Through the use of digital printing methods (such as ink-jet), custom electronic systems can be additively fabricated in an on-demand fashion. This can be approached by formulating solution-based inks of conductors, dielectrics and semiconductors, and directly printing these materials to form logic circuits, sensors, memory and power sources that when integrated can provide devices to address a number of flexible and wearable electronics applications. In order to further improve the performance these devices, a hybrid approach can be followed where prefabricated Si-CMOS components are integrated into the printed system to provide functionality that is difficult to achieve with all-printed components (such as wireless communication and high resolution analog-to-digital conversion). For some applications this approach can provide the optimal balance between electrical and mechanical performance, customizability and cost. Examples of both all-printed and mostly-printed sensor systems will be described. In order to digitally, additively fabricate high performance electronic devices we have developed a system of mesoscale assembly for arbitrary patterning of microelectronic components. Taking inspiration from xerography (where large numbers of micron-sized toner particles are assembled electostatically), a method of programmable assembly of pre-fabricated microchips using electric fields will be described. Here, small silicon pieces (100s of microns in size) are fabricated and formulated into a solution-based ink. The chips are pre-treated to bear a pattern of electric charge, so that they respond to dynamic electric fields which are used to freely orient and transport them into position with micron-level accuracy. Once correctly assembled, the chips are then transferred and fixed to a final substrate, and interconnections are made. Such a system should enable a digital, print-like method of assembling and integrating high-performance electronics over large areas and onto flexible substrates.
Citation
Whiting, G. L. Digital Fabrication of Flexible Electronic Systems. Semicon West 2014.
