microfluidic haptic interface using tunable bead

On-skin haptic interfaces using soft elastomers which are thin and flexible have significantly improved in recent years. Many are focused on vibrotactile feedback that requires complicated parameter tuning. Another approach is based on mechanical forces created via piezoelectric devices and other methods for non-vibratory haptic sensations like stretching, twisting. These are often bulky with electronic components and associated drivers are complicated with limited control of timing and precision. This paper proposes HapBead, a new on-skin haptic interface that is capable of rendering vibration like tactile feedback using microfluidics. HapBead leverages a microfluidic channel to precisely and agilely oscillate a small bead via liquid flow, which then generates various motion patterns in channel that creates highly tunable haptic sensations on skin. We developed a proof-of-concept design to implement thin, flexible and easily affordable HapBead platform, and verified its haptic rendering capabilities via attaching it to users’ fingertips. A study was carried out and confirmed that participants could accurately tell six different haptic patterns rendered by HapBead. HapBead enables new wearable display applications with multiple integrated functionalities such as on-skin haptic doodles, mixed reality haptics and visual-haptic displays

Flow Path Optimization for Soft Pneumatic Actuators: Towards Optimal Performance and Portability

Soft pneumatic actuators (SPAs) are highly desirable for interactive robotics applications owing to their unconventional properties like high compliance, safe human-machine interaction and adaptable design space. The SPA dynamic behaviour is governed by pneumatic supply systems (PSSs) consisting of source, valve, tubing and fittings. Although their functionality is well known, the inter-dependence of PSS components and their impact on the SPA behaviour has not been quantified, especially in the context of performance and portability. Using the metrics of maximum actuation frequency, air and energy consumption per actuation cycle, here we systematically investigate the effect of five parameters: SPA size, tubing diameter and length, source pressure and valve flow capacity. We model the SPA pressure dynamics model using first principles and define a large study set of 162 model parameter combinations based on commonly used SPAs and PSS components. We then simulate and experimentally measure the maximum actuation frequency in these parameter combinations, while additionally defining experimental protocols for flow characterization of PSS components and valve control strategy for maximizing actuation frequency. Results from experiments and simulations show good agreement, depicting the trends of how different parameters affect SPA performance. An interesting observation was that for a set of SPA size, tubing length and valve flow capacity, there exists a unique optimal tubing diameter that maximizes the actuation frequency. By further analyzing air and energy consumption, this work allows us to define and solve a multi-objective optimization problem to select and control PSS components to optimize SPA performance and portability simultaneously

Design and Computational Modeling of a Modular, Compliant Robotic Assembly for Human Lumbar Unit and Spinal Cord Assistance

Abstract Wearable soft robotic systems are enabling safer human-robot interaction and are proving to be instrumental for biomedical rehabilitation. In this manuscript, we propose a novel, modular, wearable robotic device for human (lumbar) spine assistance that is developed using vacuum driven, soft pneumatic actuators (V-SPA). The actuators can handle large, repetitive loads efficiently under compression. Computational models to capture the complex non-linear mechanical behavior of individual actuator modules and the integrated assistive device are developed using the finite element method (FEM). The models presented can predict system behavior at large values of mechanical deformations and allow for rapid design iterations. It is shown that a single actuator module can be used to obtain a variety of different motion and force profiles and yield multiple degrees of freedom (DOF) depending on the module loading conditions, resulting in high system versatility and adaptability, and efficient replication of the targeted motion range for the human spinal cord. The efficacy of the finite element model is first validated for a single module using experimental results that include free displacement and blocked-forces. These results are then extended to encompass an extensive investigation of bio-mechanical performance requirements from the module assembly for the human spine-assistive device proposed

Closed-Loop Haptic Feedback Control Using a Self-Sensing Soft Pneumatic Actuator Skin

In this article, we achieve a closed-loop control over haptic feedback, first time for an entirely soft platform. We prototyped a novel self-sensing soft pneumatic actuator (SPA) with soft strain sensors, called SPA-skin, which withstands large multiaxial strains and is capable of high-frequency sensing and actuation. To close-loop control the haptic feedback, the platform requires a cohesively integrated system. Our system consists of a stretchable low profile (<500 μm) SPA and an ultra-compliant thin-metal film strain sensor that create a novel bidirectional platform for tactile sensing via force-tunable vibratory feedback. With this prototype, we demonstrated control of the actuator shape in real time up to 100 Hz at output forces up to 1 N, maintained under variable mechanical loadings. We further characterized the SPA-skin platform for its static and dynamic behavior over a range of actuation amplitudes and frequencies as well as developed an analytical model of this system to predict the actuator inflation state only using the embedded sensor's resistance. Our SPA-skin is a multifunctional multilayer system that can readily be implemented as a high-speed wearable bidirectional interface for contact sensing and vibrotactile feedback

A reconfigurable interactive interface for controlling robotic origami in virtual environments

Origami shape transformation is dictated by predefined folding patterns and their folding sequence. The working principle of robotic origami is based on the same principle: we design quasi-two-dimensional tiles and connecting hinges and define and program their folding sequences. Since the tiles are often of uniform shape and size, their final configuration is governed by the kinematic relationship. Mathematicians, computer scientists and even architects have studied a wide range of origami algorithms. However, for multiple shape transformations, the origami design parameters and consequently sequence planning become more challenging. In this work, we present a reconfigurable interactive interface, a physics-based modeling control interface to explore the design space of origami robots. We developed two interactive modes for proof of concept of a bidirectional communication interface between virtual and physical environments. The first interaction mode is origami-inspired, foldable surfaces with distributed sensors that can recreate folding sequences and shape transformations in a virtual environment via hardware-in-loop simulation. Its complementary digital transcription lays the foundation for a robotic origami design tool that provides visual representation of various design formulations as well as an intuitive controller for robotic origami. In the second interaction mode, we construct a physics-based modeling interface for intuitive user manipulation of robotic origami in a virtual environment. Algorithms for graphical representation and command transformation were developed for robotic interaction. Lastly, we tested the efficacy of the algorithms on prototypes to discover the applications and capacities of the reconfigurable interactive interface

Hand and face somatotopy shown using MRI-safe vibrotactile stimulation with a novel soft pneumatic actuator (SPA)-skin interface

The exact somatotopy of the human facial representation in the primary somatosensory cortex (S1) remains debated. One reason that progress has been hampered is due to the methodological challenge of how to apply automated vibrotactile stimuli to face areas in a manner that is: (1) reliable despite differences in the curvatures of face locations; and (2) MR-compatible and free of MR-interference artefacts when applied in the MR head-coil. Here we overcome this challenge by using soft pneumatic actuator (SPA) technology. SPAs are made of a soft silicon material and can be in- or deflated by means of airflow, have a small diameter, and are flexible in structure, enabling good skin contact even on curved body surfaces (as on the face). To validate our approach, we first mapped the well-characterised S1 finger layout using this novel device and confirmed that tactile stimulation of the fingers elicited characteristic somatotopic finger activations in S1. We then used the device to automatically and systematically deliver somatosensory stimulation to different face locations. We found that the forehead representation was least distant from the representation of the hand. Within the face representation, we found that the lip representation is most distant from the forehead representation, with the chin represented in between. Together, our results demonstrate that this novel MR compatible device produces robust and clear somatotopic representational patterns using vibrotactile stimulation through SPA-technology