2. Comparison of the Fabrication Method and Piezoelectric Coefficients of Piezoelectric Amino Acids and Their Derivatives.

Type	Materials	Morphology	Fabrication Method	Piezoelectric Coefficients (pm V–1)	Measurement/Calculation Method	Ref
Amino acids and their derivatives	β-glycine	Needle-like crystals	Drop casting	178 (d16)	DFT calculations and resonance testing
	β-glycine	Nanocrystalline films	Electrospray deposition	11.2 (d33)	PFM and quasi-static method
	β-glycine	Isolated crystals	Inkjet printing	2–4 (d33)	PFM
	β-glycine-PVP	Nanocomposite films	Aerosol printing	10.8 (d33)	PFM and quasi-static method
	β-glycine-PVA	Nanofibers	Electrospinning	4.2 (deff)	PFM
	γ-glycine	Single crystals	Drop casting	10.4 (d33)	DFT calculations and quasi-static method
	γ-glycine-PVA	Sandwich films	Solution casting (Hydrogen bonding heterostructure)	5.3 (d33)	Quasi-static method
	dl-alanine	Single crystals	Drop casting (Racemic coassembly)	10.3 (d33)	DFT calculations and PFM
	dl-alanine	Polycrystalline aggregate films	Drop casting (Racemic coassembly)	4.1 (d33)	Quasi-static method
	Isoleucine	Polycrystalline aggregate films	Mechanical annealing	1.2 (d33)	Quasi-static method
	Valine	Sheet arrays	PVD	11.4 (d33)	DFT calculations and PFM
	L-AcW	Single crystals	Drop casting (Molecular modifications)	47.3 (d25)	DFT calculations
	BPA/Ac-l-Ala	Single crystals	Drop casting (Co-assembly)	26.3 (d14)	DFT calculations
	BPA/Ac-d-Ala	Single crystals	Drop casting (Co-assembly)	21.9 (d14)	DFT calculations