SCIENTIFIC PAPER Manufacturing and finite element assessment of a novel pressure reducing insole for Diabetic Neuropathic patients A. Ghassemi • A. R. Mossayebi • N. Jamshidi • R. Naemi • M. T. Karimi Received: 2 May 2014 / Accepted: 2 December 2014 Ó Australasian College of Physical Scientists and Engineers in Medicine 2014 Abstract Diabetes is one of the metabolic diseases. Uncontrolled diabetes can lead to diabetic foot ulcers and if it was not treated would lead to amputation. Foot ulcers can be prevented by using suitable insoles which are made of appropriate material and geometrically designed by con- stituent layers. In this study, single-layer and three-layer insoles have been compared during static and dynamic loading. The selected materials were silicone gel (SG), plastazote foam (PLZ), polyfoam (PF) and ethyl vinyl acetate foam (EVA). Four single-layer and 18 combina- tions of three-layer insoles were selected. Materials behaviors were determined by using a uniaxial pressure test. The description of stress and strain is obtained by using the model of three dimensional nonlinear Finite Element Method (FEM). Then samples were tested by using commercially available plantar pressure measure- ment system. The FEM results showed that the SG and PLZ insoles are more appropriate compared to single-layer insoles. The combinations of PLZ, SG and EVA (from top to bottom) are recognized as the best between three-layer insoles. Also the best three-layer insole is more effective in promoting a favourable stress and strain distribution than single-layer insoles, especially in dynamic mode. Accord- ing to simulation results, three-layer insole decreases stress concentration by 9 %. Also experimental tests showed that using three-layer insole decreases plantar pressure by 63 % compared to barefoot condition bare foot. Keywords Insole  Diabetes  Single-layer  Three-layer insole  Hyper elastic  3D FEM Introduction Diabetes is one of the metabolic diseases when it combines with neuropathy, it could lead to foot ulcer that if not healed, it will cause amputation. Ulcers happen in plantar of foot that has the more pressures [1]. Using unsuitable foot ware would be one of the causes of ulcers and medical insole may be the best way in solving this problem [2]. In the first step for designing suitable footwear, the plantar pressure needs to be measured correctly. Distribu- tion of the plantar pressure is important. Plantar pressure can be measured by in-shoe pressure sensors or by pressure platform. In this filed, we can refer to the studies which were done by Abu-Faraj 1969 [3]. He measured plantar pressure of diabetic persons in statically mode by putting pressure- sensitive receptors in different parts of the insole. According to this research when a person stands on his own A. Ghassemi  A. R. Mossayebi Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Isfaha ¯n, Iran e-mail: a_ghassemi@pmc.iaun.ac.ir A. R. Mossayebi e-mail: alireza.mossayebi.researcher@gmail.com N. Jamshidi (&) Department of Biomedical Engineering, Faculty of Engineering, University of Isfahan, HezarJerib St., P.O. Box 81746-73441, Esfaha ¯n, Iran e-mail: nima_jamshidi@yahoo.com R. Naemi Faculty of Health Sciences, Science Centre, Leek Road, Stoke-on-Trent ST4 2DF, UK e-mail: r.naemi@staffs.ac.uk M. T. Karimi Musculoskeletal Research Centre, Isfahan University of Medical Sciences, Esfaha ¯n, Iran e-mail: mohammad.karimi.bioengineering@gmail.com 123 Australas Phys Eng Sci Med DOI 10.1007/s13246-014-0319-0