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Siddharth Doshi; Margaux OA Forner; Pingyu Wang; Salim El Hadwe; Amy T Jin; Gerwin Dijk; Kenneth Brinson; Juhwan Lim; Antonio Dominguez‐Alfaro; Carina Yi Jing Lim; Alberto Salleo; Damiano G Barone; Guosong Hong; Mark L Brongersma; Nicholas A Melosh; George G Malliaras; Scott T Keene
Thermal Processing Creates Water‐Stable PEDOT: PSS Films for Bioelectronics Journal Article
In: Advanced Materials, vol. 37, iss. 13, pp. 2415827, 2025.
@article{doshi2025thermal,
title = {Thermal Processing Creates Water‐Stable PEDOT: PSS Films for Bioelectronics},
author = {Siddharth Doshi and Margaux OA Forner and Pingyu Wang and Salim El Hadwe and Amy T Jin and Gerwin Dijk and Kenneth Brinson and Juhwan Lim and Antonio Dominguez‐Alfaro and Carina Yi Jing Lim and Alberto Salleo and Damiano G Barone and Guosong Hong and Mark L Brongersma and Nicholas A Melosh and George G Malliaras and Scott T Keene},
doi = {10.1002/adma.202415827},
year = {2025},
date = {2025-03-03},
urldate = {2025-03-03},
journal = {Advanced Materials},
volume = {37},
issue = {13},
pages = {2415827},
abstract = {Organic mixed ionic-electronic conductors have emerged as a key material for the development of bioelectronic devices due to their soft mechanical properties, biocompatibility, and high volumetric capacitance. In particular, PEDOT:PSS has become a choice material because it is highly conductive, easily processible, and commercially available. However, PEDOT:PSS is dispersible in water, leading to delamination of films when exposed to biological environments. For this reason, chemical cross\textendashlinking agents such as (3-glycidyloxypropyl)trimethoxysilane (GOPS) are used to stabilize PEDOT:PSS films in water, but at the cost of decreased electrical performance. Here, it is shown that PEDOT:PSS thin films become water-stable by simply baking at high temperatures (\>150 °C) for a short time (≈ 2 min). It is shown that heat-treated PEDOT:PSS films are as stable as their chemically-cross\textendashlinked counterparts, with their performance maintained for \>20 days both in vitro and in vivo. The heat-treated films eliminate electrically insulating cross\textendashlinkers, resulting in a 3× increase in volumetric capacitance. Applying thermal energy using a focused femtosecond laser enables direct patterning of 3D PEDOT:PSS microstructures. The thermal treatment method is compatible with a wide range of substrates and is readily substituted into existing workflows for manufacturing devices, enabling its rapid adoption in the field of bioelectronics.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Organic mixed ionic-electronic conductors have emerged as a key material for the development of bioelectronic devices due to their soft mechanical properties, biocompatibility, and high volumetric capacitance. In particular, PEDOT:PSS has become a choice material because it is highly conductive, easily processible, and commercially available. However, PEDOT:PSS is dispersible in water, leading to delamination of films when exposed to biological environments. For this reason, chemical cross–linking agents such as (3-glycidyloxypropyl)trimethoxysilane (GOPS) are used to stabilize PEDOT:PSS films in water, but at the cost of decreased electrical performance. Here, it is shown that PEDOT:PSS thin films become water-stable by simply baking at high temperatures (>150 °C) for a short time (≈ 2 min). It is shown that heat-treated PEDOT:PSS films are as stable as their chemically-cross–linked counterparts, with their performance maintained for >20 days both in vitro and in vivo. The heat-treated films eliminate electrically insulating cross–linkers, resulting in a 3× increase in volumetric capacitance. Applying thermal energy using a focused femtosecond laser enables direct patterning of 3D PEDOT:PSS microstructures. The thermal treatment method is compatible with a wide range of substrates and is readily substituted into existing workflows for manufacturing devices, enabling its rapid adoption in the field of bioelectronics.
Siddharth Doshi; Anqi Ji; Ali I Mahdi; Scott T Keene; Skyler P Selvin; Philippe Lalanne; Eric A Appel; Nicholas A Melosh; Mark L Brongersma
Electrochemically mutable soft metasurfaces Journal Article
In: Nature Materials, vol. 24, iss. 2, pp. 205-211, 2024.
