Effect of acetone vapor on thermal printer paper

I am not sure of the chemistry involved, but I have found that acetone and isopropanol vapor will darken the ink in thermal printer paper. There is also a strange reversible blanking effect, where continued vapor application will cause the dye to temporarily become colorless. Do you know the chemistry involved?

High resolution picture of remote focus control box

By request...

Water vortex display from SJ City Hall exhibition -- repair and upgrade

I built this project a few years ago with a friend to help get him interested in mechanical design. Later, the project was adapted for display at a "tech and art" exhibition at San Jose City Hall. After 8 months, the painted steel impeller began to rust and discolor the water in the tube. I took the device back to my shop and replaced the original aluminum shaft with a stainless steel shaft, replaced the shaft seal, and changed the impeller to an all-plastic design. If I were designing the device again, I would opt for a spring-loaded PTFE (Teflon) shaft seal, which I have used with great success in other applications.

Drill motor control:
http://www.youtube.com/watch?v=7yEABsNyRfo

Original video showing the WiFi-controlled watering can and vortex tube:
http://www.youtube.com/watch?v=XKrlRJ-GJms

Repairing the 5V output from a Mastech HY3005D-3 (cheap import) power supply

The 5V fixed output on my Shenzhen Mastech HY3005D-3 power supply died the other day, and so I took the device apart to investigate. The 5V regulator board had a bad solder joint where the bridge rectifier attaches to the PCB. I used a soldering gun to reflow the joints, and all seems good.

Transcranial Magnetic Stimulation project - part 2

I achieved neuronal stimulation of my primary motor cortex by using a single 15-turn coil and 1700 volt charge on the capacitor bank of about 190uF. The exact position of the coil on my scalp makes a very big difference in how much stimulation is achieved in the motor cortex. I would have suspected the single coil would produce much more diffuse stimulation and positioning would not be so critical. I never got any decent neuronal stimulation with the butterfly coil.