8. Soft robotics

Research

Soft robotics is an emerging field focused on developing flexible, adaptable robots made from soft materials, such as silicone, gels, and polymers, rather than rigid metals or hard plastics.

These robots are designed to mimic the movement and adaptability of living organisms, allowing them to interact more naturally with their surroundings and handle fragile objects safely.

Soft robotics has applications across many fields, from healthcare and environmental exploration to manufacturing and everyday life.

Key Characteristics of Soft Robotics

1. Flexibility and Adaptability: Soft robots can bend, stretch, and deform, adapting to complex shapes and environments that would be challenging for traditional robots.

2. Lightweight and Safe: Made from soft materials, these robots are often lightweight and pose minimal risk of injury, making them ideal for interacting with humans or handling delicate objects.

3. Biomimicry: Many soft robotic designs are inspired by natural organisms, like octopuses, worms, or the human hand. These designs allow robots to move with high degrees of freedom and to perform tasks that require delicate precision.

4. Air and Fluid Actuation: Soft robots commonly use air or fluid as actuators to create movement. These "pneumatic actuators" inflate and deflate parts of the robot, creating bending or stretching motion.

Applications of Soft Robotics

1. Medical and Surgical Applications: Soft robots are used in minimally invasive surgeries, where their flexibility allows for precise, gentle interaction with organs and tissues. They’re also explored in prosthetics and assistive devices for improved comfort and adaptability.

2. Industrial Applications: In manufacturing and packaging, soft robots are used to handle delicate items, like food or electronics, without damaging them.

3. Exploration and Environmental Monitoring: Soft robots can explore challenging environments, such as deep-sea habitats, where their flexible bodies withstand pressure and complex terrain. They are also used in environmental monitoring to interact gently with plant and animal life.

4. Wearable Robotics: Soft robotics are increasingly used in exoskeletons and wearable devices, providing support for people with limited mobility. These wearables help with physical rehabilitation by providing gentle assistance or resistance during movement.

Challenges in Soft Robotics

• Durability: Soft robots can be vulnerable to wear and tear, punctures, and environmental damage, limiting their lifespan and application.

• Complex Control Systems: Designing effective control systems for soft robotics is challenging due to the complexity of soft material dynamics and nonlinear motion.

• Precision: While soft robots are highly adaptable, achieving precise, repeatable movements is more complex than with rigid robots.

Future Directions

Soft robotics is a rapidly evolving field, with exciting research focusing on biohybrid systems that integrate living cells with synthetic materials, self-healing materials that can repair themselves, and new actuation methods that improve control and durability. The field is paving the way for robots that can seamlessly interact with humans, adapt to unpredictable environments, and open new possibilities for applications in healthcare, wearable technology, and sustainable solutions.

References & Inspiration

Inspirational Projects

• The Octobot: Developed by Harvard University researchers, the Octobot is one of the first fully soft autonomous robots. It draws inspiration from the octopus, using pneumatic circuits and 3D-printed soft materials. It has become iconic in demonstrating the potential for completely flexible robots.

• Festo’s Soft Robotics Projects: Festo, a German automation company, has developed several biomimetic soft robots, like the FlexShapeGripper, inspired by a chameleon’s tongue, and the BionicCobot, modeled after the human arm. These designs are highly innovative and show the potential for industrial and commercial use.

• Wearable Soft Exosuits by Wyss Institute: Harvard’s Wyss Institute has developed soft, flexible exoskeletons that assist with movement and rehabilitation. The use of soft materials allows wearers greater comfort and freedom than traditional rigid exoskeletons.

• Soft Grippers by Soft Robotics Inc.: This company specializes in producing adaptable soft grippers for industrial applications, such as packaging and sorting. Their technology demonstrates how soft robotics can be commercialized effectively for delicate, everyday tasks.

Inspirational Designers and Artists

• Neri Oxman: Known for her work in the field of material ecology, Neri Oxman blends design, biology, and technology to create organic, adaptable structures. Her work with soft, flexible materials and synthetic biology provides exciting possibilities for soft robotics.

• Behnaz Farahi: An architect and designer, Farahi’s work explores the intersection of soft robotics and wearable technology. Her projects, such as Caress of the Gaze, use flexible materials and sensors to create responsive clothing that reacts to a viewer’s gaze.

