Abstract: A writing instrument comprising a housing including a flexible diaphragm and a sidewall forming a cavity therewithin, the diaphragm serving to distort in response to a movement of the sidewall, a plurality of strain gages attached to selected locations on the diaphragm, each strain gage having an electrical resistance and being responsive to distortion of the diaphragm and operative to produce a change in its electrical resistance corresponding to the distortion at its respective location, a reservoir capable of holding writing fluid and formed to be carried within the cavity, the reservoir including external ribs for frictionally engaging the sidewall and having a shaft extending therefrom, the shaft having a distal end for writing on a surface and a passageway for supplying writing fluid to the distal end, the distal end being movable in response to contact with the surface, whereby when the shaft is moved, such movement is transmitted through the reservoir and the sidewall to the diaphragm causing it to di