“Return to the Soil” Nanopaper Sensor Device for Hyperdense Sensor Networks

Abstract

A nanopaper sensor device that combines humidity sensing, wireless information transmission, and degradability has been fabricated using wood-derived nanopaper as the substrate and dielectric layers. The nanopaper shows excellent suitability for capacitor dielectric layers because of its high dielectric constant, insulating properties suitable for thin-film formation, and lamination properties. A wireless transmission circuit containing the nanopaper capacitor can transmit radio signals in the megahertz band, and the relative humidity change can be output as a change in the radio signal owing to the humidity sensitivity of the nanopaper capacitor. More than 95% of the total volume of the nanopaper sensor device decomposes in soil after 40 days. Because the nanopaper sensor device does not need to be recovered, it is expected to greatly contribute to a sustainable society through realization of hyperdense observation networks by mass installation of sensor devices.

Versatile Wood Cellulose for Biodegradable Electronics

“…(a), (b), (c), (d), (e), and (f) are reproduced with permission. [ 208 ] Copyright 2019, American Chemical Society.…”

Inherently Distinctive Potentialities and Uses of Nanocellulose Based on its Nanoarchitecture

“…Many attempts have been made to increase the humidity stability of nanocellulose materials by surface hydrophobization and preparation of composite structures (Ansari et al 2014). Contrary to such general concerns, a biodegradable humidity sensor has recently been proposed, which exploits the unique environmentally responsive moisture absorption property of nanocellulose (Kasuga et al 2019). Such unique strategy for materials design that positively uses the inherent hydrophilic properties of cellulose is required to expand the potential of nanocellulose beyond the replacement of conventional materials.…”

All-cellulose-derived humidity sensor prepared via direct laser writing of conductive and moisture-stable electrodes on TEMPO-oxidized cellulose paper

“…Because electrodes require sufficient electrical conductivity and stability against moisture, they are commonly made from noble metals, such as platinum, 7 gold, 8,9 and silver. 10,11 However, to meet the demand of the ''trillion sensor'' era, humidity sensors must be composed of abundant and renewable resources.…”

“…[13][14][15][16] In addition, the high density of hydrophilic groups in cellulose molecules makes them sensitive to water vapor, thus providing the ability to use cellulose as a humidity-sensing material. 11,[17][18][19][20] Various electrodes have been fabricated on cellulosic materials using different methods, 21 such as printing, 11 pasting, 20 painting, 22,23 and spraying, 24 for flexible and wearable humidity sensing. For example, a flexible humidity sensor comprising a 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized cellulose nanofiber as the sensing material and gold as the electrodes has been reported.…”

“…17 Degradable humidity sensors have also been developed using cellulose nanofiber paper as the sensing material and silver as the electrodes. 11 However, the use of non-renewable electrodes is still necessary to meet many requirements, such as having a sufficiently higher electrical conductivity than humiditysensing materials and stability against moisture, making it difficult to realize humidity sensors made from fully renewable materials.…”