Pneumatic structures

“If a pressure difference occurs separated by a membrane, i.e., a flexible foil, easy to bend, and with comparable high tensile strength, the membrane buckles to the side of the lower pressure and is stabilized laminary. The result is a single-curved or double-curved surface, shaped by the pressure difference and the cutting of the foil.” (Hartz et al., 2010). 

To simplify this we can say that Pneumatic structures are constructions that use air or gases to create their shape and support. They typically consist of a flexible, inflatable membrane filled with air. These structures are lightweight and easy to assemble, and their stability relies on maintaining the right air pressure inside.

Let me show you some examples of pneumatic structures in:

- Living organisms.

- structural engineering.

- Soft Robotics.

Pneumatic structures for movement in living organisms

Buoyancy control:

It is an object or organism's ability to adjust its position or depth in a fluid to achieve a desired level of buoyancy. It can be achieved through various mechanisms, depending on the object or organism.

For Example Swim bladders in fish: 

Swim bladders are gas-filled organs found in many bony fish that play a crucial role in buoyancy control, allowing the fish to regulate their position in the water column. The swim bladder is essentially a flexible-walled sac filled with gas, primarily oxygen or nitrogen. Its key function is to adjust the overall buoyancy of the fish by controlling the volume of gas within the bladder.

Siphuncle in cephalopods:

It is a tube-like structure that runs through the chambers of their shell. The siphuncle is used to control the gas content in these chambers, allowing the animal to adjust its buoyancy and stay afloat at different depths in the ocean. It connects to a gas gland within the animal's body, which produces and removes gas as needed. The gas used is typically nitrogen. The gas gland can add gas to the chambers, increasing buoyancy, or removing gas to reduce buoyancy.

pneumatic structures for motion in Snakes:

Snake locomotion primarily relies on the contraction and relaxation of muscles, along with manipulating their bodies to move effectively. However, snakes do have a specialized respiratory system that involves air sacs located along their body, which allows for the elongation and compression of their body during movement. which play a role in their movement and overall physiology.

These air sacs serve multiple functions:

1. Respiration.

2. Efficient Movement: The presence of air sacs in snakes contributes to their flexibility and agility. By adjusting the volume of air in these sacs, snakes can stretch and contract their bodies, allowing them to move smoothly over various terrains, climb, and squeeze into tight spaces.

Pneumatic structures in structural engineering

Air-inflated structures:

the air pressure is applied between the surface and the ground. 

Air-inflated structures work by utilizing a flexible membrane, often made of reinforced fabric, that is inflated with pressurized air. The introduced air creates internal pressure, providing structural support and shaping the three-dimensional form of the structure. The controlled pressure inside the membrane ensures stability, while the lightweight nature of the materials allows for portability and adaptability. This innovative approach offers a versatile solution for temporary or semi-permanent enclosures in architectural and engineering applications.

Air-supported structures:

the air pressure is enclosed in a cushion or a tube. 

Air-supported structures work by maintaining a constant internal air pressure within a flexible, airtight membrane. This positive pressure supports the structure, creating a stable, enclosed space. The lightweight and adaptable nature of these structures allows for quick assembly and versatile applications in areas like sports domes and temporary shelters.

Pneumatic Structures in Soft Robotics

Soft robotics use inflatable structures to move gently and adapt to different tasks. These robots operate by controlling air pressure to achieve flexible and versatile movements, making them suitable for delicate tasks or navigating complex environments.

Pneumatic Forms

After we Learned the meaning of Pneumatic structures and shapes and how they work, We started exploring and experimenting with pneumatic shapes using “plaster” and “Balloons”, and here comes the real fun. Let me walk you step by step through the process.

Required Equipments:

All we needed for this experiment were:

- Plaster.

- Water.

- A bucket.

- A stick to stir the plaster with.

- Balloons.

- Water Guns.

- Your own hands or any other thing you find useful.

P.S. Plaster used in molds, often called plaster of Paris, is a white powder made from gypsum. When mixed with water, it forms a paste that can be poured into molds. It hardens quickly to create detailed casts

The process:

1. Fill the bucket with water.

2. Start adding the plaster powder until it makes a mountain above the water.

3. Start stirring the mix slowly.

4. Start filling your water gun with the plaster.

5. pour plaster into a balloon.

6. Clean the outside of the balloon, then close it.

7. Start shaping it either with your hands or using anything. It takes around 10 minutes to dry.

8. Peel off the balloon and voila, your shape is ready.

 P.S. If you stir fast, the mix will have air bubbles, and it will appear in your shape. (Found out the hard way).

Final Outcome

While working and experimenting with shapes each one of us tried to use a certain concept or approach. Some of use used cylindrical shapes to form their shapes others used pointy stuff. My approach was to use my hands and twist. I was surprised by how many different shapes I could come out with by just using one technique.

Inflatable Pneumatic Forms

The next step is more practical or technical if I may say. We were asked to Design 3D Molds to create shapes out of silicon that can be inflated and create different forms.

First, we have to decide on the shape we want, Then we start building the Mold on 3D software. 

For the first of my shapes, I was trying to imitate the use of a finger and try to apply more than one piece to achieve different functions. such as crawling or picking things up.

For my second shape, I tried to mimic the Siphuncle in cephalopods. it will have no function just an experiment to see how shapes can change when inflated with air according to their air chamber structure.

Then we send the 3D models to be 3D printed, then when we get the physical mold we start preparing the Silicon mix and pour it into the mold.

We start mixing the silicon by adding 1:1 from the A and B containers, Then we start stirring them slowly to get rid of the bubbles. We might use an air vacuum chamber to get rid of all the air bubbles but this speeds up the drying of the silicon. 

After we are done mixing we start pouring the silicon into the molds.

ahhh but first we should add wax to the molds to make it easier to extract the silicon from the mold.

The silicon takes between 3 to 7 hours to dry depending on the type of the silicon.

When the silicon dry we start taking it out of the mold. We have two parts, the base and the main body. We start gluing them together also using silicon.

After we glue the base and the main body together and the silicon dries, now we can test our shapes to see how they will look after inflating them. 

In my first shape, I kind of expected in my mind how it would work. and luckily it worked as expected let me show you.

For my second shape, I didn't have any expectations I wanted to experiment with it.

Let me show you also.

Summary

In conclusion, my experience in the pneumatic form-finding class has been both refreshing and liberating. This unconventional approach allowed me to break free from traditional design constraints, emphasizing form exploration over functionality or rationales. It sparked a newfound creativity, encouraging me to step outside my comfort zone and experiment boldly. Working hands-on with pneumatic structures was not only enjoyable but also a valuable reminder of the importance of embracing unconventional methods in the pursuit of innovative design.