Developing materials is basic in wearable technology. The materials had better be stretchable, comfortable, bendable, portable, light and flexible enough to move with the users. That’s why flexible materials are widely used in health diagnosis, sports monitoring, rehabilitation and entertainment.

Sensors are devices that detect some types of input from the physical environment and respond to them.  Sensors in wearable technology are also wearable, and they are widely used in measuring health-related symptoms.

In this issue, we will see some articles about the technique involving in smartwear materials and sensors. Two of our editor board members offered articles of this topic.

Prof. Shufang Li from Beijing University of Posts and Telecommunications discussed the different realization methods and performance index requirements of wearable antenna (a new form of wearable devices), introduced the research situation of wearable antenna in China and other countries in recent years, and analyzed the development trend of wearable antenna. Prof. Liping Xie from Northeastern University summarized the development of flexible sensors in recent years, discussed how to construct high-performance flexible stress sensors based on deep analysis and investigation on the working principle and structural design of flexible stress sensors, pointed out the existing problems and looked forward to the development trend of flexible stress sensors. These two articles used to be published in Chinese and it’s our honor to get the two professors’ authorization to have the articles translated and republished. A lot of other interesting researches and reviews were collected in this issue as well.

In recent years, a large number of wearable devices have emerged; and users have higher and higher functional requirements for wearable devices. However, the realization of complex functions of wearable devices often depends on the real-time acquisition of multi-channel sensing signals. Taking the wearable 8-channel PVDF sensor system as an example; this paper studies the functional requirements of this kind of system. It is found that the flexible ultra-thin and long endurance time are two obvious characteristics of this kind of equipment. The key technical problems of the system are completed, such as the selection of MCU, the coding design of multi-channel sensing data, the transmission mode design of multi-channel sensing data and the low power consumption design of the system. A practical design scheme of reliable wearable multi-channel sensor system is designed. This scheme also provides a reliable reference for the design and development of wearable multi-channel sensor system.

A set of wearable granary working environment sensing and security alarm system is developed to ensure the safety of granary staff. The gas sensor, piezoelectric ceramic chip, infrared transmitting and receiving tube and photosensitive resistance are used as the core components of each circuit module to collect the gas concentration signal, human respiration intensity signal, pulse intensity signal and light signal in the granary. AD0809 module chip is used to convert analog data into digital data and send it to MCU for information processing to make alarm judgment. At the same time, PTR2000 module is used to transmit the sensor data to the upper computer. The upper computer determines whether to alarm through data comparison, and transmits the alarm signal to the mobile phone through Wi-Fi in real time. Each module cooperates with each other, information real-time transmission to complete the detection of granary environment and danger alarm. The test results show that the system can meet the safety operation requirements of large and medium-sized state-owned grain depot.

By using flexible sensors and micro-control units, a wireless controller that can be integrated into clothing for cross-platform music control has been designed and implemented, providing a new idea for making a simple and low-cost flexible wearable sensing system. The design and implementation of a wireless controller that can be integrated into clothing for cross-platform music control provides a new idea for the preparation of a simple and low-cost flexible wearable sensing system. Based on the flexible fabric sensing material, a simple structured sensor piece is proposed as a button for the controller with good wearing comfort. The sensor element is capable of sensing finger presses up to 15kPa. ESP32 is used as a micro-control unit for sensing signal acquisition and data processing. Using the Bluetooth chip integrated inside the ESP32, the controller can be connected with terminal devices of different platforms for wireless data transmission. The results show that the prepared wireless music controller can be stably connected with both Windows computer terminal and Android cell phone terminal, and the sensor recognition accuracy of finger press is 99.7%, which indicates that the flexible fabric sensor has a broad application prospect in the field of wearable devices.

Aiming at the application requirements of fabric electrodes in wearable electronic clothing, the current materials and structure types of fabric electrodes are introduced respectively, the influence of fabric electrodes materials and structure parameters on the stability of ECG signal acquisition is analyzed, the use principle of fabric electrodes and the relationship between signal acquisition stability and comfort are summarized, and the application prospects and development direction of fabric electrodes in wearable electronic clothing are prospected in the future.

The detection mechanism of enzyme-free glucose electrochemical sensors, the research progress of enzyme-free glucose sensors based on composite materials such as noble metals, transition metals and doped carbon nanomaterials, and the latest progress of new wearable enzyme-free glucose detection devices are reviewed. With the development of science and technology, enzyme-free glucose sensors will potentially be applied to the in vivo detection of animal and plant species, which will become a hot spot for new research.

