The pioneering efforts of the engineering team of this project in characterising pain reception and transmission have resulted in a mathematical-physiological model with minimal number of parameters (i.e. five parameters). This model has been shown to give excellent results when tested in vitro with various concentrations of substances. The nonlinear model parameters can capture complex diffusion and transport phenomena. The goal of the project is to validate the model and identify its parameter values in awake post-operative patients who can give verbal feedback on pain level they experience during their stay in hospital by choosing scores between 1 (no pain) and 10 (extreme pain). No pain stimuli will be induced into the patient, since the pain is already present as post-operative side-effect. Standard protocols treat light pain (levels from 4 to 7) with light analgesics as paracetamol or diclofenac; whereas heavy pain (levels above 7) are treated with strong opioids as remifentanil. Our model can be used for impedance data measured non-invasively in the hand palm of the patient in parallel with the standard recordings during this treatment. This is a fundamental research part in launching a full-proof objective mathematical-physiological based model for pain level evaluation. The targeted end-result is to have an objective measurement of pain during anesthetised patients (not awake), which is clearly beyond the state of art.