We demonstrate that marine chitin nanofibrils are able to modulate the growth direction of two-dimensional Au nanocrystals from nanoribbons, nanokites to nanosheets. The mechanism investigation reveals that deacetylation and exfoliation of chitin nanofibrils are essential to template directional growth of Au nanocrystals. The tight adhesion of chitin nanofibrils on the Au surface enables the design of functional hybrids as ultrafast and ultrasensitive responsive devices for humidity and pressure. Interestingly, the humidity responsive device shows an abrupt increase in resistance of up to 3 orders of magnitude with a tiny variation of relative humidity from 62% RH to 63% RH, and was capable of precisely sensing speech. As a conductive filler, only 0.09 vol% gold nanoribbons are able to append to tissue paper with a sheet resistance of up to 220 Ω sq-1, which can be used as a frequently-used pressure-sensing device. These sensing hybrids are highly promising in smart clothing and electronic skins.