A　simple　thermal　aptasensing　platform　was　devised　for　the　sensitive　detection　of　organophosphate　pesticides　(using　malathion　as　a　model　target)　based　on　the　efficient　self-heating　reaction　of　a　warming　pad　with　a　switchable　target　responsive　enzyme-encapsulated　three-dimensional　(3D)　DNA　hydrogel　using　a　portable　thermometer　as　a　signal　readout　in　this　work.　The　existence　of　the　target　malathion　would　open　the　catalase-3D　network　and　lots　of　catalase　was　released　from　the　hydrogel,　which　could　efficiently　convert　H2O2to　an　O2molecule.　The　product　O2is　the　critical　condition　for　the　self-heating　of　the　warming　pad.　Thereafter,　the　temperature　was　enhanced　with　the　increasing　amount　of　O2.　The　strategy　displays　outstanding　specificity,　reproducibility　and　stability.　Moreover,　this　method　can　be　easily　extended　to　monitor　other　molecules　using　different　aptamer　sequences　in　practical　applications.　©　The　Royal　Society　of　Chemistry　2021.