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2024/5/22

環境発電型オールインワン
IoT の実装研究②-高性能創電・センサ機能の実装開発電力中央研究所 EX研究本部

小野新平

2024

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IoT普及へ向けた課題
１）キラーアプリがない
IoT導入を促進するキラーアプリが未だない。
２）ニーズとシーズのミスマッチ
IoT導入を検討している事業者のニーズ（機能、コストなど）と、IoT開発を行う側（高機能、高性能）との間にミスマッチがある。
３）環境発電技術の必要性が不明
メンテナンスフリーのメリットがあるが、コストが高く「一次電池で良い」と言われてしまう。
４）消費電力が大きい
通信やデータ処理をセンサで行うためには、より大きい電源を必要とする。

これらの課題を解決することでIoT普及の促進を！！
2024

2024/5/22

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o+ashi et al., Science 376, 502–507 (2022)

tal uncertainty, between the diffusion crossover point and the zero-sensing concentration
is notable and supports the theory that themore-mobile and less-hindered ions determine the sign of the voltage response.
This differential effect is not explained byDarcy’s continuum flow theory, which assumes that all molecules are carried at thesame speed as the solvent. Given that the flow
within the hydrogels is in a transition regime,
it should not be surprising that interaction
with the backbone leads to differential ion
transport rates and currents. We propose amechanistic picture of piezoionic electromechanical response in hydrogels with two mobileions, where the cations and anions do not
move at the same speed as the solvent, leading
to current and voltage generation. The mobileions are subject to a hydrodynamic drag force
from the convection of electrolyte within thepores. This is balanced by interactions withthe stationary polymer that hinder transport.
If the effective mobilities of the ions within thematrix, as inferred by diffusion coefficients D+
for cations and D− for anions, are the same as
they would be without the additional drag dueo−we expect that no voltage would be generated,as both ions are carried at the speed of thefluid, nf . Additionally, if cations and anions areequally hindered by the polymer, we expectthat no sense voltage would be generated.
These expectations lead to a predicted piezoionic coefficient that is proportional to thedifference in the two diffusion coefficients,hi
Dþ
D"a ¼ " eNksh Doþ " Do" (see the supplementary

本開発提案のポイント ①
materials for derivation). Here, e is the electronic charge (in coulombs), N is the concentration (per cubic meter), k is the matrix
permeability (in square meters), and h is thefluid viscosity (in pascal seconds). The relationship suggests that when the diffusion coefficients of the two ions are approximately
equal, the voltage generation will be zero (Fig.
2, G and H). It also suggests that by maximizing difference in ion size (and thereby
drag due to the matrix), a larger sense voltage
will be obtained. The use of bulk solution
values for Do+ and Do− is a starting point but
does not provide a quantitative match between experiment and theory because thepolymer affects the interactions between ions

生体は高度なイオン制御を行っている

生体はイオンの機能を最大活用

Fig. 1. Schematic representation comparing biological sensory transduction and piezoionics, andconceptual depiction of a piezoionic sensing device as an iontronic neuroprosthetic. (A) Mechanoreceptors
have anchors that attach the membrane to the extracellular matrix as well as a cytoskeleton that both stretch
an ion channel, causing an influx of sodium ions upon deformation. Once the cell membrane potential increases,
voltage-sensitive ion channels (not shown) open to allow reversal to resting potential. The rapid- and slow-adapting
mechanoreceptors differ, in part, in the mechanical structures of the cell. (B) Piezoionic skin assembly has abuilt-in potential difference set by the difference in fixed charge concentration between poly(acrylic acid) (polyAA;charged) and polyacrylamide (pAAM; neutral). Compression of the charged side creates a flux of solvent andprotons that increases this potential difference.

