Liquid metal imbalance of the surface tension induces a pressure difference between the rear and the head, which produces a thrust to drive the droplet toward the head; at the same time, the hydrogen produced in the electrochemical reaction process also further raises the thrust. The discovery of this phenomenon laid the technical foundation for the development of intelligent motors, vascular robots, fluid pumping systems, flexible actuators and even more complex liquid metal robots. Liquid metal Liquid metal consists of alloys with very low melting points which form a eutectic that is liquid at room temperature. The standard metal used to be
Technical diving magazine was using the term "technical diving", as an analogy with the established term "technical (rock) climbing". In the US the Occupational Safety and Health Administration categorises diving which is not occupational as "recreational diving" for purposes of exemption from regulation. This is also the case in some other countries, including South Africa. There is some professional disagreement as to what exactly technical diving encompasses. Nitrox diving and rebreather diving were originally considered technical, but this is no longer universally the case as several certification agencies now offer Recreational Nitrox and recreational rebreather training and certification. Some training agencies classify