ToF-SIMS characterization of silk fibroin and polypyrrole composite actuators

Bradshaw, Nathan P.; Severt, Sean Y.; Wang, Zhaoying; Fengel, Carly V.; Larson, Jesse D.; Zhu, Zihua; Murphy, Ana A.; Leger, Janelle

doi:10.1016/j.synthmet.2015.08.031

Cited by 11 publications

(10 citation statements)

References 26 publications

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“…Conducting polymers can be used in actuation, but as these materials are often brittle, fillers are often used to improve the mechanical properties. As an example, Bradshaw et al designed actuators based on interpenetrating networks of polypyrrole (PPy) and silk fibroin, 130 a system of potential viability for in vivo applications. They used ToF‐SIMS depth profiling to examine changes in both dopant and ion concentration after actuation in phosphate buffered saline (which contains both phosphate and chloride ions).…”

Section: Polymer Compositesmentioning

confidence: 99%

Characterization of polymeric surfaces and interfaces using time‐of‐flight secondary ion mass spectrometry

Mei

Laws

Terlier

et al. 2021

Journal of Polymer Science

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Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is used for chemical analysis of surfaces. ToF-SIMS is a powerful tool for polymer science because it detects a broad mass range with good mass resolution, thereby distinguishing between polymers that have similar elemental compositions and/or the same types of functional groups. Chemical labeling techniques that enhance contrast, such as deuterating or staining one constituent, are generally unnecessary. ToF-SIMS can generate both two-dimensional images and three-dimensional depth profiles, where each pixel in an image is associated with a complete mass spectrum. This Review begins by introducing the principles of ToF-SIMS measurements, including instrumentation, modes of operation, strategies for data analysis, and strengths/limitations when characterizing polymer surfaces. The sections that follow describe applications in polymer science that benefit from characterization by ToF-SIMS, including thin films and coatings, polymer blends, composites, and electronic materials. The examples selected for discussion showcase the three standard modes of operation (spectral analysis, imaging, and depth profiling) and highlight practical considerations that relate to experimental design and data processing. We conclude with brief comments about broader opportunities for ToF-SIMS in polymer science.

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Section: Polymer Compositesmentioning

confidence: 99%

Characterization of polymeric surfaces and interfaces using time‐of‐flight secondary ion mass spectrometry

Mei

Laws

Terlier

et al. 2021

Journal of Polymer Science

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“…In all reactions, para-toluenesulfonic acid (pTSA) was added to serve as a small molecule dopant, as previous studies found pTSA to be an effective and stable dopant for our silk-PPy composites [19]. Polymerizations initiated with FeCl 3 in the presence of pTSA result in doping with both chloride and tosylate [29], therefore polymerizations employing Fe(OTs) 3 were also investigated to produce polymers with tosylate anions as the sole dopant [30]. These larger organic acids are trapped in the PPy matrix more effectively than chloride ions, and typically give rise to more stable, conductive materials [31,32].…”

Section: Synthesis and Characterization Of Silk-ppy Compositesmentioning

confidence: 99%

“…While not significantly different than the 1:1 pyrrole:FeCl 3 films, the Fe(OTs) 3 films were slightly more stable over time, likely due to diminished dopant leaching [31,32] as these films have tosylate anions as the sole dopant. Films synthesized with FeCl 3 retain some chloride ions [29], which are more mobile than tosylate and can readily leach and de-dope the polymer matrix over time. Given this information, more extensive washing prior to use to extract the bulk of the unbound ions, followed by dry long-term storage would be recommended for devices intended for implantation.…”

Section: Synthesis and Characterization Of Silk-ppy Compositesmentioning

confidence: 99%

Enhanced actuation performance of silk-polypyrrole composites

Larson

Fengel

Bradshaw

et al. 2017

Materials Chemistry and Physics

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Recently we have shown that a composite material of silk and the conducting polymer polypyrrole (PPy) has promising characteristics for use as a bending bilayer actuator. In this study, the reaction conditions were varied for the in situ incorporation of polypyrrole into silk films during pyrrole polymerization. While surface morphology and mechanical properties were minimally affected, polymerization conditions were identified where the resistivity, stability of the films during storage and stability during prolonged electrochemical cycling were dramatically improved. When fabricated into bilayer-type electromechanical actuation devices, stress and strain generation, as well as the stability during repeated actuation, was found to be superior for silk-polypyrrole composite films with improved electrical properties.

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“…Previously, our group developed strategies for incorporating conductive PPy into silk structures to form a completely integrated interpenetrating network (IPN) of silk and PPy, and demonstrated their use as electromechanical bilayer bending actuators . These silk‐PPy bilayer actuators were capable of generating stresses comparable to human muscle (>0.1 MPa) and were electrochemically stable .…”

Section: Introductionmentioning

confidence: 99%

Performance of silk‐polypyrrole bilayer actuators under biologically relevant conditions

Hagler

Peterson

Murphy

et al. 2018

J of Applied Polymer Sci

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Biocompatible actuators that are capable of controlled movement and can function under biologically relevant conditions are of significant interest for biomedical applications. Previously, we have demonstrated that a composite material of silk biopolymer and the conducting polymer poly(pyrrole) (PPy) can be formed into a functional bilayer bending actuator. Further, these silk-PPy composites can generate forces comparable to human muscle (>0.1 MPa) making them ideal candidates for interfacing with biological tissues. Here, we explore the performance of these silk-PPy composite bilayer actuators under biologically relevant conditions including exposure to proteins, serum, enzymes, and biologically relevant temperatures. Free-end bending actuation performance, current response, force generation, and mass degradation under these conditions were investigated. We find that under the conditions tested here, the performance of our silk-PPy composites is sensitive to both protein serum and enzyme type, as well as to the temperature at which the devices are actuated. However, the silk-PPy actuators retained their functionality under all conditions tested, demonstrating the ability to bend, generate forces, and conduct currents at comparable levels to devices tested under standard operating conditions. The results suggest that our silk-PPy actuators are promising candidates for implantation in vivo and for interfacing with biological systems.

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ToF-SIMS characterization of silk fibroin and polypyrrole composite actuators

Cited by 11 publications

References 26 publications

Characterization of polymeric surfaces and interfaces using time‐of‐flight secondary ion mass spectrometry

Characterization of polymeric surfaces and interfaces using time‐of‐flight secondary ion mass spectrometry

Enhanced actuation performance of silk-polypyrrole composites

Performance of silk‐polypyrrole bilayer actuators under biologically relevant conditions

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