How do I design a pen?

This pen has multiple uses like it can hold a smartphone of thickness 7.5mm and the upper part the pen nob has a rubber material which can also operate the touch screen of the smartphone. It is actually a mini project for the CAD-CAM subject, any help would be appreciated. I would like to design it on Solidworks, thankyou.

Accepted answer

The model seems to be simple; the outer body doesn't need any aid, the inner mechanism is what you're after...

From the image, it looks like a twist pen.
It has a helical path that moves the pen's tip forwards when rotated in one direction and retracts it when rotated in the other direction, just like a lipstick (Check the attached GIF).

This might help, too:

1 Other answer

The ballpoint is a good study in cam mechanisms.

And, there are plenty of searchable patents online.