Robots have already become an indispensable part of our lives. However currently, most robots are relatively rigid machines which make unnatural movements. Inspired by living organisms, soft material robotics hold great promise for areas where robots need to contact and interact with humans, such as manufacturing and healthcare. Unlike rigid robots, soft robots can replicate natural motion – grasping and manipulation – to provide medical and other types of assistance, perform delicate tasks, or pick up soft objects
Soft robotics differ from traditional counterparts in some important ways: Soft robots have little or no hard internal structures. Instead they use a combination of muscularity and deformation to grasp things and move about. Rather than using motors, cables or gears, soft robots are often animated by pressurized air or liquids. In many cases soft robotics designs mimic natural, evolved biological forms hence also called bio-inspired robots. This, combined with their soft exteriors, can make soft robots more suitable for interaction with living things or even for use as human exoskeletons.
The emerging field of soft robotics aims to improve robot/human interactivity promising to bring robots into all aspects our daily lives, including wearable robotics, surgical robots, micromanipulation, search and rescue, and others. Soft robots can become aides for the disabled or the elderly if they can be trusted not to hurt the people they come into contact with. Miniature soft robots could even serve as surgical tools inside the body.
“There is a great need in the health care system for lightweight, lower-cost wearable exoskeleton designs to support stroke patients, individuals diagnosed with multiple sclerosis and senior citizens who require mechanical mobility assistance,” said Larry Jasinski, CEO of ReWalk. Currently in the United States, there are an estimated 3 million stroke patients and 400,000 MS patients who are suffering from limited mobility due to lower limb disabilities.
Many industries are searching for new ways to use robots, including developing machines that can work alongside humans and those that are more versatile than the single-task assembly line bots of years past. Company Soft Robotics has developed fingerlike grippers are made of flexible material, such as silicone, and powered by compressed air especially useful in warehouse and assembly line markets — particularly in the food industry, where robots aren’t typically trusted to handle delicate items like fresh produce.
They are crucial in the systems that deal with uncertain and dynamic task-environments, e.g. grasping and manipulation of unknown objects, locomotion in rough terrains such as ocean floor, and physical contacts with living cells and human bodies. These robots must move over rough terrain without getting stuck and need manipulators that can grab whatever strangely shaped Soft and deformable structure objects they encounter. Robots with greater flexibility could also help in military operations, where level terrain and unobstructed areas are rare, whether as a fully intact robot or as, say, a strap-on arm with a pneumatically controlled hand that could extend the reach, strength or capability of what a person could do.
Scientists are also studying how soft robots could lead to major breakthroughs in the development of self-repairing, growing and self-replicating robots, according to the IEEE Robotics and Automation Society. Borgatti explained how soft robots can react to their environments – a major factor for future government use. For example, soft robots can be designed to navigate difficult terrain like shifting sand and fall without being damaged – picking themselves up and correcting their course.
Soft Robotics arms can come in handy when carrying these soldiers without causing injury. “We have lost medics throughout the years because they have the courage to go forward and rescue their comrades under fire. With the newer technology, with the robotic vehicles we are using even today to examine and to detonate IEDs [improvised explosive devices], those same vehicles can go forward and retrieve casualties,” Major General Steve Jones, commander of the Army Medical Department Center, said. Evacuating casualties was only one of the roles for robots in battlefield medicine that Jones discussed. Another option is delivering medical supplies to dangerous areas, supporting troops operating behind enemy lines.
“Despite its importance and considerable demands, the field of Soft Robotics faces a number of fundamental scientific challenges: the studies of unconventional materials are still in their exploration phase, and it has not been fully clarified what materials are available and useful for robotic applications; tools and methods for fabrication and assembly are not established; we do not have broadly agreed methods of modeling and simulation of soft continuum bodies; it is not fully understood how to achieve sensing, actuation and control in soft bodied robots; and we are still exploring what are the good ways to test, evaluate, and communicate the soft robotics technologies,” says IEEE Robotics and Automation Society.
Artificial muscles are the core components of the smart and interactive soft robotic systems, providing the capabilities in shape morphing, manipulation, and mobility. To enable artificial muscles which can reproduce similar functionalities or even surpass the performances of their natural counterparts in some aspects is the major goal for the development of artificial muscles and their deployments in the real‐world applications.
