Wearable optical physiological monitoring device adhesion

An electronic device configured to monitor physiological signals of a user, the electronic device comprising:

• a housing at least partially enclosing a circuit board configured to process physiological signals to infer a physiological characteristic of the user;
• a flexible wing extending from the housing and configured to be affixed to a surface of the user;
• and
• an optical sensor assembly positioned on the flexible wing and configured to obtain a photoplethysmography signal, wherein the optical sensor assembly comprises an optical emitter configured to emit light and an optical detector configured to receive light, wherein at least a portion of the light emitted by the optical emitter is directed into the skin of the user and received by the optical detector from the skin of the user, wherein the optical sensor assembly further comprises a first directional layer between the optical emitter and the surface of the user and a second directional layer between the optical detector and the surface of the user, and wherein the first directional layer directs light from the optical emitter towards the surface of the user and the second directional layer directs light from the surface of the user towards the optical detector.