• Cecilia Laschi: A pioneer in soft robotics research, Laschi’s work has focused on creating robotic systems inspired by marine organisms, emphasizing applications in underwater environments.

Process and workflow

Party horn blower

While engaging with the soft robotics lesson, a vivid childhood memory came to mind: the playful whistles we used to blow at birthday parties and celebrations. These simple yet delightful toys, which unfurled and retracted with each breath, are an early example of soft robotics in action.

It was fascinating to realize that these cherished moments of childhood fun were, in essence, a form of soft robotic mechanism. The concept brought renewed excitement as I reflected on how this playful memory connects to the sophisticated field of soft robotics. Re-experiencing that youthful joy from an analytical perspective enriched my appreciation for the creativity and ingenuity behind these simple yet dynamic devices.

Balloon with vinyl

This week, we dove into hands-on experimentation with creating simple inflatables using vinyl and laser-cut Nofire paper. This method allowed us to explore the fundamentals of air channel design and how strategic planning influences the movement and shape of soft robotic structures.

Materials Needed:

1. Heat press vinyl sheets (two pieces)
2. Baking paper (cut with a laser cutter)
3. Vinyl cutter
4. Heat press machine
5. Air pump or syringe
6. Scissors (optional for refining edges)

Step 1: Design and Cut the Air Channels:

• Start by designing the air channels using Corel DRAW software or vector-based design software (e.g., Adobe Illustrator or Inkscape). The channels should represent where air will flow through the inflatable.

• Cut the air channel pattern out of Nofire paper using a laser cutter. This material will act as a barrier, preventing the vinyl from adhering in certain areas.

Cut the Vinyl Sheets:

• Use a vinyl cutter to cut two identical pieces of vinyl that will serve as the top and bottom layers of the inflatable. Ensure they are slightly larger than your air channel design to allow for sealing around the edges.

Assemble the Layers:

• Lay one piece of vinyl flat on the heat press platform, ensuring it is wrinkle-free.

• Place the laser-cut Nofire paper with the air channel design on top of this vinyl sheet.

• Align the second piece of vinyl over the Nofire paper, creating a sandwich with the vinyl sheets as the outer layers and the Nofire paper as the inner barrier.

Heat Press the Layers:

• Set the heat press to the appropriate temperature and pressure for your vinyl type (typically around 150-160°C).

• Press the layered assembly for 15-20 seconds. This step allows the vinyl to bond only in areas where the Nofire paper is absent, creating the air channels needed for inflation.

• Carefully remove the pressed layers and let them cool for a minute to set.

Test and Inflate:

• Peel off any excess Nofire paper that remains between the vinyl sheets, revealing the air channels.

• Use an air pump or syringe to inject air through an inlet point, inflating the balloon. Observe how the air channels guide the expansion and movement of the structure.
  

This technique provides a quick way to prototype and iterate on different air channel designs, enabling you to understand the relationship between design patterns and movement in soft robotics.

Silicone for Soft Robotics with premade mold

TThis week, our exploration into soft robotics led us to experiment with silicone due to its exceptional properties—flexibility, durability, and moldability into various shapes. Silicone is a preferred material in soft robotics because it mimics organic, natural movements that are crucial for creating lifelike robotic parts.

Step 1: Preparing to Work with Silicone

For this project, we selected Epoxy Master platinum-based silicone 5A for its balanced flexibility and robustness, ideal for creating durable yet pliable components. Additionally, we included Silicone 0A for more elastic elements to achieve a range of movements in our prototypes.

Materials Needed:

1. Epoxy Master platinum-based silicone 5A (Part A and Part B)
2. Silicone 0A
3. Precision scale
4. Mixing container
5. Stirring tool
6. Mold or form for casting
7. Protective gloves
8. Air release agent (optional)
   

Safety Note: Always wear protective gloves and work in a well-ventilated area when handling silicone and other chemicals.

Step 2: Measuring and Mixing Silicone

• Measuring Part A and Part B: Using a precision scale, we accurately measured 32.5 grams of Part A and 32.5 grams of Part B of the Epoxy Master platinum-based silicone. It's crucial to ensure the amounts of Part A and Part B are equal for proper curing.

• Combining the Parts: We poured the measured Part A and Part B into a clean mixing container. The container should be large enough to allow thorough mixing without spilling.

