Types and designs
Bio-mimicry
Plant cells can inherently produce hydrostatic pressure due to a solute concentration gradient between the cytoplasm and external surroundings (osmotic potential). Further, plants can adjust this concentration through the movement of ions across the cell membrane. This then changes the shape and volume of the plant as it responds to this change in hydrostatic pressure. This pressure derived shape evolution is desirable for soft robotics and can be emulated to create pressure adaptive materials through the use ofManufacturing
Conventional manufacturing techniques, such as subtractive techniques like drilling and milling, are unhelpful when it comes to constructing soft robots as these robots have complex shapes with deformable bodies. Therefore, more advanced manufacturing techniques have been developed. Those include Shape Deposition Manufacturing (SDM), the Smart Composite Microstructure (SCM) process, and 3D multi-material printing. SDM is a type of rapid prototyping whereby deposition and machining occur cyclically. Essentially, one deposits a material, machines it, embeds a desired structure, deposits a support for said structure, and then further machines the product to a final shape that includes the deposited material and the embedded part. Embedded hardware includes circuits, sensors, and actuators, and scientists have successfully embedded controls inside of polymeric materials to create soft robots, such as the Stickybot and the iSprawl. SCM is a process whereby one combines rigid bodies of carbon fiber reinforced polymer (CFRP) with flexible polymer ligaments. The flexible polymer act as joints for the skeleton. With this process, an integrated structure of the CFRP and polymer ligaments is created through the use of laser machining followed by lamination. This SCM process is utilized in the production of mesoscale robots as the polymer connectors serve as low friction alternatives to pin joints. Additive manufacturing processes such as 3D printing can now be used to print a wide range of silicone inks using techniques such as direct ink writing (DIW, also known as Robocasting). This manufacturing route allows for a seamless production of fluidic elastomer actuators with locally defined mechanical properties. It further enables a digital fabrication of pneumatic silicone actuators exhibiting programmable bioinspired architectures and motions. A wide range of fully functional soft robots have been printed using this method including bending, twisting, grabbing and contracting motion. This technique avoids some of the drawbacks of conventional manufacturing routes such as delamination between glued parts. Another additive manufacturing method that produces shape morphing materials whose shape is photosensitive, thermally activated, or water responsive. Essentially, these polymers can automatically change shape upon interaction with water, light, or heat. One such example of a shape morphing material was created through the use of light reactive ink-jet printing onto a polystyrene target. Additionally, shape memory polymers have been rapid prototyped that comprise two different components: a skeleton and a hinge material. Upon printing, the material is heated to a temperature higher than theControl methods and materials
All soft robots require an actuation system to generate reaction forces, to allow for movement and interaction with its environment. Due to the compliant nature of these robots, soft actuation systems must be able to move without the use of rigid materials that would act as the bones in organisms, or the metal frame that is common in rigid robots. For actuation that involves bending, some sort of stress difference must be created across the component, such that the system has a tendency to bend towards a certain shape to relieve this said stress. Nevertheless, several control solutions to soft actuation problem exist and have found its use, each possessing advantages and disadvantages. Some examples of control methods and the appropriate materials are listed below.Electric field
One example is utilization of electrostatic force that can be applied in: * Dielectric Elastomer Actuators (DEAs) that use high-voltageThermal
* Shape memory polymers (SMPs) are smart and reconfigurable materials that serve as an excellent example of thermal actuators that can be used for actuation. These materials will "remember" their original shape and will revert to it upon temperature increase. For example, crosslinked polymers can be strained at temperatures above their glass-transition (Tg) or melting-transition (Tm) and then cooled down. When the temperature is increased again, the strain will be released and materials shape will be changed back to the original. This of course suggests that there is only one irreversible movement, but there have been materials demonstrated to have up to 5 temporary shapes. One of the simplest and best known examples of shape memory polymers is a toy called Shrinky Dinks that is made of pre-stretchedPressure difference
* Pneumatic artificial muscles, another control method used in soft robots, relies on changing the pressure inside a flexible tube. This way it will act as a muscle, contracting and extending, thus applying force to what it's attached to. Through the use of valves, the robot may maintain a given shape using these muscles with no additional energy input. However, this method generally requires an external source of compressed air to function. Proportional Integral Derivative (PID) controller is the most commonly used algorithm for pneumatic muscles. The dynamic response of pneumatic muscles can be modulated by tuning the parameters of the PID controller.Sensors
