Mechanochromic\nChameleon Packaging Based on Polydiacetylene

We demonstrated a mechanochromic chameleon packaging\nthat quantitatively\nvisualizes damage based on the polydiacetylene blue-to-red color transition.\nThe applied pressures on the damage can be conveniently read by taking\na photograph via a homemade mobile app called the “Pressure\nAnalysis App”. The key aspects of the development were 1) the\nadjustment of the sensitivity by adding guest molecules into the PDA\nmatrix, 2) quantitative calibration, and 3) the accurate reading of\nthe pressure from RGB images based on the calibration. The force sensitivity\nof polydiacetylene on cellulose was characterized in the range of\n30–100 nN (2.59–8.86 MPa) at the nanoscale by dual friction\nforce/fluorescence microscopy, and in the range of 0.7–2.2\nN (0.11–0.35 MPa) at the macroscopic scale by a friction tester.\nThe scanning speed was found to be one of the key parameters, where\nthe force sensitivity above 50 mm/s was 6.45 times larger than that\nbelow 10 mm/s. The developed mechanochromic packaging system can be\nused for transporting electronics and medical tools, such as vaccine\nvials, food, etc., more safely and reliably in the future.