The “Heart of Voh”, immortalized by Yann Arthus Bertrand in his book "The Earth from the Air"depicts a sparse, heart-shaped clearing in the mangroves of New Caledonia. This highly poetic image is also the physical representation of thermal diffusion phenomena disrupted by fluid flow. This type of figure is a basic figure for analyzing source fields in a microfluidic channel surrounded by solid walls. Several analytical solutions will be presented and used for the estimation of crucial parameters related to the thermal diffusivity of the walls around the channel et the fluid flow inside the channel.