Self-assembled inorganic micro-display on plastic

We present the design and a method of construction for micro-displays via integrating free-standing micro light emitting diodes (LED) onto unconventional substrates using fluidic self-assembly. The micro LEDs are fabricated on AlGaAs substrates and released into a powder-like collection of microcomponents. The display substrate is a plastic template patterned with metal interconnects and a photopatternable polymer (SU8) to have a 4times4 array of binding sites each containing areas covered by a low melting point alloy. To assemble the display, the plastic substrate is inserted in a heated acidic ethylene glycol solution and the micro LEDs are released on the surface. Self-assembly of LEDs onto the binding sites aided by shape recognition, capillary forces resultant from the molten alloy, gravity, and fluidic forces completes the display. The self-assembly method allows for integration of crystalline semiconductor devices on plastics and other substrates that are incompatible with conventional microfabrication processes.