Recent paradigms, such as smart cities/homes, Internet of Things or portable and implantable healthcare systems, require the use of flexible and conformal sensors that can be assembled to arbitrarily 3D complex shapes. A good set of simple and available models is of paramount importance to help designing and fabricating such devices. In this work, analytical expressions for the bending plane, the curvature radii and the stress/strain distributions of multilayer composite devices are derived for the cases of uniaxial and biaxial plane stress and plane strain and generalised plane strain. The analytical results are summarized, and two case-studies are analysed and compared with the help of these models: bilayer and trilayer hinges for self-assembled structures and rolled up flexible substrates with sensors on top. The dependence of the curvature radii and strain and stress distributions on several mechanical properties of the composite is assessed. The applicability of these models to support the design of flexible sensors, electronics or haptic devices is discussed and their practical limitations analysed.

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With the emergence of the Node.js ecosystem, JavaScript has become a widely used programming language for implementing server-side web applications. In this article, we present the first empirical study of static code analysis tools for detecting vulnerabilities in Node.js code. To conduct a comprehensive tool evaluation, we created the largest known curated dataset of Node.js code vulnerabilities. We characterized and annotated a set of 957 vulnerabilities by analyzing information contained in npm advisory reports. We tested nine different tools and found that many important vulnerabilities appearing in the OWASP top-10 are not detected by any tool. The three best performing tools combined only detect up to 57.6% of all vulnerabilities in the dataset, but at a very low precision of 0.11%. Our curated dataset offers a new benchmark to help characterize existing Node.js code vulnerabilities and foster the development of better vulnerability detection tools for Node.js code.