• Mixing Technique: We mixed the two parts slowly and steadily, taking care to minimize the introduction of air bubbles. This step is vital—air bubbles trapped in the silicone can compromise the final piece's flexibility and structural integrity. To mix effectively:

  • Stir using a gentle, folding motion.
  • Scrape the sides and bottom of the container frequently to ensure even distribution.
  • If available, use a vacuum chamber to remove any trapped air bubbles from the mixed silicone.

Step 3: Working with Silicone 0A

To add another level of experimentation, we measured out 60 grams of Silicone 0A, which has a different curing profile and results in a softer, more elastic end product. This provided us with an opportunity to compare properties between the Epoxy Master silicone 5A and Silicone 0A and identify which type better suited specific soft robotic applications.

Mixing the Silicone 0A:

• Follow the same measuring and mixing procedures as with the Epoxy Master silicone.
• Ensure a smooth, uniform mixture, free of any inconsistencies or bubbles.

Step 4: Pouring and Curing

• Pouring the Silicone: Once mixed, we carefully poured both types of silicone into pre-prepared molds. Pour slowly from one spot to allow the silicone to flow evenly and minimize bubbles.

• Curing Time:

  • The Epoxy Master silicone required approximately 3-4 hours to fully cure at room temperature. For faster results, a heat source (such as a curing oven) can be used to reduce curing time.

  • The Silicone 0A typically needed 3-4 hours for full curing but can vary based on ambient temperature and humidity.

• Demolding: After curing, we gently removed the silicone from the molds. At this stage, the silicone should be flexible and show no signs of air bubbles or surface imperfections.

Step 5: Gluing Silicone Parts

• Clean the Surfaces: Before applying adhesive, we cleaned the surfaces of the silicone parts to remove any dust or oils, ensuring maximum adhesion.

• Apply the Adhesive or mixture of resin: Using an applicator, we spread a thin, even layer of silicone adhesive on the edges where the two parts would be joined.

• Join the Parts: Carefully aligned and pressed the parts together to create a seamless connection. Any excess adhesive that seeped out was wiped away to ensure a smooth finish.

• Hold the Parts Together: Clamps or gentle weights were used to hold the pieces in place while the adhesive cured. Depending on the adhesive type, curing times varied from 2 to 6 hours.

• Final Check: Once fully cured, we tested the joint by gently flexing it to confirm it was secure and flexible.

Step 6: Testing Inflation with a Pump or Syringe

1. Attach the Tubing: Connected one end of the tubing to the inlet on the silicone structure and the other end to the pump or syringe.

2. Ensure a Secure Seal: Checked the connection for air-tightness by applying a small amount of air and listening for any leaks. If needed, we applied air-sealant around the tubing connection to ensure no air escaped.

3. Inflate Gradually: Began inflating the structure slowly using the syringe or hand pump. This step was done carefully to monitor the structure’s response and prevent over-inflation, which could cause rupturing.

4. Observe the Movement: As the silicone filled with air, we watched how it expanded and moved. The behavior of the structure indicated its potential applications:

   • If it expanded uniformly and returned to its original shape, it would be suitable for repetitive motion tasks.

   • If it bulged or deformed, adjustments in material thickness or gluing might be needed.

5. Deflation Test: Released the air to observe how well the structure deflated and whether it maintained its original integrity after multiple cycles of inflation and deflation.

Step 7: Results and Observations

Both silicone types produced flexible components, but with notable differences:

• The Epoxy Master 5A yielded structures that were moderately flexible yet maintained a sturdy shape, making it ideal for structural support elements in soft robotics.

• The Silicone 0A demonstrated greater elasticity, suitable for components that needed higher movement capability, such as grippers or actuators.

