An example flow cell includes a substrate including depressions separated by interstitial regions; a polymeric hydrogel positioned within each of the depressions; a primer set attached to the polymeric hydrogel; and one of: a passivation component attached to the interstitial regions, or a passivation component attached to the polymeric hydrogel, or respective passivation components attached to each of the interstitial regions and the polymeric hydrogel.