Natural muscles provide salient features of large stress of ≈0.35 MPa, high conformability with strain above ≈20%, high peak output power of 323 W kg–1, excellent mechanical stability with billions of repetitive contraction cycles, and utilization of renewable biological fuel energy with high efficiency (≈40%). To enable artificial muscles which can reproduce similar functionalities or even surpass the performances of their natural counterparts in some aspects is the major goal for the development of artificial muscles and their deployments in the real‐world applications.
Soft robotics has made leaps and bounds over the last decade as researchers around the world have experimented with different materials and designs to allow once rigid, jerky machines to bend and flex in ways that mimic and can interact more naturally with living organisms. However, increased flexibility and dexterity has a trade-off of reduced strength, as softer materials are generally not as strong or resilient as inflexible ones, which limits their use. Due to the soft materials used, these robots can not only squeeze into tight spaces, but also recover more easily from collisions and pick up and handle irregularly-shaped objects. However, because of soft robots’ flexibility, they often struggle with correctly measuring where an object is, or whether they actually picked the object up.
The university research is focused on developing new materials like dielectric elastomers, carbon nanotube yarn and self-healing materials and on designing the controllers and actuators that animate them. New actuator technologies and fabrication approaches will bring about better force-speed operating points, variable impedance, more convenient form factors, and actuators without transmission mechanisms.
Characterizing and predicting the behavior of soft multi-material actuators is challenging due to the nonlinear nature of both the hyper-elastic material and the large bending motions they produce. Key challenges in the design and manufacture of soft robots include the complex fabrication processes and the interfacing of soft and rigid components.
While the initial investigations on artificial muscles have been focused on enabling soft actuators with improved mechanical performances, there is a clear shift in recent years to integrate soft functional electronic devices, including the sensing devices which can perceive external stimulus such as strain, pressure, and temperature etc. and the responding device which can provide interactive feedbacks to the users such as emissive surfaces, color changes, and acoustic outputs etc., to impart mechanical intelligence in the soft actuators. Fully soft sensors that can be incorporated into the actuator design during the manufacturing process are needed to control soft actuators; they provide means of monitoring their kinematics, interaction forces with objects in the environment and internal pressure.
Number of researchers have been investigating unconventional materials for robotic systems, in which soft materials such as polymer based materials are examined for novel sensory devices and actuators. The newly developed smart materials, sensors and actuators were then integrated into micro-robots of various kinds. Also the flexible body structures of animals were replicated in the reconfigurable robots.
Integration with Functional Devices
Biological systems actively adapt or interact with the natural environments using their capabilities to sense external stimulus and interact with responsive outputs. The artificial muscles, which are yet passively morphing, provide the platform to integrate the sensing and responding electronic components to enable smart and interactive soft robotic systems, bridging the gap for their real‐world applications with human and environment interactions.
It is an exciting and highly challenging research scope which will require interdisciplinary research efforts to integrate functional electronic components with the soft and deformable artificial muscles to mimic the functionalities of biological creatures, including the capabilities to perceive external stimulus including strain, pressure, and temperature etc. and provide responsive feedbacks including emissive surface, color change, and acoustic output etc.
Similarly, capacitive strain sensors and pressure sensors can be fabricated by sandwiching a dielectric layer between two stretchable electrodes. The capacitance changes from the devices can be monitored to measure the mechanical inputs.Dielectric Elastomer Actuators (DEA)s share similar device configuration with these sensing devices. The DEA can be considered as a soft and deformable capacitor, which can change its capacitance due to the dimension changes of the dielectric layer under mechanical strains. As an example, the self‐sensing capability of the DEA can be utilized to achieve a robotic arm with simultaneous actuating and sensing performances.
Integration with Sensing
Inspired by the human skins’ sensing capabilities, enabling the exteroception of the input stimulus, especially in strain, pressure and temperature, has been carried out to improve the operations of soft robotics in manipulation, locomotion, and interaction. The lack of compliance in the conventional sensing electronics is the limiting factor for their systematic integration with the soft robotics. Advancement in the soft sensing electronics has provided the paradigm to explore different integration methods.
Exploring the self‐sensing capability of the soft actuators, which can be realized by the intrinsic sensing properties from the active materials or the device structures, is the most direct approach to integrate the sensing capabilities in the soft robotic systems. It can significantly reduce complexity of the integrated systems and avoid the interfacing problems between different devices. For instance, piezoresistive materials can be used to measure the mechanical deformations by the changes of their resistances.
