How to make soft and squishy robots

For the majority who stand outside the robotics sector, our perceptions of robots are often inspired from science fiction narratives and cinematic portrayals — by the likes of Isaac Asimov with his visionary laws of robotics, to the iconic duo C3PO and R2D2, among countless others. Our collective imagination once painted robots in the anthropomorphic image, mirroring human form. However, today’s reality diverges significantly. Modern robots are specialised industrial tools, designed for precise tasks — be it a singular robotic limb or a complex assembly of mechanical armature and sensory equipment. The so-called humanoid robots of our era merely echo the basic human structure, equipped with a head, torso, limbs, and rudimentary sensory inputs akin to sight and sound.

But what about true human-like?

The major challenge to robots becoming more human-like is the skin and the sense of touch, and responses to it. The complexity of design in creating human-like skin for robots is enormous: considerations of texture, elasticity, and sensory capabilities — the physics of touch — is a challenge of balance between real and artificial.

Integrating human-like skin into robots can also be a software challenge, not just a hardware challenge. The human skin is a sensitive organ capable of detecting a wide range of tactile stimuli with precision. Replicating this level of sensory accuracy including pressure, temperature and texture can be challenging to integrate into robotic systems because of constraints around compatibility, space, and power requirements.

What the challenges with hardware and software mean to creating human-like robots is high-cost and low-scalability, as well as concerns of maintenance, hygiene, and durability.

But, a new research, from a team led by Kyungseo Park and Kazuki Shin, on “Low-Cost and Easy-to-Build Soft Robotic Skin for Safe and Contact-Rich Human–Robot Collaboration” has presented a novel solution — an easy-to-build soft robotic skin that could revolutionise how robots perceive and respond to human touch.

The groundbreaking paper from the IEEE Transactions on Robotics shows methods to employ air-pressure sensors and 3D-printed pads to provide a level of sensitivity and safety previously unattainable at a low cost.

The implications for industries like healthcare, personal robotics and any industries where robots and humans interact in a social setting are profound, potentially leading to robots that are not only safer but also more capable of complex social interactions with humans.

Why Soft Robotic Skin?

Traditional robots operate in structured environments where interactions with humans are minimal. However, as robots move into roles that require more direct contact with people — such as in homes, hospitals, or workplaces — the risk of accidental injuries increases. Hard exteriors can cause harm upon collision, making the integration of soft, sensitive materials essential for safety.

Giving robots a lifelike appearance and texture with the use of soft skin creates a more approachable and engaging presence. Imagine a robot that not only performs tasks efficiently but also looks and feels like a friendly companion, making the human feel more comfortable at vulnerable times.

The newly developed soft robotic skin addresses these concerns. It covers a robot’s hard surfaces with a layer that can sense pressure changes caused by physical contact. This skin is not only shock-absorbing but also capable of detecting and interpreting various types of touch, from gentle pats to firm presses. The technology is based on a network of air-filled pads made from thermoplastic urethane (TPU), a material chosen for its durability and flexibility.

One of the standout features of this technology is its simplicity and affordability. The skin can be produced using standard 3D printers and off-the-shelf sensors, making it accessible to a wide range of users—from industrial designers to academic researchers and hobbyists.

Each pad in the skin functions as an independent sensor, measuring changes in internal air pressure when deformed by contact. This data is then processed to distinguish between different types of interactions, like a steady push or a quick tap. These sensors are integrated into a system that utilizes the Robot Operating System (ROS), allowing for easy adoption and integration with existing robotic systems.

Is it good enough?

The research team demonstrated the effectiveness of their design with a custom robot equipped with the soft robotic skin. The robot could safely interact with humans in a controlled environment, responding to touch by adjusting its movements to avoid potential harm. This capability was showcased in scenarios where the robot had to navigate around human operators, adjusting its path in real-time to prevent collisions.

In addition to safety, the soft skin enhances a robot’s ability to perform tasks that require delicate handling, such as in assembly lines or when interacting with the elderly in caregiving scenarios.

While the current design offers significant improvements in safety and tactile response, the team acknowledges that further enhancements are needed. Future versions could feature improved spatial resolution, allowing for even finer distinctions between different types of touch. Additionally, integrating sensors that can detect temperature or texture could further enhance a robot’s perceptual capabilities.