Nanoelectromechanical system (NEMS) sensors and actuators could be of use in the development of next generation mobile, wearable, and implantable devices. However, these NEMS devices require transducers that are ultra-small, sensitive and can be fabricated at low cost. Here, we show that suspended double-layer graphene ribbons with attached silicon proof masses can be used as combined spring-mass and piezoresistive transducers. The transducers, which are realized using processes that are compatible with large-scale semiconductor manufacturing technologies, can yield NEMS accelerometers that occupy at least two orders of magnitude smaller die area than conventional state-of-the-art silicon accelerometers. With our devices, we also extract the Young's modulus values of double-layer graphene and show that the graphene ribbons have significant built-in stresses.

Carbon dioxide is a vital gas for life on Earth, a waste product of human activities, and widely used in agriculture and industry. Its accurate sensing is therefore of great interest. Optical sensors exploiting the mid-infrared light absorption of CO 2 provide high selectivity, but their large size and high cost limit their use. Here, we demonstrate CO 2 gas sensing at 4.2 µm wavelength using an integrated silicon waveguide, featuring a sensitivity to CO 2 of 44 % that of freespace sensing. The suspended waveguide is fabricated on a silicon-on-insulator substrate by a single-lithography-step process, and we route it into a mid-infrared photonic circuit for on-chipreferenced gas measurements. Its demonstrated performance and its simple and scalable fabrication make our waveguide ideal for integration in miniaturized CO 2 sensors for distributed environmental monitoring, personal safety, medical, and high-volume consumer applications.Carbon dioxide (CO 2 ) is an atmospheric trace gas and, being the carbon source in the carbon cycle, it is vital to life on Earth. It is also a waste product of human activities and massively used in agriculture and industry. The atmospheric CO 2 concentration is growing at an ever increasing rate and reached 410 ppm in 2018 [1]. Besides affecting Earth's climate [2,3], elevated CO 2 levels increase air pollution mortality [4], and gross leakage of CO 2 puts personnel at risk of asphyxiation [5]. Indoors, high CO 2 levels deteriorate human cognitive function and decisionmaking [6][7][8], with consequences spanning from reduced attention and productivity in classrooms and offices [6,7] to an increased risk for car and airplane accidents [8]. Extensive and accurate sensing of CO 2 is therefore crucial.Optical CO 2 sensors would benefit most applications, due to their high selectivity, fast response, and minimal drift, compared to electrochemical and metal-oxide semiconductor-based sen-arXiv:1907.06967v1 [physics.app-ph]

Abstract. Unmanned aircraft systems (UASs) could provide a cost-effective way to close gaps in the observation of the carbon cycle, provided that small yet accurate analysers are available. We have developed a COmpact Carbon dioxide analyser for Airborne Platforms (COCAP). The accuracy of COCAP's carbon dioxide (CO2) measurements is ensured by calibration in an environmental chamber, regular calibration in the field and by chemical drying of sampled air. In addition, the package contains a lightweight thermal stabilisation system that reduces the influence of ambient temperature changes on the CO2 sensor by 2 orders of magnitude. During validation of COCAP's CO2 measurements in simulated and real flights we found a measurement error of 1.2 µmol mol−1 or better with no indication of bias. COCAP is a self-contained package that has proven well suited for the operation on board small UASs. Besides carbon dioxide dry air mole fraction it also measures air temperature, humidity and pressure. We describe the measurement system and our calibration strategy in detail to support others in tapping the potential of UASs for atmospheric trace gas measurements.

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A motion tracker measures acceleration and rotation in three dimensions, sufficient for a complete determination of the motion. In this article, a rollercoaster ride is analysed with reference to motion tracker data. The use of this type of data in education is discussed as a way to deepen students' understanding of concepts related to force and acceleration.