Chemical sensor having a flexible member with III/N heterojunction

A chemical sensor comprising:

• a flexible membrane comprising a III/N heterojunction structure configured so as to form a two dimensional electron gas within said structure, the flexible membrane being free-standing over a supporting substrate;
• and
• a sensing material sensitive to one or more target chemicals;
• configured such that a change in stress within the heterojunction structure would modulate the resistivity of the two dimensional electron gas;
• wherein the sensing material is a layer of material different from the substrate which is disposed on at least part of said flexible membrane;
• and the sensing material would undergo a change in physical properties in the presence of said one or more target chemicals and would impart a change in stress within the heterojunction structure,
• wherein the change in physical properties of the sensing material is a volume change due to absorption of the one or more target chemicals or a change in structure or amount of the sensing material due to dissolution, absorption, or both absorption and dissolution of the sensing material in the presence of the one or more target chemicals.