Using Silicone for Soft Robotics with 3D-Printed Molds

1. Design & Print the Mold: Create a 3D mold with air channels in CAD and print it. Apply mold release if needed.

1. Mix Silicone: Weigh equal parts of silicone A and B (e.g., 32.5g each) and mix for 3-5 minutes, avoiding air bubbles.

2. Pour & Seal: Pour silicone into the mold, tap to release bubbles, and seal with clamps.

3. Cure: Let cure for 3-4 hours at room temperature (or up to 40°C).

4. Demold: Remove cured silicone carefully.

5. Create Inlet: Add a small air inlet if not pre-formed.

6. Test: Inflate with a syringe/pump and check air channel functionality.

Discussion

Safety considerations

CRITERIA	DESCRIPTION	PRECAUTIONS	ACONSEQUENCES OF NEGLIGENCE
Personal Protection	- Gloves: Use nitrile gloves to prevent direct contact, as prolonged exposure may irritate the skin. - Eye Protection: Wear safety goggles to prevent splashes. - Clothing: Protective aprons/clothing to avoid spills.	Always wear personal protective equipment (PPE) when handling Ecoflex™ 00-30.	Skin irritation, eye injury, or clothing damage from spills.
Ventilation	- Work in a well-ventilated area to avoid vapor buildup. - Use masks with filters if working in confined spaces with large quantities.	Ensure proper airflow during mixing and curing.	Possible discomfort from vapor accumulation in poorly ventilated areas.
Mixing and Application	- Maintain a precise 1:1 mixing ratio (by weight). - Follow manufacturer’s instructions for mixing and curing. - Avoid contamination during mixing.	Use accurate weighing equipment and mix thoroughly.	Improper curing, adhesion issues, or degraded performance.
Health Hazards	- Skin Contact: Generally safe, but wash with soap if irritation occurs. - Inhalation: Avoid direct exposure to large amounts of vapor. - Ingestion: If ingested, seek medical help immediately.	Handle with care and wash exposed areas promptly.	Allergic reactions, respiratory irritation, or more severe health issues in case of ingestion.
Storage	- Store in a cool, dry place away from heat and sunlight. - Keep containers sealed to prevent contamination or drying.	Use original, tightly sealed containers.	Material degradation, contamination, or reduced effectiveness.
Disposal	- Dispose of cured material according to local waste regulations. - Do not pour liquid waste down the drain; follow chemical disposal guidelines.	Segregate liquid waste and consult local waste management services.	Environmental contamination or regulatory violations.
Curing Specifics	- Cure at room temperature (4–6 hours) under stable conditions. - Avoid exposing material to extreme cold or heat during curing.	Ensure a consistent environment during curing.	Poor quality or compromised product due to uneven curing or exposure to unsuitable conditions.

Role of Shore Hardness in Silicone Applications:

The Shore hardness of silicones refers to the material's resistance to indentation and provides an indication of its flexibility and rigidity. It’s measured on the Shore A scale, where lower numbers indicate softer, more flexible silicone and higher numbers signify firmer, less flexible material.

• Soft Robotics: Lower Shore A values (e.g., 0A-10A) are preferred for components that need to bend, stretch, or mimic organic movements. These soft silicones are highly flexible, enabling complex movements when air or fluid is pumped into them.

• Molds and Casting: Medium Shore hardness (e.g., 20A-40A) is used for molds that need some flexibility for demolding but also sufficient rigidity to maintain shape.

• Seals and Gaskets: Higher Shore values (e.g., 50A-70A) are ideal for applications requiring durability and less deformation under stress, such as industrial seals and mechanical parts.

Choosing the Right Shore:

• 0A-20A: Highly elastic and stretchy, ideal for delicate, inflatable structures.

• 30A-50A: Moderately flexible with good durability, suitable for more structural yet pliable parts.

• 60A-80A: Firm and resilient, used for parts that need to withstand higher mechanical stress without significant deformation.

Key parameters

Silicon-based soft robotics is influenced by a variety of parameters, which are crucial for determining their performance, flexibility, and functionality. Some of the key parameters affecting silicon soft robotics include:

Material Properties

• Elastic Modulus: The stiffness of the silicon material, which influences how much the material can stretch or compress without breaking.

• Viscoelasticity: The material's ability to resist deformation over time, affecting how the soft robotic structure behaves under stress and strain.

• Tensile Strength: How much force the silicon can withstand before it breaks, which is essential for determining the durability of soft robots.

• Hardness: The resistance of the silicon material to surface indentation, influencing its ability to endure wear and tear.

• Thermal Conductivity: Silicon’s ability to conduct heat can impact the robot's performance in environments with variable temperatures.

Geometry and Design:

• Shape and Size: The overall design of the robot affects its actuation and movement. Complex geometries like wrinkles or folds can enhance flexibility and mimic biological structures.

• Thickness: The thickness of the silicon layer can influence the robot's deformability and strength, affecting how it reacts under pressure.

