Back-Scratching T-shirt

There is nothing worse that having an itch you cannot scratch. The back-scratching t-shirt will provide around-the-clock back scratching capabilities through the use of a battery powered matrix of scratching elements embedded in the back of the shirt.

The battery (9 volt?) would be stored in the wearers pocket, or underwear. The 'scratching matrix' would consist of a 10x10 grid of small balls, each of which would contain a pin of similar sharpness to a human finger-nail.

The balls would sit next to each other to form a 10inch X 10inch coverage of the back.

Each ball would contain a small motor that would be able to move the scratching pin up, down, left and right, and combinations of these, to cover the area of the back covered by the ball. As there will be 100 balls in total, the entire area of the back should be covered. For larger backs, a larger grid may be required.

To operate the scratching matrix a small touch pad (connected to the battery unit) could be depressed for small periods of time. I would imagine that operating the scratching matrix for long periods could cause the motors to overheat and set fire to the shirt, so a cut-out device would need to be implemented.

Once depressed, a small current is passed through the grid, operating the motors in each scratching ball.

My only concern is the design of the scratching pin as it must be sharp enough to relieve itching, but not too sharp as to cause pain and/or bleeding. Perhaps discarded human/animal finger/toe nails could be used?