High-performance nanopattern triboelectric generator by block copolymer lithography

highlights

• Large-area nanopatterning is introduced on a flexible Au substrate by block copolymer lithography.

• We fabricate ultrahigh power energy harvesting nanogenerators based on contact-electrification principle exploiting the effective contact area enhancement by block copolymer lithography.

• This nanogenerator can generate remarkably high output voltage and current, which can directly light up 504 serially connected multicolored LEDs.

Abstract

Large-area nanopatterning is introduced on a flexible gold substrate by block copolymer (BCP) lithography. We fabricate ultrahigh power energy harvesting nanogenerators based on contact-electrification principle exploiting the effective contact area enhancement by block copolymer lithography. Owing to the facile and effective surface area enhancement by BCP nanopatterning, significant enhancement of triboelectric charge induction is attained. Output currents from TENG increased at least 16 times after BCP nanopatterning. This nanogenerator can generate remarkably high output voltage and current, which can directly light up 504 serially connected LEDs. The resultant nanogenerator attains the maximum instantaneous current of 1.6 mA and output power of 93.2 W/m². Electrical energy generated by single cycle of impact force is 0.54 mJ, and the average electrical energy is 114.89 mW. Those values indicate one of the highest device performance ever reported for the TENGs based on contact-separation mode thus far.

Introduction

A great deal of research efforts have been devoted for the effective harvest of ambient energy sources such as solar energy, wind, ocean waves, subtle mechanical vibration and so on. In particular, mechanical energy harvest using nanogenerators has attracted considerable research attention owing to the technological potential to realize a self-powered system. Several relevant technologies have been developed based on piezoelectric [1], [2], [3], [4], [5], thermoelectric [6], [7], [8], and triboelectric effects (contact-electrification) [9], [10], [11]. Among them, triboelectric nanogenerator (TENG) may offer a high power energy harvest through cost-effective simple device fabrication.

TENG generates electrical energy by means of two principles: contact-electrification [12], [13], [14] and electrostatic induction. Once two materials with different triboelectricity come into mechanical contact, charge transfer occurs at their interface. While the two materials separate, the electrostatic potential difference between the two materials enforces current flow through a load connected to an external device. Presently, enhancement of the output power of TENG is a crucial issue for various potential applications. In this regard, Wang et al. developed a variety of concepts of large-scale TENG, which incorporated metal nanoparticles [11], [15], [16], [17], a 3D stacked structural design [18], [19], [20], [21], organic polymer etching [22], [23], [24], [25], [26], [27] and various surface morphologies [11], [19], [20], [28], [29], [30], [31] in order to increase mechanical contact area.

Block copolymer (BCP) self-assembly offers lithographic nanotemplates for next-generation lithography as a result of the microphase separation of covalently linked incompatible polymer blocks [32], [33], [34]. More specifically, dense packing of self-assembled nanospheres or vertical cylinders in BCP thin films provides hexagonal nanopatterns with typical feature size ranging from 3 to 50 nm [35], [36]. Owing to the inherent scalability of self-assembly principle, well-ordered hexagonal nanopatterns can be readily produced over an arbitrary large area substrate. The resultant dramatic increase of surface area can be exploited for many different applications.

Herein, we present a high-performance large-area TENG with well-ordered hexagonal metal nanopatterns prepared by BCP nanolithography. The fabricated TENG generates a maximum output power of 233 mW and has an output power density of 93.2 W/m². We also demonstrate that the TENG can energize 504 commercial LED bulbs connected in a series at once. Owing to such a high efficiency, our nanopattern TENG can serve as a self-powered device to harvest subtle ambient energy sources, such as vibration energy, wave energy, and wind.