Dry powder electrostatic deposition method and apparatus

Abstract

A method and apparatus are presented for electrostatic deposition of dry powder to a tablet, capsule, or a specific area of any of a wide range of pharmaceutical substrates. The apparatus includes: a magnetic brush having a rotatable multi-pole magnetic core and a stationary outer shell; a developer supply for supplying a magnetic developer powder, consisting of a magnetic carrier particles and pharmaceutical dry powder particles, to the magnetic brush; a print head on the outer shell; a tablet or other pharmaceutical substrate arranged in spaced relation to the print head to define a pharmaceutical powder transfer region through which the substrate can be moved. The print head includes an array of microchannels for forming a plurality of parallel lines of developer in the channels, a corresponding plurality of transfer electrodes located in the microchannels for selectively transferring pharmaceutical powder from the lines to a substrate, driver circuitry for generating and applying transfer signals to the transfer electrodes, a power supply connection for applying power to the drive circuitry, a print signal input connection for applying print signals to the print head, and a logic and control circuit for applying the print signals to the drive circuitry. In one embodiment the width of an individual microchannel print head and the rotating multipole magnetic core is approximately the same dimension as the tablet or substrate to which pharmaceutical powder is to be deposited. In a further embodiment individual microchannel print heads can be arranged along the length of the shell to simultaneously deposit pharmaceutical powder to an array of tablets. In still a further embodiment the microchannel print head is shaped to conform to the tablet or capsule geometry to enhance deposition in three dimensions. In another embodiment the microchannel print head is formed on a silicon substrate onto which are also formed a multiplicity of individual drive circuits connected through separate conductive paths to individual transfer electrodes. In a further embodiment all the microelectronic circuitry necessary for the operation of the integrated microchannel print head is formed on the silicon substrate.