Skin: Thermomechanical BehaviorBEBCTropocollagenAamoleculeCollagenTropocollagenmolecule: 60-80% of dryThermal Shrinkageweight of fat-free skin18-30%ofthea:Intramolecularcross-linksvolume of dermisb:Intemolecularcross-linksInitial concentration ofcollagenThermal damageOJ。Aexp(-E. /RT)dtInDescription:Remaining concentration un-denatured collagenC(O)-C(0)2 =1-exp[-2(t)]Deg(t)C(O
Skin: Thermomechanical Behavior • 60-80% of dry weight of fat-free skin • 18-30% of the volume of dermis Collagen ( ) 0 (0) ( ) ln exp ( ) a C A E RT dt C = = − Initial concentration of collagen Remaining concentration un-denatured collagen Thermal damage Description: ( ) ( ) ( ) ( ) ( ) 0 1 exp 0 C C t Deg t t C − = = − −
Skin: Thermomechanical BehaviorBEBCNociceptorWarmthHaitreceptorPorereceptoHeatSourceStratumEpidermisEpidermiscorneumZBloodDermisperfusion0DermisHHypodermisHypodermisSweatSweatNervePressure TouchglanddiuctXJTUBiomedical Engineering & Biomechanics Center
H z r Stratum corneum Epidermis Dermis Hypodermis Heat Source Blood perfusion Nociceptor XJTU Biomedical Engineering & Biomechanics Center Skin: Thermomechanical Behavior
TASkin: Thermomechanical BehaviorBEBCThe skin is heated at the surface by a heat source with aconstant temperature, e.g.,in contact with a hot plate, whilethe bottom of the skin tissue is kept at body temperature.Thetemperature distribution in skin:dTZ2α7(0.)=T(-)+%TX8dzIz=0 tPh1pcZβ. sin[βm (z+ H/2)-KPCbm=1aB2mpcTo(z) is the initial temperature field in the tissueβ= m元/ H,m= 1,2,3
The skin is heated at the surface by a heat source with a constant temperature, e.g., in contact with a hot plate, while the bottom of the skin tissue is kept at body temperature. The temperature distribution in skin: T (z,t) = T0 (z) + 2a H T¥ - k dT0 (z) dz z=0 é ë ê ê ù û ú ú ´ b m sin b m (z + H 2) é ë ù û 1 ab m 2 + v b rb cb rc 1- e -ab m 2 t- v b rb c b rc æ t è ç ö ø ÷ m=1 ¥ å T0 (z) is the initial temperature field in the tissue b m = mp H ,m =1,2,3,. Skin: Thermomechanical Behavior
Skin: Thermomechanical BehaviorBEBCFor a given temperature history, the corresponding stress"laminated'distribution in theskin layer can be calculated as,AT+C(1I+V)" E,,ATdz+C,(1+v)E,ATzdz0,=E,"E,,ATzdz["E,,ATdz+C,(1+V)T+z(1+V,)Cwhere is in-plane stress (parallel to skin surface); E=E/(1-v?)=(1+v)a, E is Young's modulus, v is Poisson ratio, a is thermal expansioncoefficient, (C, C2, C,) are materials constants depending on the relativethickness of each layer of skin tissue, and j is layer number
For a given temperature history, the corresponding stress distribution in the ‘laminated’ skin layer can be calculated as Skin: Thermomechanical Behavior
Skin: Thermomechanical BehaviorBEBCVCRSDAPCINDEVERRNARTA/DBOARDLOWTEMPBATH1.Momitor2.Camera3.HeaterHIGHTEMPBATHStepper Motor5.OxygenBottleXSIOIN6.Flash Lamp7.Test ChamberLoad Cell8.9.Thenmo couples10.Valve1l.Silk Suture12.Themmostatically cortrolled he ater91011126Hydrothermaltensilesystem
Hydrothermal tensile system Skin: Thermomechanical Behavior