# Fluiduino

A fluidic transistor that I designed and printed.

This blog post is a temperature check for how interested the community would be in an open source, 3d printable, fluidics hardware platform. I want to make sure that this is something that the maker community wants because this isn’t for me, it’s for you. So if you won’t use it, I won’t make it.  First, let me wet your appetite by listing cool projects and applications of fluidics, most of which can be printed on a 3d printer and then I’ll tell you how it works and what I want to do with it.

Awesome projects:

Educational. Teach electronics and logic via the fluid/electric analogy which is extremely strong.

3d printable pneumatic stepper motor made from plastic parts only.

Rocket propulsion control systems.

Steam punk steam robot that can function while on fire.

Robust space travel.

Wood wind magic key piano that opens up a trap door with wind.

Programmable digital computer with no electronics.

Programmable fountain with no electronics that you can interact with.

Microfluidics, biological control. This could be an open source project in its own right.

Smart meta-materials(speculative).

How it works:

The electric/fluid analogy is very strong. Electrons flowing in a wire is much like water flowing in a pipe and in fact, the two systems follow many of the same laws.  A pressure difference is like a voltage, a long narrow tube provides resistance, a membrane is like a capacitor and a coil of pipe is like an inductor. You can send power with electricity and also with fluids(i.e. hydraulic power systems). These are all analog components but the analogy between fluids and electric circuits goes even deeper.  Just like with electric circuits, you can make fluidic circuits digital.  The principle here is that streams of fluid interact with each other. That is, two streams will divert each other, not pass through, so that you can use a control stream of fluid to divert a power stream.  You can use this to build a fluidic amplifier/transistors, logic gates, flip-flops and even a digital computer.

Fluidic amplifier

I’ve taught electronics labs before and let me tell you, electronics are not intuitive to most people. Fluid flow is much more intuitive. One of my main motivations for an open source fluidics project is to make educational kits for high school and college students so that they can gain strong understanding for how electronics work by understanding how the more intuitive fluidic systems work.

Electronics are awesome. I love my computer and I love my Arduino.  But there are some applications that semiconductors are bad for. In particular, you can’t light your laptop on fire and expect it to function. Fluidic computers work just fine when on fire, provided the fluidic device is made of something like ceramics or metals and the fluid is something like gas or oil.  Indeed, you can make your power stream be rocket thrust, very hot, and use a perpendicular small control stream to divert the power stream, thus being able to steer a rocket! Nasa has a nice blurb about his here.

Rocket control

Fluidic rocket control.

Generally fluidics is practical in harsh conditions. Yet another example is space travel.  There are tons of charged particles and other radiation flying around in space that damage semiconductors.  Indeed, semiconductors have to be radiation hardened to withstand these harsh conditions. Because fluidics use fluids instead of electrons for their operation, they can be more reliable in such situations.

Fluidics is just plain cool. The number of steam punk applications are endless. You can make a robot that moves and thinks with steam, just steam! There was someone who made a desk that would play notes via a pipe organ when the drawers were opened. If you open the drawers in the right sequence, a trap door would open. It was made entirely from wood with no electronics. Cool huh?

Fluidic pipe organ desk with a secret compartment

Fluidic pipe organ desk with a secret compartment

One speculative application that’s on the forefront of science that I’m particularly interested in is digital meta-materials.  Digital meta-materials are materials that are made of bits of matter, put together like legos to make something that is functionally more powerful than each individual block.  In this case, I’m imagining fabric with a vascular system that responds to temperature and pressure  via fluidic logic.  I don’t think that 3d printers can beat traditional manufacturing in what traditional manufacturing does well already but I do think that 3d printers can win, hands down, when it comes to complex intricate objects like printing an intricate fluidic vascular system. The philosophy here is that we should be looking for applications of 3d printers that were not possible before.

What I want to do:

I’d like to start an open source fluidics project. Something like Arduino, easy to use, but with fluids. Maybe we could call it the Fluiduino? My primary motivations are educational and inspirations.  I want students to have a deep understanding of electronics and I want makers and hobbyists to easily be able to make rocket control systems, steam robots and programmable fountains. What I want from you is feedback as to whether an open source fluidics platform is something you’d be interested in playing with in the future? I’m not doing this for me, I’m doing this for the community as whole so if you’re not interested, I won’t do it. If however, you feel as inspired as I do, I’d love to find people to work with on this project.

-Sebastian Spiegel

# Printing with Taulman 618 nylon filament

I used my Solidoodle 2, which took three months to get in the mail, 1.5 months longer than was quoted, to print with nylon today and wanted to report on my experience. Fist off, the nylon wouldn’t stick to my print bed. So I clipped paper to the print bed and printed on that. Seemed to stick fine but then kind of warped a lot later in the print and half way came off of the print bed.

Printing nylon with a paper base.

Ventilation. Print with ventilation today and live to print with ventilation another day.  Some websites, and here,claim that within proper temperatures that nylon and ABS is safe. However, when I first received my 3d printer, I printed without ventilation in ABS and had a mighty sore throat and head ache. At home it’s hard for us to know exactly what temperature we’re printing at so to be safe, let’s just assume nylon can emit toxic fumes. I used a duct with a computer fan as well as a large room fan pointed at the window for ventilation and I still wish I had more ventilation. I didn’t smell any fumes but I don’t want to risk it.  In the future I plan to put my Solidoodle in a case and have the duct go completely outside. I could see some smoke come up through the vent which brings me to my next point. I printed at 190 Celsius. I’ve heard rumors that Solidoodle understates it’s temperature and that this is closer to 220 Celsius on other machines. My thermocouple read 180 $\pm 10$ Celsius but then again, half of it was exposed to the air so I’m not sure how accurate that is as well.