• Actuator Design: Soft actuators (such as pneumatic or hydraulic systems) made from silicon depend on the material’s ability to deform under applied pressure.

Manufacturing Process:

• Molding and Casting Techniques: Methods like soft lithography, molding, and casting can introduce variations in the material’s microstructure, impacting its mechanical properties.

• Surface Treatment: Processes like plasma treatment or coating can alter the surface roughness, friction, and bonding characteristics of the silicon, which can affect robot movement and interaction with other surfaces.

Pressure and Actuation Mechanisms:

• Inflation Pressure: In pneumatic actuators, the pressure applied to silicon chambers dictates the range of motion and the force generated by the robot.

• Actuator Fluid Type: The fluid used (air, water, or gel) and its properties such as viscosity and compressibility influence the actuation speed and force of silicon-based soft robots.

• Temperature: Temperature can impact the material’s performance by altering its elasticity and deformation characteristics.

Environmental Factors:

• Humidity: Silicon’s properties can change with humidity, potentially affecting its durability and actuation.

• Wear and Tear: Over time, mechanical wear can degrade the silicon's performance, particularly under repetitive motion.

By understanding and manipulating these parameters, silicon soft robotics can be optimized for specific tasks, ranging from medical applications to automation in unstructured environments.

Characteristics of Silicons

CRITERIA	DESCRIPTION	APPLICATIONS	ADVANTAGES	LIMITATIONS
Soft and flexible texture	Exhibits a highly flexible, skin-like texture once cured. It can stretch, compress, or adapt to movements.	Prosthetics, wearable devices, soft robotics	Ensures comfort and adaptability for dynamic projects.	May not provide the rigidity needed for structural applications.
Low Shore hardness (00-30)	Falls in the very soft silicone category, deforming easily and returning to its original shape.	Elastic components, molds for delicate items	Ideal for applications requiring high elasticity and flexibility.	May not withstand heavy mechanical loads or impacts.
Easy to mix and apply	Comes in a 1:1 ratio (by weight or volume) for Parts A and B, with a smooth consistency for pouring into intricate molds.	Complex molds, quick prototyping	Simplifies the preparation process, reducing errors during mixing and pouring.	Mixing errors can result in improper curing or inconsistent material properties.
High abrasion resistance	Withstands wear and tear from repeated use despite its soft nature.	Soft robotics, prosthetics, repeated-use molds	Enhances durability in applications with frequent motion or interaction.	Not suitable for highly abrasive or industrial environments.
Translucent	Allows for visibility into the internal structure of molded pieces. Useful for monitoring embedded components or the curing process.	Embedded electronics, decorative items	Enables visual inspection without disturbing the mold.	May require coloring agents for aesthetic customization.
Low viscosity	Flows easily into molds, capturing fine details and complex geometries.	Detailed jewelry, intricate mold designs	Excellent for projects requiring precision and intricate designs.	May require controlled environments to prevent air bubbles during pouring.
Safe and non-toxic	Non-toxic once cured, meeting safety standards for applications involving direct or indirect contact with skin.	Wearables, medical devices, interactive toys	Safe for extended contact with humans, making it versatile for a range of products.	Requires careful handling during the uncured phase as Part A and B may irritate the skin.
Heat and cold resistant	Performs well across a moderate temperature range but not in extreme conditions.	Temperature-sensitive devices, outdoor applications	Maintains integrity in varying environmental conditions.	Not suitable for extreme heat or chemically harsh conditions.
Curing time	Typically cures in 4-6 hours at 25°C but can be accelerated to 1-2 hours with moderate heat (around 60°C).	Rapid prototyping, time-sensitive production	Flexible curing options allow customization of production timelines.	May require a controlled temperature environment to achieve uniform curing.
Environmental resistance	Resists moisture and general environmental wear, making it suitable for semi-outdoor applications.	Semi-outdoor interactive installations	Prolongs lifespan when exposed to everyday environmental factors.	Not fully resistant to prolonged UV exposure or harsh weather conditions.
Customizable properties	Can be combined with pigments or additives to modify color, texture, or other properties.	Custom prosthetics, artistic applications	Offers a range of customization possibilities to suit aesthetic and functional needs.	Requires knowledge of compatible pigments or additives to avoid compromising material integrity.

3D Models

Soft-robot by fatemmollaie on Sketchfab