Transience mechanisms for secured transient electronics

The dissertation presents two classes of triggered chip self-destruction or transience towards realization of highly secured microchips. The transience mechanisms developed in this study are required to be simple, low cost and designed in way that they can be easily "added-on" to any off-the-shelf (OTS) silicon (Si) microchips. We first introduced two mechanisms through which surface features of OTS Si chips are destroyed. In the first method to achieve surface destruction (transience) a microfluidic plane was fabricated over the target chip and with perfectly sealed microfluidic reservoirs containing corrosive agents which are released on the chip surface on application of a trigger to execute transience action. The second surface transience mechanism utilizes a solid-state energetic exothermal energy release layer that when ignited melts the surface metal features of the microchips. The exothermic energy release layer was developed as a spin-coated nanothermite thin film with a self-assembled CuO/Al nanothermite mixture densely dispersed in a napalm-B gelling agent. This thin film could be ignited through resistive heating or through an electric spark. Both methods are developed as an add-on technique without requiring any specialized chip design and are shown to successfully destroy OTS silicon test microchips with electrical components in a few seconds. The second type of transience mechanism developed in this study is termed as volumetric transience where transience occurs through a shattering pathway. The transience mechanism follows Griffith's crack propagation theory in which the boundaries iv of existing microcracks in the form of partial grooves introduced on the backside of the OTS silicon chip under a critical stress, applied by expandable actuator materials, propagate freely resulting in physical shattering. In this type of mechanism (OTS) CMOS Si chips are reduced to silicon dust through a triggered transience mechanism. Four types of expandable actuator materials have been used to act as vehicles of transience. Two materials are based on superabsorbent (SA) polymers which can absorb and retain water, swelling to >1000 times their original volume. The other two materials utilized thermally expandable (TE) materials which expand >100 times their original volume on heating. The transience mechanisms developed through these materials are triggered either in the presence of water or through heat. Material characterization and modeling has been performed to develop a customizable transience volumetric mechanism from these actuator materials without full knowledge of material properties. Triggered transience time has been observed to range between less than a second to several minutes.