A novel SMA-based micro tactile display device for elasticity range of human soft tissues: Design and simulation

A novel micro tactile display device to display the elasticity of human soft tissues is presented in this paper. The device consists of 16 units in the form of a 4 × 4 units array. Each unit consists of two substrates separated by a 1.75 mm spacer. The first substrate holds a stiffness display pin (1 mm × 1 mm) which is supported by two Shape Memory Alloy (SMA) springs in parallel to provide tunable stiffness. A strain gauge on top of this substrate is used to measure the force applied on that pin. The other substrate includes a planar coil forming a non-contact eddy current sensor that is used to measure the deflection of the pin when subjected to an external force. Both the strain gauge and the eddy current sensors provide feedback signals that are used for characterization and control of the stiffness. Finite element simulation shows that the stiffness range of the designed device matches the range of elasticity of human soft tissues and the eddy current sensor detects up to 1.75 mm deflection which is suitable for characterization purposes. The simulation also studies the cross talk that possibly happen among the eddy current sensors due to the magnetic field.