Interposer with first and second adhesive layers

A flow cell comprising:

• a first substrate having a surface in which a plurality of wells are defined, wherein a biological probe is disposed in each of the wells;
• a second substrate;
• and
• an interposer disposed in-between the first substrate and the second substrate, the interposer comprising:
• a base layer having a first surface and a second surface opposite the first surface, the base layer comprising black polyethylene terephthalate (PET),
• a first adhesive layer bonding the first surface of the base layer to a surface of the first substrate, the first adhesive layer comprising acrylic adhesive, and
• a second adhesive layer bonding the second surface of the base layer to a surface of the second substrate, the second adhesive layer comprising acrylic adhesive, wherein:
• a plurality of microfluidic channels are disposed within the interposer, the plurality of microfluidic channels extending through each of the base layer, the first adhesive layer, and the second adhesive layer, the plurality of microfluidic channels being configured to deliver a fluid to the plurality of wells.