DEFINE A GEOMETRY INSIDE THE SPHERE

Note: This is a follow-up of my old question: https://www.mathworks.com/matlabcentral/answers/questions/new/?s_tid=gn_mlc_ans_ask. The two questions is on the same project that I am working on, but in different

Dear Everyone,

I am working on a heat transfer model that shows the impact of laser beam on a small, spherical particle using PDEPE in Matlab. Diameter of the particle is around 60 um. The particle has a (few) neighboring particles, with a few assumptions:

• The contact area between particles have an average radius of 10% of the radius of the particle (6 um) - which made impact area around 28 um2.
• The neighboring particles has a constant, uniform temperature of 423 K.

I am thinking of using the thermalBC command, which define the contact area as a boundary condition:

 thermalBC(thermalmodel,'Face',2,'Temperature',423); %Face 1 is the face of sphere

So now what I cannot define is the contact area. Currently, I am using this to define the sphere:

gm = multisphere(3e-5);
thermalmodel.Geometry = gm;

Question: Is there any way I can define a "Face" geometry as the contact area?

Thank you everyone.