Automatic Design Framework of Dielectric Elastomer Actuators: Neural Network-Based Real-Time Simulation, Genetic Algorithm-Based Electrode Optimization, and Experimental Verification.

Dielectric elastomer actuators (DEAs) enable to create soft robots with fast response speed and high-energy density, but the fast optimization design of DEAs still remains elusive because of their continuous electromechanical deformation and high-dimensional design space. Existing approaches usually involve repeating and vast finite element calculation during the optimization process, leading to low efficiency and time consuming. The advance of deep learning has shown the potential to accelerate the optimization process, but the high-dimensional design space leads to challenge on the accuracy and generality of the deep learning model.

Guoying Gu.

Guoying Gu designs bioinspired soft robots, with applications including soft wearable rehabilitation robots, bioinspired robotic systems for grasping and manipulation, and soft sensing systems for human-robot interaction. He discusses the inherently multi-disciplinary nature of soft robotics research and particularly the deep back-and-forth connection with neuroscience.

X-crossing pneumatic artificial muscles.

Artificial muscles are promising in soft exoskeletons, locomotion robots, and operation machines. However, their performance in contraction ratio, output force, and dynamic response is often imbalanced and limited by materials, structures, or actuation principles. We present lightweight, high-contraction ratio, high-output force, and positive pressure-driven X-crossing pneumatic artificial muscles (X-PAMs).

High-Stroke, High-Output-Force, Fabric-Lattice Artificial Muscles for Soft Robots.

Artificial muscles, providing safe and close interaction between humans and machines, are essential in soft robotics. However, their insufficient deformation, output force, or configurability usually limits their applications. Herein, this work presents a class of lightweight fabric-lattice artificial muscles (FAMs) that are pneumatically actuated with large contraction ratios (up to 87.

Dexterous electrical-driven soft robots with reconfigurable chiral-lattice foot design.

Dexterous locomotion, such as immediate direction change during fast movement or shape reconfiguration to perform diverse tasks, are essential animal survival strategies which have not been achieved in existing soft robots. Here, we present a kind of small-scale dexterous soft robot, consisting of an active dielectric elastomer artificial muscle and reconfigurable chiral-lattice foot, that enables immediate and reversible forward, backward and circular direction changes during fast movement under single voltage input. Our electric-driven soft robot with the structural design can be combined with smart materials to realize multimodal functions via shape reconfigurations under the external stimulus.

3D printable high-performance conducting polymer hydrogel for all-hydrogel bioelectronic interfaces.

Owing to the unique combination of electrical conductivity and tissue-like mechanical properties, conducting polymer hydrogels have emerged as a promising candidate for bioelectronic interfacing with biological systems. However, despite the recent advances, the development of hydrogels with both excellent electrical and mechanical properties in physiological environments is still challenging. Here we report a bi-continuous conducting polymer hydrogel that simultaneously achieves high electrical conductivity (over 11 S cm), stretchability (over 400%) and fracture toughness (over 3,300 J m) in physiological environments and is readily applicable to advanced fabrication methods including 3D printing.

Soft Robotics Enables Neuroprosthetic Hand Design.

Development and implementation of neuroprosthetic hands is a multidisciplinary field at the interface between humans and artificial robotic systems, which aims at replacing the sensorimotor function of the upper-limb amputees as their own. Although prosthetic hand devices with myoelectric control can be dated back to more than 70 years ago, their applications with anthropomorphic robotic mechanisms and sensory feedback functions are still at a relatively preliminary and laboratory stage. Nevertheless, a recent series of proof-of-concept studies suggest that soft robotics technology may be promising and useful in alleviating the design complexity of the dexterous mechanism and integration difficulty of multifunctional artificial skins, in particular, in the context of personalized applications.

High-Stretchability, Ultralow-Hysteresis ConductingPolymer Hydrogel Strain Sensors for Soft Machines.

Highly stretchable strain sensors based on conducting polymer hydrogel are rapidly emerging as a promising candidate toward diverse wearable skins and sensing devices for soft machines. However, due to the intrinsic limitations of low stretchability and large hysteresis, existing strain sensors cannot fully exploit their potential when used in wearable or robotic systems. Here, a conducting polymer hydrogel strain sensor exhibiting both ultimate strain (300%) and negligible hysteresis (<1.

