It is a perfect use of Objet's multiple material 3D Printing to make light travel through complex paths and using the clear for multitouch interfaces. Check out at the 3 minute mark where they seem to pause the 3D Printer, insert the electronics and continue to 3D print to embed the product... very cool. If you would like to read more you can download their paper on the subject.
Printed Optics is a new approach to creating custom optical elements for interactive devices using 3D printing. Printed Optics
enable sensing, display, and illumination elements to be directly
embedded in the body of an interactive device. Using these elements,
unique display surfaces, novel illumination techniques, custom optical
sensors, and robust embedded components can be digitally fabricated for
rapid, high fidelity, customized interactive devices.
is part of our long term vision for the production of interactive
devices that are 3D printed in their entirety. Future devices will be
fabricated on demand with user-specific form and functionality. Printed Optics explores the possibilities for this vision afforded by today's 3D Printing technology.