I am on the mailing list for regular updates on a pen that can be used to create 3 dimensional shapes. The shapes are not solid but I think I figured out how I can use the pen effectively in class. In order to create the shapes, the pen relies on people tracing shapes on paper and then using more plastic to spot weld corners together.
In the past, I've had students create their own 3D shapes out of construction paper, scissors and tape. So with the 3D pen, I could easily have the students create their own patterns and use the pen to create the shapes. Further more, it would be fairly easy to include markers for units such as millimeters.
When a student starts creating the cube, they would make sure to create each side with all the smaller units so once the whole shape is assembled, they can see the units within the figure and can count the cubic millimeters.
This could easily be done with rectangular prisms, triangular prisms, etc. I know my students often miss that little connecting piece. In addition, it would allow my students to see how you go from 2 dimensional pieces into 3 D shapes.
For instance, a cylinder is made up of a rectangle and two circles and those are used to create the volume or surface area formulas. I might splurge in a pen and try this in my Geometry class. We'll see.