Peptides have attracted considerable attention due to their biocompatibility, functional molecular recognition and unique biological and electronic properties. The strong piezoelectricity in diphenylalanine peptide expands its technological potential as a smart material. However, its random and unswitchable polarization has been the roadblock to fulfilling its potential and hence the demonstration of a piezoelectric device remains lacking. Here we show the control of polarization with an electric field applied during the peptide self-assembly process. Uniform polarization is obtained in two opposite directions with an effective piezoelectric constant d₃₃ reaching 17.9 pm V⁻¹. We demonstrate the power generation with a peptide-based power generator that produces an open-circuit voltage of 1.4 V and a power density of 3.3 nW cm⁻². Devices enabled by peptides with controlled piezoelectricity provide a renewable and biocompatible energy source for biomedical applications and open up a portal to the next generation of multi-functional electronics compatible with human tissue.

Realization of a self-assembled, nontoxic and eco-friendly piezoelectric device with high-performance, sensitivity and reliability is highly desirable to complement conventional inorganic and polymer based materials. Hierarchically organized natural materials such as collagen have long been posited to exhibit electromechanical properties that could potentially be amplified via molecular engineering to produce technologically relevant piezoelectricity. Here, by using a simple, minimalistic, building block of collagen, we fabricate a peptide-based piezoelectric generator utilising a radically different helical arrangement of Phe-Phe-derived peptide, Pro-Phe-Phe and Hyp-Phe-Phe, based only on proteinogenic amino acids. The simple addition of a hydroxyl group increases the expected piezoelectric response by an order of magnitude (d₃₅ = 27 pm V⁻¹). The value is highest predicted to date in short natural peptides. We demonstrate tripeptide-based power generator that produces stable max current >50 nA and potential >1.2 V. Our results provide a promising device demonstration of computationally-guided molecular engineering of piezoelectricity in peptide nanotechnology.

Diphenylalanine (FF) represents the simplest peptide building block that self-assembles into ordered nanostructures with interesting physical properties. Among self-assembled peptide structures, FF nanotubes display notable stiffness and piezoelectric parameters (Young’s modulus =19-27 GPa, strain coefficient d33= 18 pC/N). Yet, inorganic alternatives remain the major materials of choice for many applications due to higher stiffness and piezoelectricity. Here, aiming to broaden the applications of the FF motif in materials chemistry, we designed three phenyl-rich dipeptides based on the β,β-diphenyl-Ala-OH (Dip) unit: Dip-Dip, cyclo-Dip-Dip, and tert-butyloxycarbonyl (Boc)-Dip-Dip. The doubled number of aromatic groups per unit, compared to FF, produced a dense aromatic zipper network with dramatically improved Young’s modulus of ~70 GPa which is comparable to aluminium. Piezoelectric strain coefficient d33 of ~73 pC/N of such assembly exceeds that of poled polyvinylidene-fluoride (PVDF) polymers and compares well to that of lead zirconium titanate (PZT) thin films and ribbons. The rationally-designed π-π assemblies show a voltage coefficient of 2-3 Vm/N, an order of magnitude higher than PVDF, improved thermal stability up to 360ºC (~60ºC higher than FF) and useful photoluminescence with wide-range excitation-dependent emission in the visible region. Our data demonstrate that aromatic groups improve the rigidity and piezoelectricity of organic self-assembled materials for numerous applications.