An infrared sensor with at least one cantilever beam functionalized with chitin, chitosan or their derivatives that can be tailored to be sensitive to certain IR bands for detection and does not require cooling is described. The functional layers expand differently than the structural layer of the cantilever beam causing the beam to bend in response to exposure to infrared radiation. The sensor can be adapted to optical, piezoresistive, capacitive and piezoelectric methods of detect beam deflection. Sensitivity can be increased with a reflective layer to increase the absorption of infrared radiation by the functional layer.