[Jethro Tull] is a name you may well associate with a 1970s prog/folk rock band featuring a flautist, but the original [Tull] was an inventor whose work you benefit from every day. He was a British lawyer and landowner who lived over the turn of the 18th century, and who invented among other things the mechanical seed drill.
Were [Tull] alive today he would no doubt be impressed by the work of [Akash Heimlich], who has created an exquisite vacuum seed placer for his rooftop hydroponic lettuce farm. Unlike the continuous rows of seed on the Berkshire earth of [Tull]’s farm, the lettuce seed must be placed in an even grid on a foam substrate for the hydroponic equivalent. This was an extremely tedious task when done by hand, so [Akash] set about automating the process with a vacuum seeder that is a thing of beauty.
It uses a simple yet effective mechanism involving a row of pipettes connected to a vacuum line, that are rotated over a vibrating hopper of seeds from which each one collects a single seed, before being rotated back over the foam where the seeds are dropped in a neat row through 3D-printed funnels. The foam is advanced, and the process is repeated until there is a neat grid of seeds. In only four minutes it can deliver 150 seeds, reducing several hours work into under half an hour.
The whole machine is controlled by an Arduino, with a couple of stepper motors to move foam and pipettes alongside the vibrator motor. You can see its operation in the video below the break.