Simsim Pendant

5 Mar 2024
Progress: Concept

It may come as no surprise that one of the projects I'm working on lately is attempting to create a realtime fluid simulation on embedded hardware. There are many applications, from volumetric virtual candles to interesting jewellery and trinkets.

Running a mixed liquid/air simulation is somewhat more complex than a fire simulation, but there's an irrefutable appeal to having a physical item in your hand, displaying a virtual glowing liquid, that sloshes around as you tilt the contraption. Stay tuned for that.

But while discussing methods of chasing this goal, the concept of "faking it" arose – that is, to simulate the simulation, using a real liquid.

Consider a grid of LEDs arranged on a PCB. Instead of a matrix, all the LEDs are wired up to a single power rail. The other connection for each LED is on the underside of the PCB. For each pad, if it's shorted to ground, the LED above it will light up.

We then mount this PCB a small distance away from a glass panel, seal the edges, and partially fill the gap with mercury.

In essence, what we're building is one big mercury tilt switch.

The liquid metal forms the other power connection, and so as it moves around in the sealed chamber, the LEDs above it would light up accordingly.

It doesn't have to be mercury, of course, there are other alloys available which are less toxic. A mixture of gallium, indium and tin is liquid at room temperature. Depending on the exact ratio, different melting points are achievable. I quite like the idea of a pendant filled with liquid metal that only comes "alive" while it's being worn: the heat of your body keeps it liquid. When you take it off, the liquid freezes and the magic disappears.

From the front, the device would appear to be running a fluid simulation. From the rear, the truth of liquid metal becomes clear.

We are presenting a digital render of the device, which makes this a fluid simulation simulation simulation.

Gosh this would be fun to play with.

All right – sold – maybe I will build it at some point.