Synthetic fibers (rope) that absorb water and shorten

[tarakan]

Hello.

I have an engineering idea, an invention.
I want to make a watering valve for plants that opens the water when the soil moisture content is too low.

I am looking for a material that (1) would not rot, and (2) absorb water and contract at a significant rate to open a valve (millimeter per meter).
I would like to build the device so the same kind of material that would always be wet, inside the body of the valve would create a force that opens the valve.

When the valve opens, the other compartment with the same material would receive water.
Eventually the material in this compartment would become saturated with water and expand, closing the valve.

In the end, this can become a very cheap product that would replace many electronically controlled high pressure watering systems.

I am looking for a fibrous synthetic material that would absorb and hold water, expand with a sufficient enough force to open and shut the valve.

The irrigation system that I am building would use an air compressor powered geyser pump.

There are serious economic reasons for this kind of irrigation system to be used, except for one part - how to keep the plants that are closer to the pump from getting all the water, while the ones that are far away would not get any.

I have a 3D printer so it would not be too difficult for me to design and print the body, build a prototype valve. This is how I built a geyser pump that runs off an aquarium air pump.

At this point I used two ropes of the same length that I tied to a ring, stretched between two nails.
I soaked one rope in the water to see if the ring would move as the rope shrinks. It did not.

I may use coiled rope or felt in my project. I would like to know what polymer fiber material I should use to get the greatest force from expansion when wetted.

Maybe such product already exists. I see a lot of capillary watering stakes, I don't see a valve that opens when soil draws moisture out of synthetic fiber, closes when that fiber gets saturated with water again.

I feel like it is possible.

 

[256bits]

Humidity meters used to use ( and some maybe still do ) hair to control the needle for a meter reading.
https://www.scientificamerican.com/article/bring-science-home-hair-hygrometer/
You could do some experimenting with hair strands, as you look for other suitable materials.

 

[Baluncore]

The mane or tail of a horse will produce the durable and robust hair you need. Horse hair has been used to make hygrometers for well over one hundred years.

If you include a clay and humus in your soil and maintain the right pH, you should be able to water much less often as water storage in the soil will be greatly increased and will be easily available to the roots of plants. Keep the sun and wind off the soil surface.

 

[Tom.G]

Don't know if it is available as a rope,but is available as bulk powder.

https://en.wikipedia.org/wiki/Superabsorbent_polymer

above found with: https://www.google.com/search?source=hp&q=super+absorbent+polymer+used+in+diapers

 

[tarakan]

The super absorbent polymer can retain water, but how easily does it let go of that water?

 

[Tom.G]

Don't know, but one of the article I ran across in the references above mentioned their use in agriculture to reduce the frequency of watering.

All this is far from my area of knowledge, it's just that your inquiry triggered a memory of the stuff. Hopefully there are others here that can contribute some real-world knowledge on the subject.

 

[256bits]

The super absorbent polymer can retain water, but how easily does it let go of that water?

Isn't that an engineering problem that you have to solve. If the material expands as it absorbs water to possible saturation, how will your system be constructed so as dry the material out, if it is within the body of the valve.

 

[tarakan]

I found another solution to this engineering problem.
Thank you for your answers.

The solution is that wet fibers would keep air from flowing through as fast as dry fibers, thus preventing the automatic bell syphon from discharging more water until fibers drie out.

This device is going to be used this Summer in a community garden.

 

[tarakan]

Isn't that an engineering problem that you have to solve. If the material expands as it absorbs water to possible saturation, how will your system be constructed so as dry the material out, if it is within the body of the valve.

That part I already had figured out: material would have been behind the valve - water seeps out - valve opens, valve opens, new water fills the material and it expands and closes the valve.

A new system works on an even better principle as it is very easy to control how much water goes to the soil at every dump.