Universal, Fully 3D Printable Tripod Mount for Smartphones
Print jaws in a flexible material.
Print the jaws in NinjaFlex (or your flexible filament of choice) with fairly low infill - it needs to be able to deform a couple millimeters for the tensioning mechanism to work correctly, and the flexible material protects phones without cases. I used 10% infill.
Use the long cylinders on the jaws to pull them through the mounting holes, then cut them off once assembled.
The hole on the bottom should be able to thread onto a standard tripod (with a bit of effort).
The tensioning mechanism is loosely based on vernier calipers. Two sets of holes with different spacing allows one set of holes to line up every 2mm, while keeping the pin relatively thick. Place your phone between the jaws, squeeze them together lightly, and push the pin into the hole that lines up.
I printed it on a Rep 2 with a glass build plate coated with a glue stick. My slicing profiles are attached.