Figure 5.

a) Illustration of a stretchable circuit with a surface‐mounted blue LED powered via stretchable Ag interconnects on a modulus‐graded elastomer fabricated with a pure Sylgard 184 island and two shoulders, consisting of 80% Ecoflex 00–30 and pure Ecoflex 00–30. b) Photograph of the elastic circuit while characterized by our tensile tester. The wrinkling of the electrodes guarantees electronic functionality while stretching up to λ = 1.5. c) Finite element simulation of the engineered elastomer substrate, illustrating the smooth strain transition between the island and the shoulder layers. d) All‐elastomer circuit board. A surface‐mounted microprocessor (ATTiny10) controls four LEDs. The nonstretchable SMD parts are placed on Sylgard 184 islands embedded in an Ecoflex 00–30 matrix. Imperceptible Cr/Ag form the metallic, stretchable interconnects. e) Photograph of the elastic circuit connected to our toy‐brick setup. The microcontroller drives the LEDs in predefined sequences (Video S1, Supporting Information). f) Strain distribution across the sophisticated elastomeric matrix simulated with a finite element model. Smooth strain transitions from the stiff islands to the soft surroundings prevent electrode failure.