Muscle-fiber array inspired, multiple-mode, pneumatic artificial muscles through planar design and one-step rolling fabrication.

Advances in development of artificial muscles have enabled creation of soft robots with biological dexterity and self-adaption in unstructured environments; however, production of scalable artificial muscles with multiple-mode actuations remains elusive. Inspired by muscle-fiber arrays in muscular hydrostats, we present a class of versatile artificial muscles called MAIPAMs (muscle-fiber array inspired pneumatic artificial muscles), capable of multiple-mode actuations (such as parallel elongation-bending-spiraling actuations, 10 parallel bending actuations and cascaded elongation-bending-spiraling actuations). Our MAIPAMs consist of active 3D elastomer-balloon arrays reinforced by a passive elastomer membrane, achieved through a planar design and one-step rolling fabrication approach.

A soft neuroprosthetic hand providing simultaneous myoelectric control and tactile feedback.

Neuroprosthetic hands are typically heavy (over 400 g) and expensive (more than US$10,000), and lack the compliance and tactile feedback of human hands. Here, we report the design, fabrication and performance of a soft, low-cost and lightweight (292 g) neuroprosthetic hand that provides simultaneous myoelectric control and tactile feedback. The neuroprosthesis has six active degrees of freedom under pneumatic actuation, can be controlled through the input from four electromyography sensors that measure surface signals from residual forearm muscles, and integrates five elastomeric capacitive sensors on the fingertips to measure touch pressure so as to enable tactile feedback by eliciting electrical stimulation on the skin of the residual limb.

Cutaneous Ionogel Mechanoreceptors for Soft Machines, Physiological Sensing, and Amputee Prostheses.

Touch sensing has a central role in robotic grasping and emerging human-machine interfaces for robot-assisted prosthetics. Although advancements in soft conductive polymers have promoted the creation of diverse pressure sensors, these sensors are difficult to be employed as touch skins for robotics and prostheses due to their limited sensitivity, narrow pressure range, and complex structure and fabrication process. Here, a highly sensitive and robust soft touch skin is presented with ultracapacitive sensing that combines ionic hydrogels with commercially available conductive fabrics.

Biomimetic Impact Protective Supramolecular Polymeric Materials Enabled by Quadruple H-Bonding.

Nature has been inspiring scientists to fabricate impact protective materials for applications in various aspects. However, it is still challenging to integrate flexible, stiffness-changeable, and protective properties into a single polymer, although these merits are of great interest in many burgeoning areas. Herein, we report an impact-protective supramolecular polymeric material (SPM) with unique impact-hardening and reversible stiffness-switching characteristics by mimicking sea cucumber dermis.

Trimethyltriazine-derived olefin-linked covalent organic framework with ultralong nanofibers.

Two-dimensional (2D) olefin-linked covalent organic frameworks (COFs) with excellent π-electron communication and high stability are emerging as promising crystalline polymeric materials. However, because of the limited species of COFs, their characteristics, processability and potential applications have not been completely understood and explored. In this work, we prepared two novel olefin-linked 2D COFs through Knoevenagel condensation of 2,4,6-trimethyl-1,3,5-triazine with tritopic triazine-cored aldehydes.

Stimuli-responsive functional materials for soft robotics.

Functional materials have spurred the advancement of soft robotics with the potential to perform safe interactions and adaptative functions in unstructured environments. The responses of functional materials under external stimuli lend themselves to programmable actuation and sensing, opening up new possibilities of robot design with built-in mechanical intelligence and unlocking new applications. Here, we review the development of stimuli-responsive functional materials particularly used for soft robotic systems.

Analytical Modeling and Design of Generalized Pneu-Net Soft Actuators with Three-Dimensional Deformations.

Pneu-net soft actuators, consisting of pneumatic networks of small chambers embedded in elastomeric structures, are particularly promising candidates in the society of soft robotics. However, there are few studies on the analytical modeling of pneu-net soft actuators, especially in the three-dimensional space. In this article, based on the minimum potential energy method and the continuum rod theory, we propose an analytical model and corresponding design approach for a class of generalized pneu-net soft actuators (gPNSAs) with both bending and twisting deformations by combining the geometric complexity and material elasticity.

