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.

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Energy harvesting with piezoelectric nanomaterials spurred the development of self-powered nanosystems, and piezoelectric biomaterials are expected to play an important role in the biomedical field. Bio-inspired piezoelectric diphenylalanine (FF) peptide microstructures were fabricated on various substrates through anovel epitaxial growth approach. The low-temperature process produced vertically aligned FF peptidemicrorods with hexagonally arranged nanochannels and uniform polarization. Direct measurement of the piezoelectricity was achieved for the first time from a solidFF peptide single crystal and yielded an effective piezoelectric coefficient 33 at9.9 pm/V.The dense and aligned FF peptidemicrorods are advantageous for energy and sensing applications.

Strain-induced polarization charges in a piezoelectric semiconductor effectively modulate the band structure near the interface and charge carrier transport. Fundamental investigation of the piezotronic effect has attracted broad interest, and various sensing applications have been demonstrated. This brief review discusses the fundamentals of the piezotronic effect, followed by a review highlighting important applications for strain sensors, pressure sensors, chemical sensors, photodetectors, humidity sensors and temperature sensors. Finally, the review offers some perspectives and outlook for this new field of multi-functional sensing enabled by the piezotronic effect.

With the rapid development of portable electronics, exploring sustainable power sources is becoming more and more urgent. Utilizing a nanogenerator to harvest ambient mechanical energy could be an effective approach to solve this challenge. In this work, a novel spring-assisted hybrid nanogenerator (HG) consisting of a triboelectric nanogenerator (TENG) and an electromagnetic generator (EMG) was developed for harvesting low-frequency vibration energy. The results show that the TENG with a PTFE surface nanostructure has better output performance than that without the nanostructure. The effect of operating frequency on the open-circuit voltage and short-circuit current of the TENG and EMG is systematically investigated. Under a 2 Hz operating frequency, the EMG and TENG are able to produce a peak power of about 57.6 mW with a resistive load of 2000 Ω and 1682 μW with a resistive load of 50 MΩ, respectively. The impedance matching between the TENG and EMG can be realized by using a transformer to reduce the impedance of the TENG. The charging performance of the HG is much better than that of the individual EMG or TENG. The HG enabled us to develop a self-powered safety system and to power LEDs, and drive some electronic devices. The present work provides a superior solution to improve the output performance of the HG for harvesting low-frequency vibration energy.