Polyurethane material for indicating pH at a locus, preferably as indication of presence of microbes, comprising a polyurethane network having immobilised therein one or more hydrophilic copolymers, the or each said copolymer comprising:
hydrophilic monomer; and

indicating monomer, which provides an indication in response to a change in hydrophilic state of said hydrophilic monomer and/or copolymer;

characterised in that the or each copolymer further comprises one or a plurality of ionisable groups or moieties or polymerisable monomers having one or more characteristic pKa values in the range 5 to 10 and which are responsive to pH at the locus in the range pH 5 to pH 10

and in that hydrophilic state of hydrophilic copolymer is dependent on ionisation of said ionisable groups, moieties or monomers; kit and device comprising the material and process for preparation thereof; and use in detecting or sensing microbes or pH.