Some of the active materials for the soft actuators are also piezoresistive materials at the same time. As a result, the inherent sensing capability in these soft actuators can be explored without the requirement to integrate the strain sensing devices. As an example, a bilayer of reduced graphene oxide (RGO) and biaxially oriented polypropylene (BOPP) can simultaneously demonstrate large bending actuation and strain sensing performance.
Apart from utilizing the self‐sensing capabilities of the soft actuators, systematical integration of sensing devices with the soft actuators is an alternative approach, which can enable more functionalities in the systems. Lewis’s group has realized a soft somatosensitive actuator which is capable of haptic and temperature sensing by integrating stretchable pressure and temperature sensing devices with the soft pneumatic actuators.
Integration with Response
Compared to the electronic systems which use electrical and electromagnetic signals to communicate, biological systems communicate in a much different way. Development of the way and strategy that the smart and interactive soft robotic systems can response and communicate with the users is pivotal to facilitate their applications in the real‐world environments.
Color change is a communication art mastered by biological systems to deliver massive information in a most effective way. For instance, a seahorse uses changes of its skin color to frighten predators and communicate emotions. Chameleons can change their colors to camouflage into the surrounding environments. Acoustic information is another key method that living organisms utilize to communicate. Taking inspiration from the communication approaches in the biological systems, the integration of color changes and acoustic output with the soft actuators have been intensively explored to enable effective interaction and communication for the smart and interactive robotic systems.
Color changes can be achieved in many different ways, which can be categorized as emissive and nonemissive approaches. Stretchable emissive devices have gained significant progress in recent years, which have been realized by assembling conventional rigid light‐emitting components onto elastic substrate or by adhering ultrathin light‐emitting devices onto prestrained elastomeric substrates. Alternatively, intrinsically stretchable emissive devices can also be realized by developing intrinsically stretchable light‐emitting materials based on light‐emitting electrochemical cell or alternating‐current electroluminescent (ACEL) materials. Stretchable ACEL device has the advantages of simple device architecture and excellent emission stability under mechanical strains, making it an ideal candidate for integration with soft actuators.
Different from the emissive devices, nonemissive devices utilize the changes in the light reflected from or transmitted through the materials to modulate their colors. Materials with different color switching mechanisms have been reported, including electrochromic (EC) devices (color change with the electrochemical effects), mechanochromic devices (color change with mechanical deformations), thermochromic devices (color change under different temperatures), and photochromic (color change under light irradiation) etc.
Acoustic output is generated by high frequency mechanical vibration. Consequently, a sound generation device can be considered as an actuator working in the high frequency range. Actuators based on the electromagnetic, electrostatic, and piezoelectric devices are generally used for the high‐frequency vibrations generation. Unlike the color changing materials which may require appreciable feature sizes in the device in order to be easily perceived by the users, the conventional rigid acoustic devices could be directly integrated into the soft robotic systems when their size is considerable small compared to that of the soft systems. Nevertheless, the capability to develop stretchable acoustic devices is still necessary in small soft robotic systems where their size can no longer be ignored.
MIT builds a robot hand that can see and feel objects
Robotic hands capable of picking up objects as fragile as a crisp by “sensing” objects have been developed by researchers. Two new tools built by MIT‘s Computer Science and Artificial Intelligence Laboratory (CSAIL) offer a breakthrough in the emerging field of soft robotics – a new generation of robots that use squishy, flexible materials rather than traditional rigid equipment. These types of soft robots often draw inspiration from living organisms and offer numerous benefits in their versatile functionality. They are able to operate far more delicately than their rigid counterparts, but until now they have lacked the ability to perceive what items they are interacting with.
To overcome this, the researchers equipped their robots with various sensors, cameras and software, allowing them to “see and classify” a range of objects. “We wish to enable seeing the world by feeling the world,” said MIT professor and CSAIL director Daniela Rus. “Soft robot hands have sensorized skins that allow them to pick up a range of objects, from delicate, such as potato chips, to heavy, such as milk bottles.”
By adding tactile sensors, the robot was able to understand what it was picking up and adjust the amount of pressure exerted accordingly. Of the 10 objects used in the experiment, the sensors were able to identify them with an accuracy rate of more than 90 per cent.
