How did the researchers switch on a strong piezoelectric response in the peptide material?

The correct answer is by adding one per cent of a suitable co-solvent. The team found that in water the peptide molecules form nanofibers and show no piezoelectric response. Introducing just that small share of a co-solvent reorganised the molecules into a highly ordered supramolecular arrangement, and the piezoelectric response switched on at once. Option A is precisely what the study did not do, and the release stresses the point: the chemical composition of the peptide was left untouched, and the key lay in controlling how the molecules assemble rather than in altering the molecule. Option C would defeat the purpose, since the aim was to replace brittle ceramics with a soft, biocompatible material. Option D is invented. The physical reason for the switch is worth remembering: controlled chiral self-assembly aligns molecular dipoles into a non-centrosymmetric structure, the basic condition for piezoelectricity.