Nanoelectromechanical (NEM) switches have received widespread attention as promising candidates in the drive to surmount the physical limitations currently faced by complementary metal oxide semiconductor technology. The NEM switch has demonstrated superior characteristics including quasi-zero leakage behaviour, excellent density capability and operation in harsh environments. However, an unacceptably high operating voltage (4-20 V) has posed a major obstacle in the practical use of the NEM switch in low-power integrated circuits. To utilize the NEM switch widely as a core device component in ultralow power applications, the operation voltage needs to be reduced to 1 V or below. However, sub-1 V actuation has not yet been demonstrated because of fabrication difficulties and irreversible switching failure caused by surface adhesion. Here, we report the sub-1 V operation of a NEM switch through the introduction of a novel pipe clip device structure and an effective air gap fabrication technique. This achievement is primarily attributed to the incorporation of a 4-nm-thick air gap, which is the smallest reported so far for a NEM switch generated using a 'top-down' approach. Our structure and process can potentially be utilized in various nanogap-related applications, including NEM switch-based ultralow-power integrated circuits, NEM resonators, nanogap electrodes for scientific research and sensors.

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We describe a very simple breathing rate-sensing method that detects a significant electric current change between two metal electrodes on an oxidized surface. The current change is caused by the formation of a water layer from exhaled breath. We discovered that breathing onto the oxidized surface causes instant water condensation, and it generates 20 times increased current than that measured in the inhalation period. The condensed water quickly evaporates, enabling us to detect dynamic human breathing in real time. We also investigated the breathing rate sensor by varying the relative humidity, temperature, and breathing frequency and confirmed its potential for practical applications.

A surface micromachined offset-drive mechanism is demonstrated to address the pull-in problem of electrostatic actuation in microelectromechanical systems (MEMS). Similar to the vertical comb drive method, our offset-drive method uses fabricated electrodes that are laterally offset rather than directly opposite to each other. As a consequence, the electrodes are never engaged and are driven mostly by fringing fields. An offset electrode capacitance model is proposed for analysis. Simulations show that the proposed offset scheme may require lower operating voltages than some competing methods, and a full travel range can be achieved without pull-in. It is also found that drive performance is influenced by the structure's lateral gap. Lateral gaps smaller than a critical value are still susceptible to the pull-in problem. For devices on a planar semiconductor substrate, this method is electrically equivalent to the series capacitor mechanism due to the high substrate dielectric constant. We demonstrate that the substrate may be etched to improve the performance of this offset-drive method. An offset-drive test structure consisting of an aluminum beam suspended across two posts is designed and fabricated, with an etched substrate underneath. By measuring the maximum beam deflection, the offset-drive method is characterized experimentally.

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