“Unlike many other soft tactile sensors, ours can be rapidly fabricated, retrofitted into grippers, and show sensitivity and reliability,” said MIT’s Josie Hughes, the lead author of a paper detailing the sensors. “We hope they provide a new method of soft sensing that can be applied to a wide range of different applications in manufacturing settings, like packing and lifting.” The second robot made use of an innovative “GelFlex” finger, which uses a tendon-driven mechanism and an array of sensors to provide “more nuanced, human-like senses”. The team now hopes to fine-tune the sensing algorithms and introduce more complex finger configurations, such as twisting.
Chinese scientists develop shape-shifting robot inspired by T-1000 from Terminator, reported in Sep 2020
Chinese scientists say they have developed a type of robot powered by liquid metal inspired by T-1000, the self-repairing, shape-shifting killer android from one of Arnold Schwarzenegger’s Terminator films. They discovered unique properties of liquid metal alloys – high electrical conductivity, controllable surface tension and extreme flexibility that could help with the development of self-reconfiguring robots that can change their own shape.
Li along with Zhang Shiwu from the University of Science and Technology of China, and researchers from the University of Wollongong in Australia made their breakthrough in developing gallium-based liquid metal-powered robots by using voltage changes to trigger movement. Gallium is a soft, silvery material used in electronic circuits and semiconductors. Liquid gallium alloys look like mercury and tends to take the form of a water drop.
They sealed drops of the liquid metal alloy in a tube of solution that changed shape, altering the device’s centre of gravity and turning the wheel, the study said. The process is controlled by changing the voltage of the liquid, and the wheel can be directed to move in a certain direction on a flat surface. “Next step, we plan to use multiple wheels and make it move in a three-dimensional environment,” Tang said.
In the future, we expect to further develop soft robots incorporating liquid metal that could be used in special missions such as searching for and rescuing earthquake victims, since they can change shape to slide under doors or make it through spaces humans can’t get into,” said Tang Shiyang, a research fellow with the University of Wollongong, who was also involved in the study. “Tiny nano-robots could deliver cancer drugs and hunt down tumour cells inside the human body, given its flexibility and high energy conversion rate,” said Li, adding that they could also be used by the military for espionage.
The novel way of rolling wheels could even be put to use by scientists to develop cars that can be run without fossil fuels or electric motor in the future. “Maybe in 10 years, liquid metal robots will be a reality,” Li said.
Robot Octopus Points the Way to Soft Robotics with Eight Wiggly Arms
Cecilia Laschi, professor at the BioRobotics Institute at the Scuola Superiore Sant’Anna, in Pisa, Italy, and her team are investigating soft robots that mimic the form of the octopus. “The octopus has neither an internal nor external skeleton, and its eight arms can bend at any point, elongate and shorten, and stiffen to apply force. It can twist its arms around objects and manipulate them with great dexterity,” she writes. Team has already built robot octopus that could crawl along the seafloor mimicking locomotion of octopus.
The team is creating artificial muscles using materials called shape-memory alloys (SMAs). “When heated, SMAs deform to a predefined shape, which they “remember.” We fashioned SMA wires into springs and ran electric current through them to heat them, causing the springs to scrunch up in a way that imitates muscular contractions.”
“For the Octopus project, my team constructed a prototype arm using SMA springs to stand in for the longitudinal and transverse muscles found in the limbs of a real octopus. By sending current through different sets of springs, we made the underwater arm bend at multiple points, shorten and elongate, even grasp things,” she explains.
“Our work is primarily meant to demonstrate the potential of soft robotics, and much work remains before a robot octopus will be ready to crawl out of the lab.” Harvard researchers have created the first soft octopus robot that is completely self-contained. It is basically a pneumatic tube has no hard electronic components—no batteries or computer chips—and moves without being tethered to a computer.
The octobot is powered by hydrogen peroxide is pumped into two reservoirs inside the middle of the octobot’s body. Pressure pushes the liquid through tubes inside the body, where it eventually hits a line of platinum, catalyzing a reaction that produces a gas. From there, the gas expands and moves through a tiny chip known as a microfluidic controller.
It alternately directs the gas down one half of the octobot’s tentacles at a time which enables octopus to wiggle its tentacles. The octobot can move for about eight minutes on one milliliter of fuel. “You have to make all the parts yourself,” says Ryan Truby, a graduate student in Jennifer Lewis’s lab at Harvard, where the materials half of this research is taking place. The mold for the octopus shape and the microfluidic chip were among the things developed nearby in Robert Woods’s lab.
