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Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and emphasizing nontechnical issues such as business, regulatory, and ethical considerations. Additionally, we look at future intelligent flexible sensors. In proposing a comprehensive roadmap, we hope to steer research efforts towards common goals and to guide coordinated development strategies from disparate communities. Through such collaborative efforts, scientific breakthroughs can be made sooner and capitalized for the betterment of humanity.

For decades, the revolution in design and fabrication methodology of flexible capacitive pressure sensors using various inorganic/organic materials has significantly enhanced the field of flexible and wearable electronics with a wide range of applications in aerospace, automobiles, marine environment, robotics, healthcare, and consumer/portable electronics. Mathematical modelling, finite element simulations, and unique fabrication strategies are utilized to fabricate diverse shapes of diaphragms, shells, and cantilevers which function in normal, touch, or double touch modes, operation principles inspired from microelectromechanical systems (MEMS) based capacitive pressure sensing techniques. The capacitive pressure sensing technique detects changes in capacitance due to the deformation/deflection of a pressure sensitive mechanical element that alters the separation gap of the capacitor. Due to advancement in state‐of‐the‐art fabrication technologies, the performance and properties of capacitive pressure sensors are enhanced. In this review paper, recent progress in flexible capacitive pressure sensing techniques in terms of design, materials, and fabrication strategies is reported. The mechanics and fabrication steps of paper‐based low‐cost MEMS/flexible devices are also broadly reported. Lastly, the applications of flexible capacitive pressure sensors, challenges, and future perspectives are discussed. [ABSTRACT FROM AUTHOR]

The state-of-the-art electronics technology has been an integral part of modern advances. The prevalent rise of the mobile device and computational technology in the age of information technology offers exciting applications that are attributed to sophisticated, enormously reliable, and most mature CMOS-based electronics. We are accustomed to high performance, cost-effective, multifunctional, and energy-efficient scaled electronics. However, they are rigid, bulky, and brittle. The convolution of flexibility and stretchability in electronics for emerging Internet of Everything application can unleash smart application horizon in unexplored areas, such as robotics, healthcare, smart cities, transport, and entertainment systems. While flexible and stretchable device themes are being remarkably chased, the realization of the fully compliant electronic system is unaddressed. Integration of data processing, storage, communication, and energy management devices complements a compliant system. Here, a comprehensive review is presented on necessity and design criteria for freeform (physically flexible and stretchable) compliant high-performance CMOS electronic systems. [ABSTRACT FROM AUTHOR]

High performance flexible electronics promise innovative future technology for various interactive applications for the pursuit of low-cost, light-weight, and multi-functional devices. Thus, here we show a complementary metal oxide semiconductor (CMOS) compatible fabrication of flexible metal-oxide-semiconductor capacitors (MOSCAPs) with high-κ/metal gate stack, using a physical vapor deposition (PVD) cost-effective technique to obtain a high-quality Ge channel. We report outstanding bending radius ∼1.25 mm and semi-transparency of 30%. (© 2014 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We report the inherent increase in capacitance per unit planar area of state-of-the art high- κ integrated metal/insulator/metal capacitors (MIMCAPs) fabricated on flexible silicon fabric with release-first process. We methodically study and show that our approach to transform bulk silicon (100) into a flexible fabric adds an inherent advantage of enabling higher integration density dynamic random access memory (DRAM) on the same chip area. Our approach is to release an ultra-thin silicon (100) fabric (25 µm thick) from the bulk silicon wafer, then build MIMCAPs using sputtered aluminium electrodes and successive atomic layer depositions (ALD) without break-ing the vacuum of a high- κ aluminium oxide sandwiched between two tantalum nitride layers. This result shows that we can obtain flexible electronics on silicon without sacrificing the high density integration aspects and also utilize the non-planar geometry associated with fabrication process to obtain a higher integration density compared to bulk silicon integration due to an increased normalized capacitance per unit planar area. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Monitoring, measuring, and controlling electronic systems in space exploration, automotive industries, downhole oil and gas industries, marine environment, geothermal power plants, etc., require materials and processes that can withstand harsh environments. Such harshness can come from the surrounding temperature, varying pressure, intense radiation, reactive chemicals, humidity, salinity, or a combination of any of these conditions. Here, recent progress in the development of flexible and stretchable electronic devices for harsh‐environment applications is reviewed. Studies are considered on how the selection of a specific material is critical for a particular application and how the selection of the material plays a critical role in sustained performance. Certain examples are presented for selected applications. Works on methods and designs for achieving flexibility and stretchability in devices designed for harsh environments are also investigated. Finally, studies on packaging techniques that enable deployment of conventional electronic devices in harsh‐environment applications are considered, with a few examples described. [ABSTRACT FROM AUTHOR]