@article{doshi2024electrochemically,
title = {Electrochemically mutable soft metasurfaces},
author = {Siddharth Doshi and Anqi Ji and Ali I Mahdi and Scott T Keene and Skyler P Selvin and Philippe Lalanne and Eric A Appel and Nicholas A Melosh and Mark L Brongersma},
doi = {10.1038/s41563-024-02042-4},
year = {2024},
date = {2024-11-13},
journal = {Nature Materials},
volume = {24},
issue = {2},
pages = {205-211},
abstract = {Active optical metasurfaces, capable of dynamically manipulating light in ultrathin form factors, enable novel interfaces between humans and technology. In such interfaces, soft materials bring many advantages based on their flexibility, compliance and large stimulus-driven responses. Here, we create electrochemically mutable, soft metasurfaces that capitalize on the swelling of soft conducting polymers to alter the shape and associated resonant response of metasurface elements. Such geometric tuning overcomes the typical trade-off between achieving substantial tuning and low optical loss that is intrinsic to dynamic metasurfaces relying on index tuning of materials. Using the commercial polymer PEDOT:PSS, we demonstrate dynamic, high-resolution colour tuning and high-diffraction-efficiency (\>19%) beam-steering devices that operate at CMOS-compatible voltages (~1.5 V). These results highlight how the deformability of soft materials can enable a class of high-performance metasurfaces that are suitable for body-worn technologies.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Active optical metasurfaces, capable of dynamically manipulating light in ultrathin form factors, enable novel interfaces between humans and technology. In such interfaces, soft materials bring many advantages based on their flexibility, compliance and large stimulus-driven responses. Here, we create electrochemically mutable, soft metasurfaces that capitalize on the swelling of soft conducting polymers to alter the shape and associated resonant response of metasurface elements. Such geometric tuning overcomes the typical trade-off between achieving substantial tuning and low optical loss that is intrinsic to dynamic metasurfaces relying on index tuning of materials. Using the commercial polymer PEDOT:PSS, we demonstrate dynamic, high-resolution colour tuning and high-diffraction-efficiency (>19%) beam-steering devices that operate at CMOS-compatible voltages (~1.5 V). These results highlight how the deformability of soft materials can enable a class of high-performance metasurfaces that are suitable for body-worn technologies.
Siddharth Doshi; Dominik Ludescher; Julian Karst; Moritz Floess; Johan Carlström; Bohan Li; Nofar Mintz Hemed; Yi-Shiou Duh; Nicholas A Melosh; Mario Hentschel; Mark Brongersma; Harald Giessen
Direct electron beam patterning of electro-optically active PEDOT: PSS Journal Article
In: Nanophotonics, no. 0, 2024.
@article{doshi2024direct,
title = {Direct electron beam patterning of electro-optically active PEDOT: PSS},
author = {Siddharth Doshi and Dominik Ludescher and Julian Karst and Moritz Floess and Johan Carlstr\"{o}m and Bohan Li and Nofar Mintz Hemed and Yi-Shiou Duh and Nicholas A Melosh and Mario Hentschel and Mark Brongersma and Harald Giessen},
doi = {10.1515/nanoph-2023-0640},
year = {2024},
date = {2024-01-04},
urldate = {2023-09-12},
journal = {Nanophotonics},
number = {0},
abstract = {The optical and electronic tunability of the conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) has enabled emerging applications as diverse as bioelectronics, flexible electronics, and micro- and nano-photonics. High-resolution spatial patterning of PEDOT:PSS opens up opportunities for novel active devices in a range of fields. However, typical lithographic processes require tedious indirect patterning and dry etch processes, while solution-processing methods such as ink-jet printing have limited spatial resolution. Here, we report a method for direct write nano-patterning of commercially available PEDOT:PSS through electron-beam induced solubility modulation. The written structures are water stable and maintain the conductivity as well as electrochemical and optical properties of PEDOT:PSS, highlighting the broad utility of our method. We demonstrate the potential of our strategy by preparing prototypical nano-wire structures with feature sizes down to 250 nm, an order of magnitude finer than previously reported direct write methods, opening the possibility of writing chip-scale microelectronic and optical devices. We finally use the high-resolution writing capabilities to fabricate electrically-switchable optical diffraction gratings. We show active switching in this archetypal system with \>95 % contrast at CMOS-compatible voltages of +2 V and −3 V, offering a route towards highly-miniaturized dynamic optoelectronic devices.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The optical and electronic tunability of the conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) has enabled emerging applications as diverse as bioelectronics, flexible electronics, and micro- and nano-photonics. High-resolution spatial patterning of PEDOT:PSS opens up opportunities for novel active devices in a range of fields. However, typical lithographic processes require tedious indirect patterning and dry etch processes, while solution-processing methods such as ink-jet printing have limited spatial resolution. Here, we report a method for direct write nano-patterning of commercially available PEDOT:PSS through electron-beam induced solubility modulation. The written structures are water stable and maintain the conductivity as well as electrochemical and optical properties of PEDOT:PSS, highlighting the broad utility of our method. We demonstrate the potential of our strategy by preparing prototypical nano-wire structures with feature sizes down to 250 nm, an order of magnitude finer than previously reported direct write methods, opening the possibility of writing chip-scale microelectronic and optical devices. We finally use the high-resolution writing capabilities to fabricate electrically-switchable optical diffraction gratings. We show active switching in this archetypal system with >95 % contrast at CMOS-compatible voltages of +2 V and −3 V, offering a route towards highly-miniaturized dynamic optoelectronic devices.
