Manipulating micron scale items

Micron scale dielectric items are manipulated by methods and apparatus taking advantage of spatially non-uniform field. Such fields give rise to a force on dielectric items, directing them generally toward regions of more concentrated field. The electrode may be elongated, either unitary, with a generally planar counter electrode, or dual, such as parallel pins, loops or plates. If dual, particles are generally attracted to regions of high field concentration, including tips, edges and spaces between electrode conductors. Items can be granular, threadlike, or sheets, and microelectronic parts and other shapes. Items can also be collected directly into a recess of a pharmaceutical material delivery microchip, with a conductive membrane of the microchip acting as a manipulating electrode. Items are attracted without regard to their surface charge, or the polarity of the field, which can be AC or DC. Charging, or knowing the charge of items to be manipulated is not necessary. The amount of material collected can be precisely controlled by varying parameters of collection, such as distance between the electrode and the items, distance between dual conductors, size (diameter, length) of the conductors, any dielectric sheathing thereof, and voltage. Elongated electrodes can be used to manipulate items into and from recesses, such as wells of microtitre trays, microchips, and semiconductor chips. Several recesses can be used to calibrate an array of collecting and depositing electrodes and deposits. Items can be removed from fluids, such as aerosol dispersions, and an air cleaner is also disclosed. Dielectrophoretic forces are exploited. Techniques and apparatus for depositing such items include charged targets and targets with electrodes designed to create a non-uniform field.