The smart mask is a new type of mask with active air supply and breathing. It adopts an external electric fan-forced air supply system, which can effectively reduce the user’s breathing load and achieve the purpose of improving comfort and user experience. However, in the current market, the function of smart masks is relatively simple with weak practicability and limited application. Based on these situations and in the research of a large number of smart masks and other types of masks, their application scenarios, advantages and disadvantages of the current technologies used in smart masks are analysed and compared to demonstrate their advantages in comfort and functionality. In terms of application prospects, new technologies can be integrated into the research and development of smart masks, providing new ideas for the research and development of new masks, which is crucial to the future market development of smart wearable products.

The sense in simulated reality is the key of human-computer interaction technology. Force feedback interaction technology is an important factor to realize simulated force sense in virtual reality. It can truly reproduce the physical information such as the mass, inertia and hardness of things in the virtual world. This paper summarizes the flexible sensors commonly used in force feedback technology and the development and research status of virtual reality wearable electronic clothing equipment based on force feedback technology, summarizes the principles of several force feedback structures, analyzes and compares their characteristics and main application fields. This paper briefly describes the prospect of force feedback technology, summarizes the trend of high-precision, multi-modal and multi-point interaction of force feedback equipment in the future, and puts forward some suggestions on miniaturization, softness and authenticity of force feedback technology in combination with the application characteristics of wearable electronic clothing.

Organic electrochemical transistors are flexible in design with characteristics such as miniaturisation, biocompatibility and amplification and are one of the rapidly developing research topics in recent years. As an excellent flexible material, fibre has unparalleled advantages in weaving and compatibility with the human body. Combining fibres with organic electrochemical transistors is a promising research direction that has the high sensitivity of organic electrochemical transistor testing and the human body compatibility and flexibility of wearable electronic products. This paper introduces the relevant operating principles, working modes and commonly used channel materials of organic electrochemical transistors. Based on the basic device structure of organic electrochemical transistors, the development and changes of organic electrochemical transistors in recent years are discussed, and the research results of fibre-based electrochemical transistors by researchers focusing on the application of fibre-based organic electrochemical transistors in chemical sensing, bio-sensing and other application explorations are summarized. Finally, this paper visioned the future development trend of fibre-based organic electrochemical transistors.

Sensors are the core part of intelligent smart textiles, and flexible sensors play an important role in wearable smart textiles because of their softness, bend ability and stretch ability, and excellent electrical properties. Based on the working principle of sensors, the research progress of flexible sensors for smart textiles in recent years is reviewed, and the sensing mechanism, sensing materials and application status of different sensors are introduced respectively; the main research directions of flexible sensors for smart textiles are summarized: physiological parameter detection, pressure detection and motion detection, and the applications of the three research directions are reviewed. On this basis, the problems of intelligent flexible sensors and their development prospects are pointed out.

With the rapid popularization of IOT applications, wearable devices have been widely used in many fields such as sports and health, entertainment and medical assistance. In addition to the early wearable form, more attachment and implantable wearable devices are constantly developed, and the development of these new wearable devices is largely due to the development of miniaturization antenna technology. This paper discusses the different realization methods and performance index requirements of wearable antenna, introduces the research situation of wearable antenna at home and abroad in recent years, and analyzes the development trend of wearable antenna.

Following the principle of “people-oriented”, we explore the user needs of smart clothing for the elderly and provide reference for the development of such clothing. The target consumers of smart clothing for the elderly are divided into two categories: The elderly and the young, and the needs of elderly users are investigated by means of literature analysis and interviews. The study showed that the needs of elderly users for senior smart clothing can be divided into five areas: Physiological, psychological, aesthetic, functional and consumer; the younger group is generally willing to buy senior smart clothing for the elderly and wants functional design to focus on physiological monitoring technology and aesthetic design to focus on loose fit design and dark shades of colour matching. The findings of the study will help companies to improve their design solutions and promote the healthy development of the senior clothing market.

Flexible wearable pressure sensors are widely used in health diagnosis, sports monitoring, rehabilitation medicine, entertainment, and other fields due to some factors such as the stretch ability, bendability, light weight, portability, and excellent electrical properties. In recent years, significant progress has been made in flexible pressure sensors, and a variety of flexible pressure sensors that able to measure health status have been applied to the pulse wave, movement, respiration, and electrocardiogram (ECG) detection. However, there are still many problems to be solved in the development of flexible pressure sensors. This article summarizes the development of flexible pressure sensors in recent years, from the working principle to the structural design of the flexible pressure sensors; designs to build a high-performance flexible pressure sensors; discusses the problems existing in current flexible pressure sensors and envisions the development trend of flexible pressure sensors in the future. Flexible pressure sensors with excellent flexibility, good biocompatibility, rapid response, high sensitivity, and multifunctional integration have shown a broad application prospects.