A technique for producing a device for sensing a target species, comprising: providing first end second components, each comprising a support film, wherein at least one of said first and second components comprises at least one working electrode supported on the respective support film, at least one of said first and second components comprises at least one counter electrode supported on the respective support film, at least one of said first and second components defines a containing barrier supported on the respective support film, and at least one of said first and second components comprises an array of spacer structures supported on the respective support film; depositing a volume of liquid electrolyte on said first component; laminating said second component to said first component so as to spread said volume of liquid electrolyte out in a space created by said array of spacer structures within a liquid electrolyte area bounded by said containing barrier; wherein said liquid electrolyte functions to transport at least one electrochemical reaction product of an electrochemical reaction of the target species at the working electrode to the counter electrode for a counter electrochemical reaction at the counter electrode.