# Designing circuits

We are engaging the broader community in building and designing these circuits. Every week we will choose several of the top circuit designs and micro-fabricate, build and test those circuits. The winning circuits will be highlighted on the website in the gallery/video section. The goal of the project is to collectively advance the state of the art of the field of "droplet fluidic computing" and explore the vast design space that opens up with the methodology described here.

Here, we describe all the basic design rules which allow you to learn how to design your own "fluidic circuit".

## Design Rules

1. Key building blocks are used to construct all the circuits. Every building block, once designed and optimized will have the exact same desired function and can be reused any number of times.

2. Here we restrict the initial design space to T and I bars; but any number of patterns and basic building blocks will actually work. As the library of designs grow, we will share the same on this website.

3. The blocks can be moved around and placed on a 2D flat sheet. The pattern of permalloy will determine the local time varying energy landscape which the magnetic droplet will follow.

4. Certain scaling laws exist for propagation of a droplet given of a particular size. This size is variable based on other non-dimensional parameters in the problem, such as the size of the bars, frequency of the rotation field and the magnetic field strength. In the current design phase, we will assume an optimal droplet size as being manipulated for a given geometry and only consider droplets of one single size.

5. Every permalloy block should be separated from others by a characteristic length g (or gap length) which is the size of a linear gap between two bars. This is also the distance a droplet moves when hopping from one domain on the bar to another.

## Create your circuit with CAD tools

We recommend two tools for design of circuits. Here we will provide both the test files and step by step instructions of simple circuits to begin with. Note that both are very simple (and fun) to use. You can play with them as much as you want and create crazy circuits. Also, when you submit a circuit, we would prefer that you make it with EAGLE CAD.

## 1) Lego Digital Designer (LDD) - Download here.

This is a perfect CAD tool to start for a beginner. You are probably already familiar with LEGO bricks; the CAD tool allows you to construct any number of LEGO based patterns. Using only a specific type of bricks, you can design with constraints and thus easily implement any possible circuit using the basic building blocks.

Using Lego Digital Designer; and a set of simple rules to constrain the kind of building blocks - fairly complex circuits can be designed very quickly. The video above shows a partial design of a more complex circuit using only two type of key bricks.

Here is the attached .LXF file for the above design.

### Please submit your .LXF files on the link here.

## 2) EAGLE CAD Layout editor - Download here.

This is a more advanced, but also a very simple and freely available CAD tool for making 2D circuits. EAGLE CAD is most often used for PCB design; and we use it here for its simplicity and the possibility to code circuits in an algorithmic manner (repeat modules; vary them in size in a programmed manner etc.)

**Once you have downloaded and installed EAGLE CAD, you should download an example schematic here**.

This file will be your work basis for designing new circuits. In this file, we have already generated the “I” & “T” bars and arranged them in a loop, so you just have to play with EAGLE and pick some basic elements of it (I&T bars, straight line, corners) to build your own circuit.

Open the closed_loop_4x4.sch file and play this video to get familiar with our circuits on EAGLE CAD:

Now, let's get further and learn how to design a logic gate! Before, make sure you have watched the "How an AND/OR gate works" video in the "HOW DOES IT WORK?" section. It will explain you how AND/OR logic gate are represented in our circuits.