Mechanical Effect on Gene Transfection Based on Dielectric Elastomer Actuator.

Gene transfection has been widely applied in genome function and gene therapy. Although many efforts have been focused on designing carrier materials and transfection methods, the influence of mechanical stimulation on gene transfection efficiency has rarely been studied. Herein, dielectric elastomer actuator (DEA)-based stimulation bioreactors are designed to generate tensile and contractile stress on cells simultaneously.

Design of 3D Printed Programmable Horseshoe Lattice Structures Based on a Phase-Evolution Model.

By 3D printing lattice structure with active materials, the structures can exhibit shape and functional changes under external stimulus. However, the programmable shape changes of the 3D printed lattice structures are limited due to the complex geometries, nonlinear behaviors of the active materials, and the diverse external stimuli. In this work, we propose a design framework combining experiments, theoretical modeling, and finite element simulations for the controllable shape changes of the 3D printed horseshoe under thermal stimulus.

Design, Modeling, and Evaluation of Fabric-Based Pneumatic Actuators for Soft Wearable Assistive Gloves.

Textile fabrics are compliant, lightweight, and inherently anisotropic, making them promising for the design of soft pneumatic actuators. In this article, we present the design, modeling, and evaluation of a class of soft fabric-based pneumatic actuators (SFPAs) for soft wearable assistive gloves that can simultaneously assist the thumb abduction and finger flexion and extension motions for brachial plexus injury patients. We investigate the mechanical behaviors of various woven fabrics and rib weft-knitted fabric structures, guiding us to design a thumb-abduction SFPA, a finger-flexion SFPA, and a finger-extension SFPA.

Cell Nanomechanics Based on Dielectric Elastomer Actuator Device.

As a frontier of biology, mechanobiology plays an important role in tissue and biomedical engineering. It is a common sense that mechanical cues under extracellular microenvironment affect a lot in regulating the behaviors of cells such as proliferation and gene expression, etc. In such an interdisciplinary field, engineering methods like the pneumatic and motor-driven devices have been employed for years.

Stretchable elastic synaptic transistors for neurologically integrated soft engineering systems.

Artificial synaptic devices that can be stretched similar to those appearing in soft-bodied animals, such as earthworms, could be seamlessly integrated onto soft machines toward enabled neurological functions. Here, we report a stretchable synaptic transistor fully based on elastomeric electronic materials, which exhibits a full set of synaptic characteristics. These characteristics retained even the rubbery synapse that is stretched by 50%.

Fractional repetitive control of nanopositioning stages for tracking high-frequency periodic inputs with nonsynchronized sampling.

The repetitive control (RC) has been employed for high-speed tracking control of nanopositioning stages due to its abilities of precisely tracking periodic trajectories and rejecting periodic disturbances. However, in digital implementation, the sampling frequency should be integer multiple of the tracking frequency of the desired periodic trajectory. Otherwise, the rounding error would result in a significant degradation of the tracking performance, especially for the case of high input frequencies.

Modeling the Viscoelastic Hysteresis of Dielectric Elastomer Actuators with a Modified Rate-Dependent Prandtl⁻Ishlinskii Model.

Dielectric elastomer actuators (DEAs) are known as a type of electric-driven artificial muscle that have shown promising potential in the field of soft robotics. However, the inherent viscoelastic nonlinearity makes the modeling and control of DEAs challenging. In this paper, we propose a new phenomenological modeling approach with the Prandtl⁻Ishlinskii (P⁻I) model to characterize the viscoelastic hysteresis nonlinearity of DEAs.

Integrated Soft Ionotronic Skin with Stretchable and Transparent Hydrogel-Elastomer Ionic Sensors for Hand-Motion Monitoring.

Skin-like stretchable sensors with the flexible and soft inorganic/organic electronics have many promising potentials in wearable devices, soft robotics, prosthetics, and health monitoring equipment. Hydrogels with ionic conduction, akin to the biological skin, provide an alternative for soft and stretchable sensor design. However, fully integrated and wearable sensing skin with ionically conductive hydrogel for hand-motion monitoring has not been achieved.