Traditional Robots Versus Soft Robots
When we think about robots, we usually imagine smart and sophisticated machines in different forms that are made of connected metal or plastic parts which their sole purpose is to perform repetitive tasks in isolated environments such as factories. Such traditional robots are not safe to interact with humans since they are made of rigid materials. For them to be safe they require various sensors along with complex algorithms that enable them to sense their environment and consequently detect the presence of humans or objects in proximity.
Let us consider the following scenario. Suppose that we want to fry an egg in the morning for breakfast. To pick up the egg from the fridge safely using our hands without breaking it our brain uses our eyes as sensors to decide that this is an egg and it requires a gentle touch. The visual data collected using our eyes is used along with past learning experiences by the brain to make such a decision. Artificial intelligence in machines is quite similar to the learning experience of the human brain. Now, let us suppose that the challenge is to pick up the egg while we are blindfolded. Our brain will decide whether the object is an egg or not and how to handle it by relying on our touch sensation and past learning experiences by interpreting its texture and shape. This is another form of sensation known as tactile sensation.
To make robots smarter just like humans we need to equip them with similar sensors. Now, let us suppose that we want a traditional robotic hand that is made of rigid parts to pick up the egg. The challenge is to build a robotic hand similar to our hand in terms of functionality. This means that various sensors are required in the structure of the robotic hand in addition to complex algorithms to inform it about the position of the egg and that this is a delicate object that requires a certain grasping force to hold it successfully without crushing it.
But in this scenario, we are trying to pick up an egg. What happens if we need to pick up a ripen tomato instead which has a different shape, size, texture, weight, and stiffness? The short answer is that we need to reprogram the robotic hand to handle it safely without squashing it because the environment has changed.
For now, picking a simple object using a traditional robotic rigid hand seems to be a very challenging and demanding task.
Fortunately, soft robots that are made of soft and deformable materials can accomplish this simple task easily. Due to their inherent softness, soft robots can bend, twist, elongate, and contract. This means that they can adapt themselves to the shape of the objects being handled and therefore dramatically reducing the contact forces between their structure and the objects by increasing the contact area.
Let us consider the following example to understand this point and the importance of soft materials in robots. Imagine that we have two identical small balls in terms of the size where one is made of steel and the other is made of rubber. If we hit both balls against a wall, we know that the steel ball can easily damage the wall while the rubbery one will bounce back without leaving any damaging marks on the wall. Here, the softness of the rubbery ball prevented it from damaging the wall by deforming upon hitting it and therefore distributing the forces over a larger area and absorbing the energy of the impact.
Hence, a single soft robotic hand that is made of soft and deformable materials can be directly used to safely pick and place diverse objects with different shapes, sizes, textures, weights, and stiffnesses without requiring any of the sensors or algorithms required by traditional robotic hands since it can passively adapt itself to the shape of the objects being handled.
This means that soft robots are ideal to operate alongside humans in dynamic environments and to manipulate and interact with delicate objects.
The soft robotics field takes inspiration from nature. Animals such as octopuses, muscular organs such as the human tongue, and plants such tendrils are examples of entirely soft bodies found in nature.
Advantages of Soft Robots
The rapid growth of the soft robotics field is driven by the distinct advantages that soft robots offer as compared to traditional rigid robots. First, soft robots are made of highly deformable materials, which make them ideal for interacting safely with humans and dynamic environments. Second, soft robots can be made of biocompatible passive and smart materials with different properties, ranging from ultra-soft materials to compliant ones, which make them safe to be used directly on the human skin and inside the human body in some cases. Third, the soft materials and the methods for making soft robots, such as 3D printing are cost-effective, making them very accessible and affordable, and allowing their complete fabrication so that minimal or no assembly processes are required. Finally, the softness of soft robots makes them ideal for handling extreme external mechanical deformations without any damage and for manipulating delicate objects without damaging them.
3D Printing Empowers Soft Robots
The most common way to develop soft and deformable robots is by molding silicone using carefully designed plastic molds. The molds can be designed to produce soft robots with various shapes. However, this fabrication technique limits the development of scalable soft robots with complex shapes. Additive manufacturing commonly known as 3D printing is a highly desired fabrication technique for developing soft robots. 3D printing offers many advantages for developing soft robots. First, complex geometries can be considered to design soft robotic systems. Second, various designs can be manufactured rapidly without requiring laborious manufacturing steps and lengthy assembly processes. Third, various passive and smart materials with different mechanical properties can be used to 3D print soft devices. Finally, soft robots can be easily scaled and customized to be tailored to specific applications.
Challenges of Soft Robotics
The aim is to have untethered soft robots that are made completely of soft materials. This means that the structures, driving mechanisms, electronics, and power sources of a soft robot must be soft, deformable, or stretchable. However, this is still a challenge for scientists and engineers. Intensive research is being conducted to develop entirely soft robots.
Although soft robots are safe and ideal to interact with human and delicate objects, sometimes their softness stands as a limitation. Because they are soft, they cannot produce or exert large forces as traditional robots. This why soft robots are not here to replace hard robots but to address some of the engineering challenges that face traditional robots. Thus, it is desired that we have robots that can switch quickly between two different states of soft and hard gradually or discretely on demand just like our fingers.
Applications of Soft Robotics
Soft robotic systems can be in diverse forms including soft robotic hands and soft grippers for dexterous and safe manipulation, locomotion robots such as humanoid and underwater robots for exploring dynamic environments, artificial muscles for movements and force generation, human-machine interfaces, wearable soft devices such as soft exoskeletons for human performance augmentation, rehabilitation devices that can be custom made to target specific needs, extremely small soft robots that can navigate narrow areas in the human body and many other interesting applications.
The Future of Soft Robots
The soft robotics field is an exciting field that is changing the way we think, make, interact, and perceive robots. Soon robots will live among us and they will look a lot like us thanks to the soft robotics field which allows us to build soft, smart, and safe robots.