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Publisher DOI: 10.1002/adma.202105923
Title: Wafer-scale electroactive nanoporous silicon : large and fully reversible electrochemo-mechanical actuation in aqueous electrolytes
Language: English
Authors: Brinker, Manuel  
Huber, Patrick  
Keywords: actuorics; cyclic voltammetry; electrochemical characterization; laser cantilever bending; nanoporous media
Issue Date: Jan-2022
Publisher: Wiley-VCH
Source: Advanced Materials 34 (1): 2105923 (2022-01-06)
Abstract (english): 
Nanoporosity in silicon results in interface-dominated mechanics, fluidics, and photonics that are often superior to the ones of the bulk material. However, their active control, for example, by electronic stimuli, is challenging due to the absence of intrinsic piezoelectricity in the base material. Here, for large-scale nanoporous silicon cantilevers wetted by aqueous electrolytes, electrosorption-induced mechanical stress generation of up to 600 kPa that is reversible and adjustable at will by potential variations of ≈1 V is shown. Laser cantilever bending experiments in combination with in operando voltammetry and step coulombmetry allow this large electro-actuation to be traced to the concerted action of 100 billions of parallel nanopores per square centimeter cross-section and determination of the capacitive charge–stress coupling parameter upon ion adsorption and desorption as well as the intimately related stress actuation dynamics for perchloric and isotonic saline solutions. A comparison with planar silicon surfaces reveals mechanistic insights on the observed electrocapillarity (Hellmann–Feynman interactions) with respect to the importance of oxide formation and wall roughness on the single-nanopore scale. The observation of robust electrochemo-mechanical actuation in a mainstream semiconductor with wafer-scale, self-organized nanoporosity opens up novel opportunities for on-chip integrated stress generation and actuorics at exceptionally low operation voltages.
DOI: 10.15480/882.4102
ISSN: 1521-4095
Journal: Advanced materials 
Institute: Material- und Röntgenphysik M-2 
Document Type: Article
Project: Energy harvesting via wetting/drying cycles with nanoporous electrodes 
Projekt DEAL 
SFB 986: Teilprojekt B07 - Polymere in grenzflächenbestimmten Geometrien: Struktur, Dynamik und Funktion an planaren und in porösen Hybridsystemen 
Funded by: Deutsche Forschungsgemeinschaft (DFG) 
European Research Council (ERC)
Centre for Molecular Water Science CMWS
More Funding information: This work was supported by the Deutsche Forschungsgemeinschaft (DFG) within the Collaborative Research Initiative SFB 986 “Tailor-Made Multi-Scale Materials Systems” Project number 192346071. This project has also received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 964524 EHAWEDRY: “Energy harvesting via wetting-drying cycles with nanoporous electrodes” (H2020-FETOPEN-1-2021-2025). The authors also acknowledge the scientific exchange and support of the Centre for Molecular Water Science CMWS, Hamburg.
License: CC BY 4.0 (Attribution) CC BY 4.0 (Attribution)
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