For our second BioPrinter platform, we intend to build an XY stage from a couple of CD drives, inspired by this DIY laser cutter / microfluidics platform by Hackteria:

http://hackteria.org/wiki/index.php/HackteriaLab_2011_Commons#Micro_Manipulator

http://hackteria.org/wiki/index.php/DIY_Micro_Dispensing_and_Bio_Printing

http://hackteria.org/wiki/index.php/DIY_Micro_Laser_Cutter

http://hackteria.org/wiki/index.php/DIY_Microfluidics#Advanced_DIY_Microfluidics

http://hackteria.org/?p=1186

Here's where they got their inspiration from:

http://builders.reprap.org/2010/08/selective-laser-sintering-part-8.html

Here's some other versions, via Hackaday:

CNC machine from PC parts

Build a mini cnc machine for $45

Blu-ray CNC looks great for branding and engraving

Laser CNC from Bluray parts

Bluray Laser CNC – version 0.2

So far, Cameron brought in five CD drives from TechShop, and we've started disassembling them. Unfortunately, it looks like the three identical drives we have may be using DC motors to move the read head. Not sure that will work for our needs. More drives to disassemble...

We pulled the drives apart, extracted the stepper motors and rails to control each axis.

Model #PL15S020 BIPOLAR (2 directions)

Data sheet:  http://robocup.idi.ntnu.no/wiki/images/c/c6/PL15S020.pdf

Option for hardware interface if not arduino: http://robocup.idi.ntnu.no/wiki/index.php/Controlling_stepper-motors

(Note that these guys use a Cerebot microcontroller, based on an Atmel ATMega64 processor, and an H-bridge module from Digilent based on the same SN754410 chip we ordered.) 

The Arduino.cc website has some Circuits for Bipolar Stepper Motors

We ordered five SN754410NE H-Bridges to implement the second circuit