Microdevice arrays formed by magnetic assembly

A method of altering orientation of microdevices having a largest linear dimension of less than 500 flM, comprising:

• positioning the microdevices in an array on an arraying chip comprising a substrate having an array of embedded magnetizable magnetic elements, the magnetizable magnetic elements each having an element predetermined preferential axis of magnetization that exerts magnetic forces in response to an external magnetic field, where the microdevices are disposed according to a first orientation relative to the magnetic elements,
• wherein an induced magnetization in its absolute magnitude along the element predetermined preferential axis of the magnetization of each element is at least 20% more than an induced magnetization of said element along at least one other axis;
• and
• applying at least first and second external magnetic fields in a sequence such that selected ones of the arrayed micro devices are re-oriented by at least 90°.

An article of manufacture, comprising:

• a set of microdevices each having a longest linear dimension of no more than 1 mm, a thickness of less than 50 μM;
• and
• a bar of magnetic material disposed off-center in said microdevice,
• wherein each bar is sized and dimensioned to be complementary to dimensions of magnetic bars within an arraying chip,
• wherein each of the microdevices has a predetermined preferential axis of magnetization, and
• wherein an induced magnetization in its absolute magnitude along the preferential axis of the magnetization of said microdevice is at least 20% more than an induced magnetization of said microdevice along at least one other axis.