‘Soft Tactile Logic’ Tech Distributes Decision-Making Throughout Stretchable Material
Conventional machines rely on rigid, centralized electronic components to make decisions, which limits complexity and scaling. Researchers have shown that decision making can be realized on the material-level without relying on semiconductor-based logic. Inspired by the distributed decision making that exists in the arms of an octopus, Researchers developed completely soft, stretchable silicone composite doped with thermochromic pigments and innervated with liquid metal. The ability to deform the liquid metal couples geometric changes to Joule heating, thus enabling tunable thermo-mechanochromic sensing of touch and strain. Using the material itself as the active player in the decision making process offers possibilities for creating entirely soft devices that respond locally to environmental interactions or act as embedded sensors for feedback loops.
Inspired by octopuses, researchers have developed a structure that senses, computes and responds without any centralized processing – creating a device that is not quite a robot and not quite a computer, but has characteristics of both. The new technology holds promise for use in a variety of applications, from soft robotics to prosthetic devices.
“We call this ‘soft tactile logic,’ and have developed a series of prototypes demonstrating its ability to make decisions at the material level – where the sensor is receiving input – rather than relying on a centralized, semiconductor-based logic system,” says Michael Dickey, co-corresponding author of a paper on the work and Alcoa Professor of Chemical and Biomolecular Engineering at North Carolina State University.
“Our approach was inspired by octopuses, which have a centralized brain, but also have significant neuronal structures throughout their arms. This raises the possibility that the arms can ‘make decisions’ based on sensory input, without direct instruction from the brain.”
At the core of the soft tactile logic prototypes is a common structure: pigments that change color at different temperatures, mixed into a soft, stretchable silicone form. That pigmented silicone contains channels that are filled with metal that is liquid at room temperature, effectively creating a squishy wire nervous system.
Pressing or stretching the silicone deforms the liquid metal, which increases its electrical resistance, raising its temperature as current passes through it. The higher temperature triggers color change in the surrounding temperature-sensitive dyes. In other words, the overall structure has a tunable means of sensing touch and strain. Video of the technology can be seen here.
The researchers also developed soft tactile logic prototypes in which this same action – deforming the liquid metal by touch – redistributes electrical energy to other parts of the network, causing material to change colors, activating motors or turning on lights. Touching the silicone in one spot creates a different response than touching in two spots; in this way, the system carries out simple logic in response to touch. “This is a proof of concept that demonstrates a new way of thinking about how we can engineer decision-making into soft materials,” Dickey says.
“There are living organisms that can make decisions without relying on a rigid centralized processor. Mimicking that paradigm, we’ve shown materials-based, distributed logic using entirely soft materials.” The researchers are currently exploring ways to make more complex soft circuits, inspired by the sophisticated sensors and actuators found in biological systems. The paper, “Materials tactile logic via innervated soft thermochromic elastomers,” is published in the journal Nature Communications.
DARPA-backed Soft Robotics raises $23 million for autonomous grippers and sorters
Soft Robotics raised another $23 million to continue developing its solutions to the seemingly intractable problems gripping and sorting machines face. As work published by MIT and others has established, picker robots struggle with complex poses and unfamiliar objects. That’s because they not only have to locate objects and understand how to grasp them, but because they’ve got to set them down such that they don’t sustain damage or disturb their surroundings. Truly versatile picker robots could transform warehouses in industries from ecommerce to manufacturing.
CEO Carl Vause said , Variability is the kryptonite of the robotics industry” . “By offering a system that is able to grasp and manipulate items that vary in size, shape, and weight, we are able to solve the problem of high variability in both products and processes.”
Soft Robotics describes its grippers as a “fundamentally new class” of machine — those that are adaptive, plug and play, repeatable, and reliable. Its mGrip product allows builds with multiple configurations and spacing options with a cycling time of 3-4 times per second and “sub-millimeter” precision, thanks in part to its air-filled soft plastic design. The company’s SuperPick is a robot-agnostic solution comprising a vision system and AI engine that reports real-time metrics, enabling capabilities that include exception handling, remote operator access, object detection, bin localization, grasp detection, grasp quality analysis, and precision placement.
Soft Robotics supplies every component necessary to get its systems up and running, including control units and software that provides control of grip parameters including force, actuator spacing, and opening width. The controller itself can store up to eight grip profiles in total.