Sensors are one of the most important component of robots. Without surprise, soft robots ideally use soft sensors. Soft sensors can usually measure deformation, thus inferring about the robot's position or stiffness. Here are a few examples of soft sensors: * Soft stretch sensors * Soft bending sensors * Soft pressure sensors * Soft force sensors These sensors rely on measures of: * Piezoresistivity: ** polymer filled with conductive particles, ** microfluidic pathways (liquid metal, ionic solution), * Piezoelectricity, * Capacitance, * Magnetic fields, * Optical loss, * Acoustic loss. These measurements can be then fed into aUses and applications
Surgical assistance
Soft robots can be implemented in the medical profession, specifically for invasive surgery. Soft robots can be made to assist surgeries due to their shape changing properties. Shape change is important as a soft robot could navigate around different structures in the human body by adjusting its form. This could be accomplished through the use of fluidic actuation. In January 2025, scientists reported having successfully developed a soft robot capable of rapid and powerful joint movements. The new technology can deploy a range of movement from gently stroking an egg, to grab like a hand, crawling across the floor, or jumping high.Exosuits
Soft robots may also be used for the creation of flexible exosuits, for rehabilitation of patients, assisting the elderly, or simply enhancing the user's strength. A team from Harvard created an exosuit using these materials in order to give the advantages of the additional strength provided by an exosuit, without the disadvantages that come with how rigid materials restrict a person's natural movement. The exosuits are metal frameworks fitted with motorized muscles to multiply the wearer's strength. Also called exoskeletons, the robotic suits' metal framework somewhat mirrors the wearer's internal skeletal structure. The suit makes lifted objects feel much lighter, and sometimes even weightless, reducing injuries and improving compliance.Bio-mimicry
An application of bio-mimicry via soft robotics is in ocean or space exploration. In the search for extraterrestrial life, scientists need to know more about extraterrestrial bodies of water, as water is the source of life on Earth. Soft robots could be used to mimic sea creatures that can efficiently maneuver through water. Such a project was attempted by a team at Cornell in 2015 under a grant throughCloaking
Soft robots that look like animals or are otherwise hard to identify could be used for surveillance and a range of other purposes. They could also be used for ecological studies such as amid wildlife. Soft robots could also enable novel artificial camouflage.Robot components
Artificial muscle
Robot skin with tactile perception
=Electronic skin
=Qualitative benefits
Benefits of soft robot designs over fully conventional robot designs may be lighter weight—heavy payloads are expensive to launch—and increased safety—robots may work alongside astronauts.Mechanical considerations in design
Fatigue failure from flexing
Soft robots, particularly those designed to imitate life, often must experience cyclic loading in order to move or do the tasks for which they were designed. For example, in the case of the lamprey- or cuttlefish-like robot described above, motion would require electrolyzing water and igniting gas, causing a rapid expansion to propel the robot forward. This repetitive and explosive expansion and contraction would create an environment of intense cyclic loading on the chosen polymeric material. A robot in a remote underwater location or on a remote planetary body like Europa would be practically impossible to patch up or replace, so care would need to be taken to choose a material and design that minimizes initiation and propagation of fatigue-cracks. In particular, one should choose a material with aBrittle failure when cold
Secondly, because soft robots are made of highly compliant materials, one must consider temperature effects. The yield stress of a material tends to decrease with temperature, and in polymeric materials this effect is even more extreme. At room temperature and higher temperatures, the long chains in many polymers can stretch and slide past each other, preventing the local concentration of stress in one area and making the material ductile. But most polymers undergo a ductile-to-brittle transition temperature below which there is not enough thermal energy for the long chains to respond in that ductile manner, and fracture is much more likely. The tendency of polymeric materials to turn brittle at cooler temperatures is in fact thought to be responsible for theInternational journals
* Soft Robotics (SoRo) * Soft Robotics section of Frontiers in Robotics and AI *Science RoboticsInternational events
* 2018 Robosoft, first IEEE International Conference on Soft Robotics, April 24–28, 2018, Livorno, Italy * 2017 IROS 2017 Workshop on Soft Morphological Design for Haptic Sensation, Interaction and Display, 24 September 2017, Vancouver, BC, Canada * 2016 First Soft Robotics Challenge, April 29–30, Livorno, Italy * 2016 Soft Robotics week, April 25–30, Livorno, Italy * 2015 "Soft Robotics: Actuation, Integration, and Applications – Blending research perspectives for a leap forward in soft robotics technology" at ICRA2015, Seattle WA * 2014 Workshop on Advances on Soft Robotics, 2014 Robotics Science and Systems (RSS) Conference, Berkeley, CA, July 13, 2014 * 2013 International Workshop on Soft Robotics and Morphological Computation, Monte Verità, July 14–19, 2013 * 2012 Summer School on Soft Robotics, Zurich, June 18–22, 2012In popular culture
See also
* Articulated soft robotics * Octobot (robot) * Bio-inspired robotics *External links
References
{{Robotics Robotics Robot kinematics Biorobotics Articles containing video clips