Sub-threshold addressing and erasing in a magneto-electrophoretic writing medium

A writing system comprising:

• a magneto-electrophoretic display including:
• a first electrode that is light-transmissive,
• a second electrode,
• a magneto-electrophoretic medium disposed between the first electrode and the second electrode, the magneto-electrophoretic medium comprising composite particles, the composite particles comprising a combination of a magnetic pigment and a non-magnetic pigment, the composite particles being synthesized via sintering, dispersion polymerization, emulsion, or mini-emulsion polymerization;
• a stylus having a body having a first magnetic end;
• and
• a voltage controller configured to supply voltage between the first electrode and the second electrode;
• the writing system having a viewing surface at the first electrode;
• and
• the writing system comprising two modes:
• a global erase mode in which the voltage controller applies a first voltage to the magneto-electrophoretic medium, the first voltage being sufficient to drive the charged magnetic particles toward the viewing surface at the first electrode, and
• a local erase mode in which the voltage controller applies a sub-threshold second voltage on the magneto-electrophoretic medium, and supplemental magnetic field is applied by the stylus on the magneto-electrophoretic medium simultaneously with the sub-threshold second voltage, the sub-threshold second voltage being greater than zero but insufficient to drive the charged magnetic particles to the viewing surface at the first electrode within five seconds, but the simultaneous application of the sub-threshold second voltage and the supplemental magnetic field being sufficient to drive the charged magnetic particles to the viewing surface at the first electrode and to cause the magneto-electrophoretic medium to switch from a first state to a second state, wherein the sub-threshold second voltage comprises a first time-varying waveform, the local erase mode comprising a step of measuring a remnant voltage on the magneto-electrophoretic medium;
• and if an absolute value of the remnant voltage is higher than 0.3 V, modifying the first time-varying waveform to diminish the remnant voltage on the magneto-electrophoretic medium.