[From the last episode: MEMS technology has been critical for enabling micro-scale sensorsA device that can measure something about its environment. Examples are movement, light, color, moisture, pressure, and many more. and actuatorsA way of controlling some device electronically. It might turn the device on or off or change a setting or property or do any other thing that the device is capable of..]

A first warning: this post and the next one may tax your imagination. So buckle up!

We’ve seen the basic processing steps needed to make things on siliconAn element (number 14 in the periodic table) that can be a semiconductor, making it the material of preference for circuits and micro-mechanical devices.: deposition, etching, and litho. When these are the only things you can do, it changes how you build stuff. While building circuits has little in the way of a real-world analogy for everyday folks, building mechanical devices has direct equivalents. By looking at one – digging out a backyard swimming pool – we can see how differently we would do things if those three steps were all we had.

The Normal Way to Build a Pool

First, full disclosure: I’m not a contractor. So hopefully any of you that are contractors will cut me some slack. I’m going to describe how I would envision digging out a pool using traditional tools. No diving board, nothing fancy. Just a concrete-lined pool.

Here are the rough steps we would take:

1. Get a backhoe and dig a hole for the pool.
2. Smooth it out.
3. Apply concrete/plaster to the sides and bottom of the pool to line it.

This ignores, of course, hardscaping around the pool, decorative elements, stairs, and other details. Analogies are great that way; we can get away with things that a real contractor could never get away with!

The Philosophy of a MEMS Approach

Let’s look at the MEMS side of things first just conceptually; we’ll do detailed steps in the next post. One of our main limitations is that our setup has to be what’s called planar. That means everything has to happen in a flat layer, in a single plane. That’s a huge deal.

Another important consideration is that pretty much everything we do will affect the entire backyard. We can’t just do something to one spot; if we want to do that, we have to use litho* to isolate that spot and protect the rest of the yard before we can do anything. Obviously, when we dig the pool, we’ll need this – or else we’ll dig out the entire backyard.

The basic steps we’ll need are:

1. Figure out how to dig a hole only in the pool area.
2. Line the pool with concrete. But concrete will end up everywhere, and it’s hard to remove. So we need to think about how we’re going to do this. In the next post, there are a lot of steps required to accommodate this.
3. We need to remove everything around the pool when we’re all done so that all we’re left with is a concrete-lined pool where we want it and bare dirt everywhere else.

The result will be a process way more complicated than we need when using the normal tools for our macro world. I’ll detail those in the next post; I’m separating them so that you get a break in between them – or else it would be one long bizarro post.

So… up next is a detailed recipe for building a pool. Yeah… I’m thinking that, if you have a pool in your future, you’ll opt for the normal approach.

 

* There’s no true litho in the sense of using light to expose a pattern. But we will use a maskA piece of glass with a pattern on it that is used to block light or let light pass through in different places. Used for photolithography., so that’s what I’ll call litho here.