Liquid Metal‐Based Transient Circuits for Flexible and Recyclable Electronics

Abstract

Transient electronics, arising electronic devices with dissolvable or degradable features on demand, is still at an early stage of development due to the limited choices of materials and strategies. Herein, a facile fabrication method for transient circuits by the combination of room-temperature liquid metals (RTLMs) as the electronic circuit and water-soluble poly(vinyl alcohol) (PVA) as the packaging material is reported. The as-made transient circuits exhibit remarkable durability and stable electric performance upon bending and twisting, while possessing short transience times, owing to the excellent solubility of PVA substrates and the intrinsic flexibility of RTLM patterns. Moreover, the RTLM-based transient circuit shows an extremely high recycling efficiency, up to 96% of the employed RTLM can be recovered. As such, the economic and environmental viability of transient electronics increases substantially. To validate this concept, the surface patterning of RTLMs with complicated shapes is demonstrated, and a transient antenna is subsequently applied for passive near-field communication tag and a transient capacitive touch sensor. The application of the RTLM-based transient circuit for sequentially turning off an array of light-emitting-diode lamps is also demonstrated. The present RTLM-based PVA-encapsulated circuits substantially expand the scope of transient electronics toward flexible and recyclable transient systems.

Liquid Metal–Based Soft Microfluidics

“…Interestingly, by this approach, liquid metal can be recovered. For example, the transient circuit comprising of polyvinyl alcohol (PVA) as substrate and liquid metal Galinstan as electric conductor could be recovered after dissolution of the PVA in water by simply treating with sodium hydroxide solution, yielding in a recovery rate as high as 96% …”

“…j) Photographs showing the capacitive sensor integrated on a glove for slides presentation. Reproduced with permission . Copyright 2019, John Wiley and Sons.…”

“…For example, the transient circuit comprising of polyvinyl alcohol (PVA) as substrate and liquid metal Galinstan as electric conductor could be recovered after dissolution of the PVA in water by simply treating with sodium hydroxide solution, yielding in a recovery rate as high as 96%. [32] Although the oxide layer affects surface energy (SFT) of the liquid metal, gallium oxide is beneficial for the dispersion of LM into microdroplets. For example, liquid metal nanodroplets can be easily achieved by sonication of liquid metal in aqueous solution because the oxide layer prevents the liquid meal droplets from fusion.…”

“…Reproduced with permission. [32] Copyright 2019, John Wiley and Sons. k) LM integrates inside polymers for harvesting of mechanical energy from the human motion, resulting in powering of the wearable electronics such as pedometer and mini-calculator.…”

Liquid Metal Antennas: Materials, Fabrication and Applications

“…However, even these approaches suffer from irreversible deformation after certain bending cycles [1]. Alternatively, the liquid metals patterning methods are actively being researched for applications like stretchable and soft electronics [22,46,47]. A wide variety of LM patterning techniques for fabrication of general electronic circuits including microwave components were discussed in [48].…”