As automatic devices with artificial intelligence, robots have been more and more involved in people's daily lives and have replaced human to perform related work in hazardous industries such as high temperature, high pressure, explosive disposal, etc. By the integration of various sensors, the existing robot systems already have achieved a lot of human sensations, like vision, hearing and olfaction. However, the robot systems are faced with one of the most challenging problems all the time: how to get sensitive tactile sensation like human beings. The birth of electronic skin will bring the robot systems tremendous changes and will enable the robots to get more information from the external environment.
Since the University of Tokyo first suggested an electronic artificial skin using organic field-effect transistors (hereafter referred to as OFET electronic skin), some research groups in Japan and America have constructed the electronic skin based on organic field effect transistor, capacitive electronic skin as well as piezoresistive electronic skin successfully. However, the application ranges of these devices are limited due to complicated processing technic and device structures, bigger driving voltage, lower sensitivity or characteristics such as non-transparency and non-flexibility resulting from the use of rigid silicon-based materials. Therefore, it is necessary to provide an artificial electronic skin which has simple structure, high sensitivity, high accuracy and durability.
Along with the advent of conceptual products such as the GOOGLE GLASS (a trademark), the APPLE IWATCH (a trademark), and the like, wearable equipment comes to public attention with advantages such as high sensitivity, low cost, low power consumption, easy portability, more convenient user experience, and so on, extending functions that a personal computer (PC) and cell phone do not have. By the deep integration with software and hardware technology and by means of highly integrated intelligent terminal, wearable equipment not only creates smart personal life, but also builds smart city and even smart world, thereby bringing the life-style and consumption concept of human being revolutionary changes. There will be many varieties of wearable equipment in future, but all of which will be combined with sensor technology, taking the human body as a part of input or output process, then connecting the Internet by itself or by applications (APP) on the cell phone, and finally achieving intelligent human-machine interaction.
The electronic skin with nanostructure, ultrathin thickness, lighter weight, and flexibility similar to human skin is the most suitable material for constructing wearable equipment. Recently, the world-recognized top journal Nature has reported an ultrathin (2 μm) electronic skin with organic field-effect transistors (OFET) structure, which is lighter than feather and still works after being kneaded, stretched out, or drawn back. However, because of low carrier mobility of organic field-effect transistors (OFET) the electronic skin needs high working voltage and high power consumption, but has low sensitivity.
In addition, with the rapid development of communication technology and continuous progress of computer science and technology, speech recognition becomes a remarkable high-tech intelligent human-computer interaction technology, which involves multi-disciplines comprehensive technologies of phonetics, vocalism principle, microelectronic technology, computer information processing technology, speech processing technology, circuit and system, sense technology, and so on. The application thereof has become a competitive new high-technology industry.
The reported speech recognition technologies are usually based on methods of speech template, large vocabulary continuous speech recognition, acoustic model, etc. However, these traditional speech recognition technologies have lots of problems. For example, in circumstances of noisy environment, unclear pronunciation with accent or in dialect, or of a multitude of voices from multi-people at the same time, voice input will have a bad effect, low recognition rate and even will fail to be recognized. The main reason for these problems mentioned above is that traditional voice acquisition modules capture voices by collecting transmitted signals of voices in the air, while other acoustic sources around will interfere the collecting of voice data.
Moreover, in order to extract physiological and pathological information from the pulse waves of human body as the basis for clinical diagnose and treatment, a number of pulse monitors appear in recent years, such as portable electronic sphygmomanometer which can measure pulse. However, this kind of portable electronic sphygmomanometers use mini air pump to pressurize rubber pneumatic bag and need pressurizing process and depressurizing process in every single measurement, thereby having some problems, such as big size, uncomfortable user experience during pressurization and depressurization, low accuracy in the detection of pulse, disability of displaying a full waveform of pulse wave, etc. Some large sphygmographes, such as the COMPLIOR (a trademark) analyzer (France), have accurate measuring results and good repeatability, but are mainly used in specialist treatment and the study of epidemiology and are too expensive to use in household or popular portable medical services.
Furthermore, in order to meet the growing needs of people, it is very necessary to explore new applications in various fields for the electronic skin which is an electronic device with extremely high sensitivity.