Y. Dobashi et. al.,Science (2022)

Downloaded from https://www.science.org at Yokohama National University Library on April 16, 2023

plementary materials.
he streaming potentials that generate theponses plotted in Fig. 2B are reliant oning a single mobile charge within the elecyte, balanced by a fixed charge of opposite
n on the polymer matrix. However, recentults (18–22) show that voltages are generd even in the absence of fixed charge. This
ect is confirmed in an uncharged polyylamide (pAAm) hydrogel swollen with 0.5 M aqueous sodium chloride, whose peak
se voltage and ionic conductivity both moonically increase as a function of concentran (Fig. 2E). No model has been developed
explain this response. The most straightward conclusion is that the chloride ionsplace faster than the sodium ions underentation. This could be due to several efs: filtration resulting from size differences
ween ions (23), differential affinity to thetrix, or fluidic hindrance effects in which
size is comparable to boundary layer dinsion (24). Given that pore sizes in the hygels are within a factor of 10 of solvatedsizes, and that filtration of potassium andoride is evident even in pAAm hydrogels
h low polymer content (23), we hypotheed that the physical barrier to diffusion
vided by the polymer matrix is a factor thatuences the generation of net current.
o observe the relationship between ionicbilities and piezoionic response, experints were conducted in poly(vinylideneoride-co-hexafluoropropylene) (PVDF-HFP)
d polymer electrolyte swollen with 0.1 toM lithium bis(trifluoromethanesulfonyl)de (LiTFSI) in propylene carbonate (PC).
e salt was chosen because the lithium andorine enable diffusion coefficients to be
dily extracted by nuclear magnetic resonce (NMR) (see supplementary materials).
salt concentration increases, there is also
eduction in the solvation shell and hydronamic radius of the lithium ion, from ardination number of four in its first shell
dilute concentrations down to two PC molles at high concentrations (25). This retion is apparent in the increase in lithium
usion coefficient with concentration, andtive to TFSI−, as shown in Fig. 2G. The retion occurs despite increasing solution visity (fig. S17). The diffusion coefficients oftwo ions cross over, with TFSI− dominant
ow concentrations and Li+ at high concentions. There is a corresponding polarity
t in the piezoionic voltage. The amplitude
d sign of the sensor response to a sinusoidal
entation (0.1 Hz, 5% compressive strain)
shown in Fig. 2H (based on data plotted in
S13, A to H). The voltage is positive at low
centrations but crosses over to negative
arity between 1.5 and 2.0 M—the samege in which diffusion coefficients cross

現時点では応用先が限定

batteries

Capacitors

生体のイオン制御技術を模倣（バイオミメティック）
蓄電池、振動発電素子、センサ、回路技術を開発
2024
2024/5/22

29 April 2022

2 of 63本開発提案のポイント ②
完全自律制御（周りに頼らない）IoT機器の社会実装
アイディア：先進基盤技術（基盤塗布型蓄電池・振動発電素子・無電源センサ・超低消費電力回路）を相互補完融合

材料科学、電気化学、電子工学、機械工学をまたぐ、新たな融合分野「スマートメカトロニクス」を利用してIoT機器の社会実装を目指す
JST戦略的創造研究推進事業「微小エネルギーを利用した革新的な環境発電技術の開発」

インフラから発生する低周波かつ広帯域の振動から発電・整流・蓄電・センサまでを一体化して行う完全自律型オールインワンIoT機器を実証することを目的とする。
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本開発提案のねらい
発電素⼦、センサ、回路、蓄電池のオールインパッケージ化
振動発電素⼦

ナノワット
電源管理回路

イオンセンサ

1.3mm

1us100us補
償500us1ms補償

10ms100ms補償

l 低周波振動⾮共振系 (数〜10 Hz)l ⾼効率発電(1回の接触あたり5 uC/cm2) 以上

l イオンの交差相関現象を利⽤したセンサ
l 超低消費電⼒を実現

l インピーダンス整合
l 超低消費電⼒（10 nW以下）

1つの基板に集積（オールインワン化）

⽣体模倣より超⾼効率、低消費電⼒を実現

5まとめと課題• 様々な分野の融合からIoT機器の社会実装を！！
一点突破型ではなく、他分野からの視点・技術（スマートメカトロニクス）を相互補完的に導入し、社会実装へ向けて研究開発、課題解決を加速• 生体に学ぶ低消費電力センサ、回路などの導入
バイオミメティック（生体模倣）の概念を導入し、極低消費電力センサを実現
発電・整流・蓄電・センサまでを一体化して行う完全自律型
オールインワンIoT機器の実現へ
連絡先：shimpei.ono.b7@tohoku.ac.jp
20242024/5/22(東北大学)
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