Finite Element Analysis of epidermal ridges in tactile sensing application

Human mechanoreceptors are the biological tactile transducers, providing tactile information to the somatosensory system. A biologically inspired tactile sensor replicates structural and design of the human fingertip to produce similar response to the human mechanoreceptors. The study of different shapes and heights of an artificial epidermal ridge is proposed in order to obtain the optimum design of a bio-inspired tactile sensor. The Finite Element Analysis model was conducted using COMSOL software. The artificial skin was modelled as a nearly compressible, linear hyperelastic material. There were five different shapes of the epidermal ridge which are the centered circle, centered square, centered rectangle, semi-circular and rectangular ridge each with six different heights. The heights of epidermal ridges tested are 100, 110, 150, 170, 210, 250 μm. A boundary load of 1 N/m² was applied on the top surface of the protrusion in z and x direction for normal and shear stress. The base of the model was constraint to maintain the same boundary conditions throughout all simulation. Simulations were done to determine the suitable depth for sensor placement in the skin area under the epidermal ridge. The simulated result for all different shape and height were compared. Simulation results with areas that experienced the highest stress were given to validate the proposed epidermal ridge model. The best epidermal ridge identified is the semi-circular model with 210 μm height with the value of 0.8246 N/m² simulated Von Mises stress distribution. The optimum sensor placement with cut line 3D is at 400 μm below the model top surface. The proposed artificial epidermal ridge finger skin with optimum shape and height of the epidermal ridge are readily applicable to be fabricated as a bio-inspired tactile sensor.