As for the print, I heard that nylon is softer than both PLA and ABS, which I can verify it is. It’s not quite elastic like a rubber band, but it does give.  I printed my one way valve with a flap. The flap blocks air in one direction and opens when blown in the opposite direction. A soft plastic makes a better seal, thus this is a perfect test item for my nylon filament.  You can download and print it here. The nylon had some oozing which made the flap stick to the wall. I had to cut this away with a knife. But once I did, the valve worked like a charm, blocking 80-90% of the fluid flow in the reverse direction.  I can’t wait to try this print out on elastic ABS and soft PLA!

Valve with a flap

Valve with a flap

# Fluidic logic

I recently made a blog post about the analogy between fluid flow in pipes and analog electric circuits.  Of course, I’m not the first to think of this. It’s called the hydraulic analogy.  But it’s not just analog circuits for which this analogy carries over, the analogy works for digital electronics as well. That is you, can do logic gates hydraulically. This is called fluidics and there already happens to be designs for how to construct hydraulic amplifiers. With hydraulic amplifiers, you can do logical operations.

How does it work? A very small stream of fluid deflects a very large stream. First I’ll show you how to do a NOT gate, then an AND gate and together NAND.

NOT gate:Simply take the left outgoing tube as your output. Done.

AND gate:To do an AND gate, take the output of the first amplifier, the right side, and feed it into the large stream of the second amplifier. Now the second amplifier will only have a stream in the right hand side if both control streams are on. BOOM! An AND gate.

Together, you can make a NAND gate and NAND is universal for logic which basically means you can make a computer if you can make a NAND gate.

The RepRap project was how I first learned about 3d printing. It has the remarkable mission, in that I’m remarking about it, of printing all of the parts to make another printer. Wow. Well, in principle, all of the circuits can be replaced with pneumatic ones. And also, you know, it might make a cool theme for a sci-fi flick. Just imagine a 3d printer printing with a background of hydraulic valves, pumps and hoses. Generate a pressure difference with steam and you’ve made a steam punk wet dream.

Now I’m not suggesting that we start running our 3d printers this way. The point is, if push came to shove, 3d printers could print out much more of their parts than they currently do without the need to resort to printing new materials.

In honor of the RepRap project, I designed a printable version of the fluidic amplifier. You can find it on thingiverse here. You can test that it works using your mouth.

Instructions:Just print it out twice and hold it together, tape it together, screw them together or glue them together. Doesn’t matter how you do it. Just make sure they stay together. To test them, you only need to hold them together with your hands and blow through the power port and one of the output ports. I just tested it and between 70-90% of the air went through the right output port. Considering that I was holding them together with my hands and using my mouth, that’s pretty freakin’ good. 🙂

I should also point out that this thing was already patented in 1974.

# Tesla valve:print in one piece

Tesla valve is a one way valve with no moving parts that gives a preferential direction of air/liquid flow.  It’s exciting because most one way valves have a flap that closes are a ball that blocks flow in a particular direction.  But not the Tesla valve. It uses air itself to block air from passing.

Today I decided that I wanted to print a Tesla valve but all the designs I’ve seen require you to print it in two parts and then use screws to hold it together. That seems like too much work so I decided to design a Tesla valve that prints all in one piece.  You can download it here. This is all part of a bigger project which I plan to unveil in the future 😉

My first design was  kind of wonky. Blowing in one direction you would get smooth air flow and in the other, turbulent air flow but still quite a bit of flow.  added the fins in as well but the airflow is still substantial. I guess I’ll have to get back to it some other time.

Here’s my printer printing this Tesla valve:

# 3 improvements that could be made to 3d printers

Oh, how I wish I had more than one life to live. Then I would have the time to do all the things that I want to instead of just talking about them.

Most recently, right now, I came up with a few wishlist items that would improve additive 3d printers tremendously.  For all I know someone is already doing these things or maybe YOU, the reader already are. In which case, please let me know because that would be pretty cool. If enough time goes by, I might even attempt to do these three things myself. Without further ado, here they are:

1. Use 5 axes rather than 3 axes.

Support material sucks.  I mean, it’s great because it allows you to build up complex structures, but it’s expensive and it leaves marks when you break it away. If you could rotate the work piece, you could always be adding on top instead of from the side.  Certainly some support material might still be needed in cases where the printer head simply does not fit, but being able to rotate the work piece would certainly reduce the amount of support material.

2. Use feedback via a camera or laser to detect errors.

3d printers are rather dumb right now. If it screws up, it just keeps on going and going and going until you come back from having your tea and realize that you have gobbly goop left.  Wouldn’t it be nice if your 3d printer actively scanned your work piece and compared it to your 3d model?

3. A router bit to correct errors.

Given that you can detect errors from point 2, why not correct them? A rotary cutter would allow you to remove mistakes and smoothen the work piece. You might need a vacuum system to go with this so that scraps don’t get in the way.

If any of my readers know of an example of these three things being done or ever do these things, please please let me know so that I can tell you how cool you are.

-Sebastian Spiegel