Introduction

The concept of “ambient electronics”, referring to electronics embedded extensively in common environments, has emerged in recent years. Embedding intelligence in surfaces such as walls, ceilings, clothes and packages will improve safety, security and convenience in everyday life [1]. We will refer to these novel applications as “smart systems-on-foil”. Such systems require characteristics that are not met by silicon-based technologies, for example mechanical flexibility and large-area integration at a low cost. The standard crystalline and amorphous silicon technologies require high processing temperatures which are incompatible with flexible surfaces [2]. The possible alternative solutions, such as the thin chip technology [3] and substrate transfer from silicon-on-insulator wafers [4], currently require a fabrication procedure that is not suitable to large-area applications, is complex and, hence, costly. Therefore, there is a growing need for technologies to build electronics with different characteristics from what mainstream silicon technology provides.