The properties associated with the fastest growth in CNT-related publications are brittleness and exergy. Prominent examples of the use of the term brittleness include reinforcing materials with CNTs to reduce their intrinsic brittleness, including hydrogels (primarily for use in sensors), poly(lactic acid) (PLA) 122 (enabling the use of this biodegradable polymer for mechanically demanding applications), epoxy resins, 123, 124 conjugated microporous polymer membranes, 125 and silica aerogels. Other examples of brittleness relate to the use of CNTs as replacements for brittle, traditional materials used in battery components and other applications. Brittleness also appears in the context of strain sensors which combine brittle materials and CNTs in composites, where cracking of the brittle material in response to strain improves the piezoresistive response, resulting in a higher gauge factor.