The design of a biomechanics prosthesis for right hand whose dimensions and weight allow its adaptation to children over 8 years and adolescents, is presented. Each finger is disposed in two sections, a fusion of the middle and distal phalanx, and a proximal phalanx articulated to the hand palm. The angles of the movement for the extension and flexion of all fingers, except the thumb, are controlled by a link located sideways. The drive system, which generates three degrees of freedom, is based on three linear actuators located in the palm, led by an Arduino microcontroller and activated by a voice recognition system to execute the cylindrical grasp's functions, the precision grasp, hook prehension and the extended index finger, is based on three linear actuators located on the palm, which have a reference potentiometer that provides its position, such indication is used by the microcontroller via the analogic input signal. To validate the design, a stresses and displacements analysis, and the determination of the safety factor that offers the device for the selected materials is carried out, using a computer program based on the Finite Element Method. The results obtained show a light prosthetic device that weights 200 grams, and can operate safely allowing four grip functions with the normal angles of the hand.