The United States Centers for Disease Control and Prevention (CDC) reported that in every 1,000 diabetic patients, 

the rate of lower extremity amputation  (LEA)  due to  complications  first appearing in the feet is 18.4%. However, 

LEA is preventable, and can be prevented and treated through therapeutic shoes or orthopedic insoles. Due to the 

differences in the individuality  of patients' feet,  mass-produced orthopedic insoles cannot adapt to every patient, 

so the use of additive manufacturing can solve this problem.

Recently, researchers at Kocaeli University in Turkey scanned the foot with a three-dimensional scanner, obtained a 

personalized insole model based on the foot model,  and used the fused deposition (FDM) process to manufacture 

a special insole for diabetic feet. The mechanical properties of the E-SUN polymer wire printed samples used in the 

FDM process and the traditional ethyl vinyl acetate (EVA) samples were tested, and the insoles printed by the FDM 

process and the traditional EVA insoles were not synchronized in the walking process  ( The finite element analysis 

and comparison of standing  position,  heel on the  ground,  flat sole,  standing position,  and heel off the ground) 

were carried out to optimize the  FDM  printing  process to ensure the biomechanical function of the diabetic foot 

insole under the FDM process.

Figure 1 Step-by-step additive manufacturing of insoles based on FDM process

Figure 2 Test results of mechanical properties of ethyl vinyl acetate (EVA) and additive manufacturing samples (filling 

density of 10-100% respectively), (A) hardness test results and (B) tensile strength test results

Mechanical performance experiments show that the tensile stress of each sample of 3D printing with different filling 

densities  varies  between  6.5 and 12.5 MPa.  The tensile  stress of EVA  foam is 2.1 MPa, which is lower than any 3D 

printed samples.

Figure 3 Finite element analysis (FEA) of each printed insole model and traditional EVA foam model in the gait phase
The finite element analysis results show that under the same external force, as the filling density of the insole model 

increases,  the material  displacement value  decreases at each gait stage,  while the equivalent stress increases.  The 

results  show  that  the insole  model  with a filling  density of 30% and the insole model of EVA foam have the same 

finite element  analysis  results,  thereby  ensuring  the  biomechanical function of the additive manufacturing insole.

The  cost  of  traditional  processing  insoles is  US$31.92,  and  the  processing  time is 15 hours. A pair of dedicated 

insoles  manufactured  by  fused  deposition  (FDM)  cost  US$6.88  and the processing time is 8 hours. This method 

greatly reduces the cost and time.