The Triangle is a Pneunet design that is based on the Slow Pneunet architecture. It is designed by Sabina Barcucci.
The fabrication process is described in detail on the FabAcademy 2015 page.
The molds are available for download on the Fab Academy github page.
Converted Molds to STL: musclenurbs.zip
The air inlet is the basic Slow Pneunet inlet, as shown in the pic below: