Toys that let children draw by moving a magnetic pen over a tablet filled with magnetic particles can leak if they puncture the top surface. So Takara of Japan has invented a tablet that traps a suspension of magnetic particles in a honeycomb of tiny cells moulded from resin, each with a clear top (GB 2345270). The honeycomb is topped with a transparent protective layer. Even if a child stabs the top surface with pen, just one or two cells will be punctured, releasing only a very small quantity of fluid.
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