Beautiful summer's day? Naturally I should spend it inside designing a Mark VIII sonic screwdriver... :unsure
I wanted to evoke a sense that Gallifreyan and TARDIS design and technology went into the making of my sonic, as well as incorporate aspects of previous screwdrivers.
Beginning with the handle, which is hexagonal, based on the TARDIS console itself, since the old girl produced Eleven's Mark VII and possibly the previous models as well. It has the impression of the hex-circle walls of Ten and Eleven's TARDIS, as well as the station dividers of the Fourth Doctor's console. This leads to the acrylic tube within a tube, basically a miniature of the TARDIS console core from Ten's ship.
The collar, rings and upper shaft are a throwback to the Mark II-IV design, with the addition of rotating rings with finely engraved Gallifreyan numbers on them, for manually adjusting the sonic setting, though naturally this can also be done psychically, thanks to the Metebelis Crystal emitter (see below). Letter settings change dependent on whether the sonic is extended or not, and other spacey-wacy stuff.
Extending up through the collar and rings, and along the upper shaft are three, flat, metallic prongs which hold the emitter, which is a throwback to the Mark II-IV emitters, only turned horizontally. These prongs can extend an additional 20mm (approx), allowing the emitter a wider dispersion field, as well as a fun, "clacking" noise.
In the center of the emitter is a perfect, blue, sphere-cut, Metebelis Crystal, acquired by the Third Doctor on Metebelis III. It helps to power the sonic via fluon radiation and through it's natural ability to amplify the psychic power of it's holder. This also allows for neural interface with the sonic for those properly attuned with the device.
Practical Design Details:
I imagine either a laser diode or very powerful LED in the base of the sonic, which shines through the length of the entire hollow center structure and hits the Crystal in the emitter, which hopefully can be made of some translucent, refracting material so that the laser causes it to shine. It would be ideal if this light also illuminated the lower, clear "TARDIS CONSOLE" shaft. And if there's room for a speaker and sound chip for the accompanying sound effect, even better.
Around the electronics in the base/handle sits a spring-loaded mechanism, which should both move the "TARDIS Central Core" innards up through the clear tube of the lower shaft, and simultaneously extend the prongs, which should be attached to the top of the "TARDIS Central Core" inside the collar and rings section.
When retracted, the crystal should nest flush against what could be a rubber ring at the tip of the upper shaft.
Reference Material:
I've included a photo collage of various parts of the TARDIS, previous screwdrivers and other Doctor Who technology that served as source material for the design elements.
EDIT: Obviously, the overall length should read 250mm and 230mm for extended and retracted measurements respectively. As I think a 2.5 meter long screwdriver would be difficult to slide into one's pocket
