making.do

An eclectic collection of projects

Paramecium/Arduino interface

Control paramecia with your mind! Watch as hundreds of unicellular organisms respond to my mental command, with the help of about $50 worth of parts:

This project was developed as a demonstration for a course I taught at Genspace, the Brooklyn-based open bio lab/biohacker space.

How it works

Paramecia display a behaviour known as galvanotaxis: movement in respons to an electrical field. If an electrical field is generated across the water they are swimming in, they will turn to orient themselves to the field and will swim towards the anode cathode (negative terminal).

The mind control mechanism takes advantage of this: I developed a laser cut stand with a small (14mm x 14mm) well in it to hold paramecia. By placing electrodes (pencil leads) on each of the four sides of the well and attaching them to four I/O pins on an Arduino, I can use the Arduino directlhy to send 5V at a few tens of mA through any pair of electrodes. This establishes a field of about 3.6 V/cm, which is right in the sweet spot of the field strength that paramecia respond to.

The brain sensor is from a kids’ toy which contains a Neurosky EEG processing ASIC. This measures basic brain wave activity and also generates a composite ‘attention’ measure which supposedly measures your degree of concentration and focus. Exactly what is being measured there is a subject of some debate, but with a bit of practice it’s possible to train yourself to enter the right ‘attention’ state to increase this value.

I hacked the brain sensor to send its output to an Arduino, and used a simple piece of code to trigger a current across the electrodes when my concentration exceeds a given threshold. So, I can literally will the paramecia to move up the screen, and when my will is strong enough, up they go. At the moment, this works in only one direction (I’ve chosen ‘up’), but with a more sophisticated sensor (e.g. the Emotiv headset), it should be possible to distinguish multiple states and steer your microscopic minions any way you like.

I use a (minimally) hacked webcam to act as a basic microscope to allow me to display the paramecia on my computer. Using really basic image processing code written using the OpenCV library, I can track the paramecia in software, opening up all sorts of interesting interaction possibilities.

Build your own

All the details you need to do this at home are here, including a list of parts and sources, build instructions, and a downloadable archive with plans for the laser cut stand and example Arduino code to get you going.

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