  Recently Guduru and coworkers have demonstrated with neat theory and
experiments that both increase of strength and of toughness are possible in the
contact of a rigid sphere with concentric single scale of waviness, against a
very soft material. The present note tries to answer the question of a
multiscale enhancement of adhesion, considering a Weierstrass series to
represent the multiscale roughness, and analytical results only are used. It is
concluded that the enhancement is bounded for low fractal dimensions but it can
happen, and possibly to very high values, whereas it is even unbounded for high
fractal dimensions, but it is also much less likely to occur, because of
separated contacts.
