Flexible Multifunctional Sensors for Wearable and Robotic Applications

Abstract

This review provides an overview of the current state‐of‐the‐art of the emerging field of flexible multifunctional sensors for wearable and robotic applications. In these application sectors, there is a demand for high sensitivity, accuracy, reproducibility, mechanical flexibility, and low cost. The ability to empower robots and future electronic skin (e‐skin) with high resolution, high sensitivity, and rapid response sensing capabilities is of interest to a broad range of applications including wearable healthcare devices, biomedical prosthesis, and human–machine interacting robots such as service robots for the elderly and electronic skin to provide a range of diagnostic and monitoring capabilities. A range of sensory mechanisms is examined including piezoelectric, pyroelectric, piezoresistive, and there is particular emphasis on hybrid sensors that provide multifunctional sensing capability. As an alternative to the physical sensors described above, optical sensors have the potential to be used as a robot or e‐skin; this includes sensory color changes using photonic crystals, liquid crystals, and mechanochromic effects. Potential future areas of research are discussed and the challenge for these exciting materials is to enhance their integration into wearables and robotic applications.

Year 2020: A Snapshot of the Last Progress in Flexible Printed Gas Sensors

“…Sensors play also a key role in development and implementation of robots, automation and control systems in the factory field. By equipping robotic devices with sensors, robotic machines have become increasingly capable of performing complex and more accurate tasks, allowing manufacturers to increase efficiency, productivity, and profitability [5].…”

“…-Air quality monitoring (indoor and outdoor) [8,9]; -Vehicle emission monitoring [10,11]; -Alarming of leakage of toxic and hazardous gases [12]; -Personal healthcare [13]; -Medical diagnosis [14]; -Food quality monitoring [15,16], Sensors play also a key role in development and implementation of robots, automation and control systems in the factory field. By equipping robotic devices with sensors, robotic machines have become increasingly capable of performing complex and more accurate tasks, allowing manufacturers to increase efficiency, productivity, and profitability [5].…”

Physical sensors for skin‐inspired electronics

“…Pyroelectric effects are widespread in ceramic crystals and polymers . The open‐circuit voltage of pyroelectric‐type temperature sensors can be calculated by the formula: , where k is a constant, p is the pyroelectric coefficient, is the permittivity, h is the thickness, and ∆T is the change in temperature …”

“…Finally, under the processing and instruction of the brain, the human body perceives and responds to the external stimuli . In recent years, inspired by the skin, novel electronics, such as wearable devices, electronic skin, and implantable electronic devices, have been widely studied, providing new opportunities for health monitoring, human disease diagnosis and treatment, and intelligent robots …”

Multifunctional Ultrahigh Sensitive Microwave Planar Sensor to Monitor Mechanical Motion: Rotation, Displacement, and Stretch

“…There is a high need for replacing traditional approaches for mechanical perturbation sensing using optical, for example, optical interferometry, or magnetic elements, for example, Hall-effect encoders, with highly accurate, low-cost, compact, and low-profile methods that are integrable with CMOS/MEMS technology. For such applications, compatibility of the sensor with large-area processing techniques and integrability into flexible devices are paramount to keep up with efforts in regards to expanding a multifunctional apparatus [41,42].…”