FLOW CELLS

1 . A flow cell, comprising:

a substrate;

a plurality of reactive regions spatially separated from one another across the substrate, each of the plurality of reactive regions including:

a polymeric hydrogel layer; and

a reactive entity attached to the polymeric hydrogel layer; and

a plurality of independently removable coatings respectively positioned over each of the plurality of reactive regions.

2 . The flow cell as defined in claim 1 , wherein at least one of the plurality of independently removable coatings has a different removal characteristic than at least one other of the plurality of independently removable coatings.

3 . The flow cell as defined in claim 2 , wherein each of the plurality of independently removable coatings has a different removal characteristic than each other of the plurality of independently removable coatings.

4 . The flow cell as defined in claim 3 , wherein the removal characteristic is solubility.

5 . The flow cell as defined in claim 1 , wherein the reactive entity in each of the plurality of reactive regions is a primer set.

6 . The flow cell as defined in claim 5 , wherein the primer set is the same in each of the plurality of reactive regions.

7 . The flow cell as defined in claim 5 , wherein the primer set of at least one of the plurality of reactive regions is different than the primer set of at least one other of the plurality of reactive regions.

8 . The flow cell as defined in claim 1 , wherein:

at least one of the plurality of independently removable coatings includes a plurality of sub-layers; and

the plurality of sub-layers defines a removal characteristic of the at least one of the plurality of independently removable coatings.

9 . The flow cell as defined in claim 1 , wherein the reactive entity in each of the plurality of reactive regions is an enzyme tag.

10 . The flow cell as defined in claim 1 , wherein each of the plurality of removable coatings has a different thickness.

11 . The flow cell as defined in claim 1 , wherein:

the substrate includes a plurality of depressions;

each of the plurality of reactive regions is positioned within a respective one of the plurality of depressions; and

each of the independently removable coatings is a photo-cleavable protective layer.

12 . The flow cell as defined in claim 11 , wherein the photo-cleavable protective layer is a hydrophilic polymer cross-linked with a photo-cleavable cross-linker or an acid-labile cross-linker.

13 . The flow cell as defined in claim 11 , wherein the photo-cleavable protective layer is a hydrophilic polymer capped with a photo-cleavable hydrophobic group or an acid-labile group.

14 . A method, comprising:

selectively removing at least one of a plurality of independently removable coatings respectively positioned over each of a plurality of reactive regions spatially separated from one another across a substrate, thereby exposing at least one of the plurality of reactive regions and a reactive entity at the at least one of the plurality of reactive regions, whereby at least one other of the independently removable coatings remains unaffected; and

initiating a reaction involving the reactive entity.

15 . The method as defined in claim 14 , wherein selectively removing the at least one of the plurality of independently removable coatings involves exposing the plurality of independently removable coatings to a predetermined solvent that dissolves the at least one of the plurality of independently removable coatings and does not dissolve the at least one other of the independently removable coatings.

16 . The method as defined in claim 14 , wherein:

the at least one of the plurality of independently removable coatings includes a plurality of sub-layers; and

selectively removing the at least one of the plurality of independently removable coatings involves exposing the at least one of the plurality of independently removable coatings to a sequential removal treatment that sequentially dissolves each of the plurality of sub-layers.

17 . The method as defined in claim 14 , wherein:

each of the plurality of removable coatings has a different thickness; and

selectively removing the at least one of the plurality of independently removable coatings involves exposing the plurality of independently removable coatings to a solvent for a predetermined time.

18 . The method as defined in claim 14 , wherein selectively removing the at least one of the plurality of independently removable coatings involves exposing the at least one of the plurality of independently removable coatings to light without exposing the at least one other of the independently removable coatings to the light, thereby photo-cleaving the at least one of the plurality of independently removable coatings.

19 . A digital fluidics cartridge, comprising:

a laminate film;

a resin positioned on the laminate film, the resin patterned with a plurality of spatially separated reactive regions;

a lid attached to a bonding region of the resin;

a fluid channel defined between the lid and the resin; and

a ground electrode positioned on a surface of the lid that faces the fluid channel.

20 . A digital fluidics system, comprising:

a digital fluidics instrument including a plurality individually addressable control electrodes; and

a digital fluidics cartridge, including:

a laminate film to be positioned in operative communication with the plurality individually addressable control electrodes;

a resin positioned on the laminate film, the resin patterned with a plurality of spatially separated reactive regions that are to be respectively aligned with the plurality individually addressable control electrodes;

a lid attached to a bonding region of the resin;

a fluid channel defined between the lid and the resin; and

a ground electrode positioned on a surface of the lid that faces the fluid channel.