Ronan Hinchet

Shape memory polymer-based self-healing triboelectric nanogenerator

Recently, triboelectric nanogenerators (TENGs) have received increasing interest due to their large potential for mechanical energy harvesting. Important progress has been achieved in increasing the output power and efficiency while new structures have emerged. In particular, their robustness and endurance have increased, but some critical concerns still remain about the degradation and lifetime of TENGs. How will TENGs age under intensive use in our daily lives? To address this issue, we propose in this paper to use shape memory polymers (SMPs) to extend TENGs’ lifetimes and guarantee their performance. For this purpose we introduce a new smart SMP-based self-healing TENG which has the capacity to be healed and to recover good performance after degradation of its triboelectric layer. We studied the degradation and healing process of the SMP–TENG, and the improvement in its endurance and lifetime, and thus demonstrate the huge potential of self-healing SMP–TENGs.

Recent Progress on Flexible Triboelectric Nanogenerators for SelfPowered Electronics.

Recently, smart systems have met with large success. At the origin of the internet of things, they are a key driving force for the development of wireless, sustainable, and independent autonomous smart systems. In this context, autonomy is critical, and despite all the progress that has been made in low-power electronics and batteries, energy harvesters are becoming increasingly important. Thus, harvesting mechanical energy is essential, as it is widespread and abundant in our daily life environment. Among harvesters, flexible triboelectric nanogenerators (TENGs) exhibit good performance, and they are easy to integrate, which makes them perfect candidates for many applications and, therefore, crucial to develop. In this review paper, we first introduce the fundamentals of TENGs, including their four basic operation modes. Then, we discuss the different improvement parameters. We review some progress made in terms of performance and integration that have been possible through the understanding of each operation mode and the development of innovative structures. Finally, we present the latest trends, structures, and materials in view of future improvements and applications.

Wearable and Implantable Mechanical Energy Harvesters for Self-Powered Biomedical Systems

In this issue of ACS Nano, Tang et al. investigate the ability of a triboelectric nanogenerator (TENG) to self-power a low-level laser cure system for osteogenesis by studying the efficiency of a bone remodeling laser treatment that is powered by a skin-patch-like TENG instead of a battery. We outline this field by highlighting the motivations for self-powered biomedical systems and by discussing recent progress in nanogenerators. We note the overlap between biomedical devices and TENGs and their dawning synergy, and we highlight key prospects for future developments. Biomedical systems should be more autonomous. This advance could improve their body integration and fields of action, leading to new medical diagnostics and treatments. However, future self-powered biomedical systems will need to be more flexible, biocompatible, and biodegradable. These advances hold the promise of enabling new smart autonomous biomedical systems and contributing significantly to the Internet of Things.

Control of Skin Potential by Triboelectrification with Ferroelectric Polymers.

Negatively polarized ferroelectric polymer β-P(VDF-TrFE) shows higher positive triboelectric properties than skin, which could lead to new medical applications. Kelvin force microscope measurements and triboelectric nanogenerator characterizations are performed to demonstrate this new property. In addition, how many negative charges are exchanged by contact electrification between the negatively polarized β-P(VDF-TrFE) and the skin is estimated.

Fully Stretchable Textile Triboelectric Nanogenerator with Knitted Fabric Structures

Harvesting human-motion energy for power-integrated wearable electronics could be a promising way to extend the battery-operation time of small low-power-consumption electronics such as various sensors. For this purpose, a fully stretchable triboelectric nanogenerator (S-TENG) that has been fabricated with knitted fabrics and has been integrated with the directly available materials and techniques of the textile industry is introduced. This device has been adapted to cloth movement and can generate electricity under compression and stretching. We investigated plain-, double-, and rib-fabric structures and analyzed their potentials for textile-based energy harvesting. The superior stretchable property of the rib-knitted fabric contributed to a dramatic enhancement of the triboelectric power-generation performance owing to the increased contact surface. The present study shows that, under stretching motions of up to 30%, the S-TENG generates a maximum voltage and a current of 23.50 V and 1.05 μA, respectively, depending on the fabric structures. Under compressions at 3.3 Hz, the S-TENG generated a constant average root-mean square power of up to 60 μW. The results of this work show the feasibility of a cloth-integrated and industrial-ready TENG for the harvesting of energy from human biomechanical movements in cloth and garments.

Research Update: Nanogenerators for self-powered autonomous wireless sensors

Largely distributed networks of sensors based on the small electronics have great potential for health care, safety, and environmental monitoring. However, in order to have a maintenance free and sustainable operation, such wireless sensors have to be self-powered. Among various energies present in our environment, mechanical energy is widespread and can be harvested for powering the sensors. Piezoelectric and triboelectric nanogenerators (NGs) have been recently introduced for mechanical energy harvesting. Here we introduce the architecture and operational modes of self-powered autonomous wireless sensors. Thereafter, we review the piezoelectric and triboelectric NGs focusing on their working mechanism, structures, strategies, and materials.

Rewritable ghost floating gates by tunnelling triboelectrification for two-dimensional electronics

Gates can electrostatically control charges inside two-dimensional materials. However, integrating independent gates typically requires depositing and patterning suitable insulators and conductors. Moreover, after manufacturing, gates are unchangeable. Here we introduce tunnelling triboelectrification for localizing electric charges in very close proximity of two-dimensional materials. As representative materials, we use chemical vapour deposition graphene deposited on a SiO2/Si substrate. The triboelectric charges, generated by friction with a Pt-coated atomic force microscope tip and injected through defects, are trapped at the air–SiO2 interface underneath graphene and act as ghost floating gates. Tunnelling triboelectrification uniquely permits to create, modify and destroy p and n regions at will with the spatial resolution of atomic force microscopes. As a proof of concept, we draw rewritable p/n+ and p/p+ junctions with resolutions as small as 200 nm. Our results open the way to time-variant two-dimensional electronics where conductors, p and n regions can be defined on demand.