# Artificial-Hand Technology--Current State of Knowledge in Designing and Forecasting Changes
## 1 Introduction  
Biomimetics, a present trend in many scientific fields, has been known and used by engineers for many years [1; 2]. This term stands for imitating natural elements, techniques, and systems for the purpose of solving many human problems [3; 4]. Natural solutions, improved by thousands of years of evolution, were the inspiration for many inventions, where the most known, considered by [PERSON] and built by the [PERSON] brothers, was the first aeroplane, of which the wings' shape was based on that of birds [3]. There are many examples of such solutions: the Schmitt trigger, inspired by squids' neural impulse propagation, the Velcro mechanism, observed on woodland burs sticking onto dog fur, trains, form mimicking the kingfisher diving into water, or modern animal-move/shape robots [5; 6; 7; 8; 9; 10; 11; 12]. The most important solution, from this article's perspective, is contained in ourselves. The role of biomimicking the human hand, the most dextrous tool ever known, acquired special significance during the Second World War, when the number of amputees suddenly increased [13; 14]. To recover their functionality, simple nonelectrical prostheses were applied that allowed to perform a pinch grasp. Their mechanical construction was based on a hook attached to the wrist and a single wire linked between it and the back. Flexion of the arm pulled the wire, thereby moving the hook [15; 16; 17]. Subsequently, electrical human-shaped robotic hands started to appear, but this was in 1967, when such hands became commercially available and it was not until 1977 that they began to have medical importance [18]. Since then, the ongoing growth of automation and space exploration induced a rise of new applications for artificial hands: teleoperations. Hazardous, such as radioactive, chemical, or biological, environments, require to follow strict safety procedures, and a human presence in those areas is best avoided. This also applies to extravehicular activity (EVA) [19; 20; 21; 22]. To allow an operator to work with a mobile robotic hand, it should have a more humanlike range of moves, which means that bothpower and a precise grasp must be obtained. As proof, [23] showed that only 29 out of the 195 EVA tools could be used with a single hand. To that effect, we make distinction between a holding and an actuating hand. Dexterity improvement should go together with a natural shape and size for better visual feedback and inglove operations; as [24] rightly said, \"a human will find it easier to control a robot hand with functions like their own hand\". The end of the 20 th and 21 st centuries brought big technological progress. This applied to new materials, processing abilities, designing techniques, and the miniaturization of existing devices and methods [25; 26; 27]. New tactile sensors not only reduced dimensions, but are also elastic, which makes them easier to place [28; 29; 30], similarly to DC motors where, instead of the old ones, high-power density devices are used. Furthermore, artificial muscles like shape memory alloys (SMAs), twisted and coiled polymers (TCP), dielectric elastomers (DEA), and others are gaining popularity [31; 32; 33; 34; 35]. Whole actuators lead to the possibility of installing more of them in the palm or forehand, therefore increasing the number of degrees of freedom (DOF) [36; 37; 38]. According to the material and fabrication techniques, 3D printing is indisputably the most important innovation, as it makes prototyping and replacing parts much faster and cheaper [39; 40]. Nowadays, except for the well-known solutions described above, the importance of humanoid robots is increasing [20; 41; 42]. The upcoming exploration of Mars will need the help of robots with dextrous skills to build a base [43; 44]. However, Earth is a place where such robots would be the most appropriable. Demographic analysis, carried by Japan, showed that, by the middle of the 21 st century, about 30% of Japan's population will be over the age of 65.