With the rapid development of society in recent decades, the wearable sensor has attracted attention for motion-based health care and artificial applications. However, there are still many limitations to applying them in real life, particularly the inconvenience that comes from their large size and non-flexible systems. To solve these problems, flexible small-sized sensors that use body motion as a stimulus are studied to directly collect more accurate and diverse signals. In particular, tactile sensors are applied directly on the skin and provide input signals of motion change for the flexible reading device. This review provides information about different types of tactile sensors and their working mechanisms that are piezoresistive, piezocapacitive, piezoelectric, and triboelectric. Moreover, this review presents not only the applications of the tactile sensor in motion sensing and health care monitoring, but also their contributions in the field of artificial intelligence in recent years. Other applications, such as human behavior studies, are also suggested.

In recent years, society has paid great attention to health care and environmental safety. Thus, research on advanced sensors for detecting substances that can harm health and the environment has been developed rapidly. Another popular target for detection techniques is disease-expressing materials that can be collected from body fluids. Carbon, which has outstanding electrochemical properties, can come from a variety of sources and has many morphological shapes, is nevertheless an environmentally friendly material. While carbon nanomaterial has become one of the most common targets for high-tech development, electrochemical voltammetry has proven to be an effective measurement method. Herein, the paper proposes a currently developed carbon nanomaterial along with research on a modified carbon material. Moreover, four common voltammetry methods and related works are also introduced.

Carbon nanofibers (CNFs) are the most basic structure of one-dimensional nanometer-scale sp² carbon. The CNF’s structure provides fast current transfer and a large surface area and it is widely used as an energy storage material and as a sensor electrode material. Electrospinning is a well-known technology that enables the production of a large number of uniform nanofibers and it is the easiest way to mass-produce CNFs of a specific diameter. In this review article, we introduce an electrospinning method capable of manufacturing CNFs using a polymer precursor, thereafter, we present the technologies for manufacturing CNFs that have a porous and hollow structure by modifying existing electrospinning technology. This paper also discusses research on the applications of CNFs with various structures that have recently been developed for sensor electrode materials and energy storage materials.

Nanofibers have gained much attention because of the large surface area they can provide. Thus, many fabrication methods that produce nanofiber materials have been proposed. Electrospinning is a spinning technique that can use an electric field to continuously and uniformly generate polymer and composite nanofibers. The structure of the electrospinning system can be modified, thus making changes to the structure, and also the alignment of nanofibers. Moreover, the nanofibers can also be treated, modifying the nanofiber structure. This paper thoroughly reviews the efforts to change the configuration of the electrospinning system and the effects of these configurations on the nanofibers. Excellent works in different fields of application that use electrospun nanofibers are also introduced. The studied materials functioned effectively in their application, thereby proving the potential for the future development of electrospinning nanofiber materials.

Radio Frequency Identification (RFID) technology, capable of wirelessly processing large amounts of information, is gaining attention with the advancement of IoT technology. RFID systems can be utilized as Wireless Sensor Network (WSN) technology by introducing sensing materials responsive to external environmental stimuli. To achieve effective information communication and sensing capabilities, various types of nanomaterials are being used as various components of RFID sensors. This paper provides an overview of the RFID sensor system and the nanomaterials used in their composition. Polymers that can achieve flexibility are attracting more attention as user-friendly substrates as demand for them increases in the wearable market. Additionally, advancements in inkjet printing technology, allowing cost-effective and simple production of components, introduce inks and manufacturing methods utilizing various nanomaterials such as metal nanoparticles, carbon materials, and composites. Furthermore, nanomaterials utilized as sensing materials enable the detection of various external environments with high sensitivity and a wide detection range. Consequently, RFID sensor systems that achieve wireless detection in a variety of environments are actively utilized in many applications. By analyzing the current research progress and problems faced in RFID sensor technology, this paper suggests future research directions for its development as a next-generation wireless sensor system.