Jamie Matthews' 3D-Printable Flashlight is Ready for Emergencies — Just Add Water

Maker Jamie Matthews has designed a 3D-printable flashlight that rather than using traditional batteries, it turns magnesium and copper into energy — just add water.

"A few years back I made an Instructable showing the process to make a emergency galvanic AA cell," Matthews explains by way of background. "Expanding on that project I will be making an emergency flashlight with hot swappable magnesium and copper water activated cells that can be easily recharge[d] with a new cathode and anode once depleted."

Designed to be used as an emergency light source, the compact torch and rather bulkier battery are both 3D-printed and designed for long-term storage in a suitably dry environment. Inside the galvanic battery housing are metals: magnesium ribbon as the anode and copper tape as the cathode, with cotton packing between them.

Once assembled, the galvanic batteries are effectively inert — there's no electrolyte, so no energy is produced. Activating them is simple: just add water, which is absorbed by the cotton and creates a bridge between cathode and anode — with even the minor mineral content of plain tap water good enough for the battery to output a solid 4.5V at 20mA, enough to light up an LED.

That LED, in Matthews' design, lives on an entirely home-brew circuit board — created using a 3D-printed template to mask a copper board ready for home etching in a mixture of hydrogen peroxide and hydrochloric acid. This board is then fitted with the LED and pogo pins before slotting into a 3D-printed framework, which can be clicked onto the top of an activated galvanic battery.

"For long term storage," Matthews notes, "I recommend getting some heat shrink PVC packing tubes and then to seal each battery module along with a small desiccant pack, this should give you an indefinite storage life until activating."

The project is documented in full on Instructables, complete with STL files for 3D printing.