Functional device , in particular integrable into a trafficable pavement , comprising successively: - a first protective film , arranged on the front face of the device, made of a first material, - an internal encapsulation film , made of a third material, - a second protective film arranged on the rear face of the device, made of a fifth material, characterised in that said functional device further comprises: - a first external encapsulation film between the first protective film and the internal encapsulation film , the first external encapsulation film being made of a second material, - a second external encapsulation film between the internal encapsulation film and the second protective film , the second external encapsulation film being made of a fourth material, - one of the films, among the first external encapsulation film , the internal encapsulation film and the second external encapsulation film , coating active elements , the first material, the second material, the third material, the fourth material and the fifth material having Young's moduli E 1 , E 2 , E 3 , E 4 and E 5 , respectively, and coefficients of thermal expansion CTE 1 , CTE 2 , CTE 3 , CTE 4 and CTE 5 , respectively, E 1 and E 5 being similar or identical, E 2 and E 4 being similar or identical, E 1 > E 2 and E 4 < E 5 , CTE 1 and CTE 5 being similar or identical, CTE 2 and CTE 4 being similar or identical, CTE 1 < CTE 2 and CTE 4 >CTE 5 . - a first protective film , arranged on the front face of the device, made of a first material, - an internal encapsulation film , made of a third material, - a second protective film arranged on the rear face of the device, made of a fifth material, characterised in that said functional device further comprises: - a first external encapsulation film between the first protective film and the internal encapsulation film , the first external encapsulation film being made of a second material, - a second external encapsulation film between the internal encapsulation film and the second protective film , the second external encapsulation film being made of a fourth material, - one of the films, among the first external encapsulation film , the internal encapsulation film and the second external encapsulation film , coating active elements , - a first external encapsulation film between the first protective film and the internal encapsulation film , the first external encapsulation film being made of a second material, - a second external encapsulation film between the internal encapsulation film and the second protective film , the second external encapsulation film being made of a fourth material, - one of the films, among the first external encapsulation film , the internal encapsulation film and the second external encapsulation film , coating active elements , the first material, the second material, the third material, the fourth material and the fifth material having Young's moduli E 1 , E 2 , E 3 , E 4 and E 5 , respectively, and coefficients of thermal expansion CTE 1 , CTE 2 , CTE 3 , CTE 4 and CTE 5 , respectively, E 1 and E 5 being similar or identical, E 2 and E 4 being similar or identical, E 1 > E 2 and E 4 < E 5 , CTE 1 and CTE 5 being similar or identical, CTE 2 and CTE 4 being similar or identical, CTE 1 < CTE 2 and CTE 4 >CTE 5 . <EOS>