This is a hack that combines three of my favorite passions: pacemakers, photography, and coffee!
I took this photograph by feeding the output of an infrared barrier to the atrium input of an old DDD pacemaker, setting an appropriate AV delay, and using the ventricular output to trigger a camera flash (via a optoisolator). In a darkened room, I opened my camera’s shutter for 2 seconds. I then let one drop of milk fall through the infrared barrier, starting the AV delay in VAT mode. The flash then fires as the drop enters the coffee in the cup, freezing the action.
An action sequence is obtained by photographing drops with different delays. The delay can be adjusted by either changing the height of the IR barrier or reprogramming the AV delay.