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Printable elastic conductors with a high conductivity for electronic textile applications.

Matsuhisa N, Kaltenbrunner M, Yokota T, Jinno H, Kuribara K, Sekitani T, Someya T - Nat Commun (2015)

Bottom Line: The development of advanced flexible large-area electronics such as flexible displays and sensors will thrive on engineered functional ink formulations for printed electronics where the spontaneous arrangement of molecules aids the printing processes.The elastic conductor ink is comprised of Ag flakes, a fluorine rubber and a fluorine surfactant.The fluorine surfactant constitutes a key component which directs the formation of surface-localized conductive networks in the printed elastic conductor, leading to a high conductivity and stretchability.

View Article: PubMed Central - PubMed

Affiliation: 1] Electrical and Electronic Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan [2] Advanced Leading Graduate Course for Photon Science (ALPS), 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.

ABSTRACT
The development of advanced flexible large-area electronics such as flexible displays and sensors will thrive on engineered functional ink formulations for printed electronics where the spontaneous arrangement of molecules aids the printing processes. Here we report a printable elastic conductor with a high initial conductivity of 738 S cm(-1) and a record high conductivity of 182 S cm(-1) when stretched to 215% strain. The elastic conductor ink is comprised of Ag flakes, a fluorine rubber and a fluorine surfactant. The fluorine surfactant constitutes a key component which directs the formation of surface-localized conductive networks in the printed elastic conductor, leading to a high conductivity and stretchability. We demonstrate the feasibility of our inks by fabricating a stretchable organic transistor active matrix on a rubbery stretchability-gradient substrate with unimpaired functionality when stretched to 110%, and a wearable electromyogram sensor printed onto a textile garment.

No MeSH data available.


Related in: MedlinePlus

Highly stretchable elastic conductors.(a) Fabrication process of elastic conductor ink. Upper picture, elastic conductor ink. Scale bar, 10 mm. Lower picture, printed elastic conductor with high resolution. Scale bar, 100 μm. (b) Printed elastic conductor and demonstration of the stretchability. Scale bar, 10 mm. (c) Conductivity dependence on tensile strain of printed elastic conductor with and without surfactant. The maximum stretchability of elastic conductor with surfactant is limited by the strain limit of the substrate. (d) A comparison of this work to recent work in elastic conductors. Data points are extracted from the following papers: light blue filled triangle, Ag nanowires (Ag NW)—the study by Xu and Zhu23 (calculated from resistance change under the assumption that the total volume does not change); orange open square, Au nanoparticles (Au NP)—the study by Kim et al.22; blue open triangle, Ag nanoparticles (Ag NP)—the study by Park et al.21; purple open circle, multi walled carbon nanotubes (MWCNT)—the study by Chun et al.24; black filled square, single walled carbon nanotubes (SWCNT)—the study by Sekitani et al.15; light purple filled diamond, polyaniline (PANI)—the study by Stoyanov et al.25; red filled circle, this study (corresponds to c). (e) Initial conductivity and stretchability dependence on surfactant content. The weight ratio of Ag flakes, fluorine rubber and 4-methyl-2-pentanone was fixed at 3:1:2 (volume fraction, 1:1.94:8.74). Red circles, initial conductivity; blue squares, stretchability. (f) Initial conductivity and stretchability dependence on the Ag flakes content. The weight ratio of fluorine rubber, 4-methyl-2-pentanone and surfactant solution was fixed to 1:2:1 (volume fraction, 1:4.5:1.64). Error bars in e,f represent standard error.
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f1: Highly stretchable elastic conductors.(a) Fabrication process of elastic conductor ink. Upper picture, elastic conductor ink. Scale bar, 10 mm. Lower picture, printed elastic conductor with high resolution. Scale bar, 100 μm. (b) Printed elastic conductor and demonstration of the stretchability. Scale bar, 10 mm. (c) Conductivity dependence on tensile strain of printed elastic conductor with and without surfactant. The maximum stretchability of elastic conductor with surfactant is limited by the strain limit of the substrate. (d) A comparison of this work to recent work in elastic conductors. Data points are extracted from the following papers: light blue filled triangle, Ag nanowires (Ag NW)—the study by Xu and Zhu23 (calculated from resistance change under the assumption that the total volume does not change); orange open square, Au nanoparticles (Au NP)—the study by Kim et al.22; blue open triangle, Ag nanoparticles (Ag NP)—the study by Park et al.21; purple open circle, multi walled carbon nanotubes (MWCNT)—the study by Chun et al.24; black filled square, single walled carbon nanotubes (SWCNT)—the study by Sekitani et al.15; light purple filled diamond, polyaniline (PANI)—the study by Stoyanov et al.25; red filled circle, this study (corresponds to c). (e) Initial conductivity and stretchability dependence on surfactant content. The weight ratio of Ag flakes, fluorine rubber and 4-methyl-2-pentanone was fixed at 3:1:2 (volume fraction, 1:1.94:8.74). Red circles, initial conductivity; blue squares, stretchability. (f) Initial conductivity and stretchability dependence on the Ag flakes content. The weight ratio of fluorine rubber, 4-methyl-2-pentanone and surfactant solution was fixed to 1:2:1 (volume fraction, 1:4.5:1.64). Error bars in e,f represent standard error.

Mentions: The elastic conductor ink is prepared by adding Ag flakes (∼3.4 μm) as conductive fillers to an elastomeric fluorine copolymer (DAI-EL G801) with 4-methyl-2-pentanone as an organic solvent, together with a water-based fluorine surfactant (Zonyl FS-300, hereafter referred to as surfactant) (Fig. 1a). The size distribution of the Ag flakes, as obtained from Sigma Aldrich, is shown in Supplementary Fig. 1. The addition of surfactant improves the affinity of Ag flakes to the fluoropolymer matrix by modifying the Ag surface and by plasticizing the fluorine copolymer. This is discussed in more detail later in the manuscript. The conductive ink can be readily patterned with conventional printing techniques such as stencil printing or dispensers at high resolutions (50-μm line width, Fig. 1a) and into arbitrarily shaped, highly stretchable wirings like the 260% stretchable logo in Fig. 1b. The mixing ratio of the four ink components is a key parameter to control the electrical and mechanical properties of the resulting elastic conductors. Careful optimization of the mass ratio between Ag flakes:fluorine rubber:4-methyl-2-pentanone:surfactant to 3:1:2:1 results in the simultaneously highest conductivity and stretchability. The elastic conductor inks are patterned on 150-μm thick polydimethylsiloxane (PDMS) substrates by stencil printing to evaluate their electrical and mechanical characteristics (see also Methods and Supplementary Figs 2 and 3). PDMS is chosen as a supporting substrate due to its ease of processing and tunable Young's modulus. Comparing the conductivities of elastic conductors with and without surfactant while undergoing uniaxial tensile strain (Fig. 1c) shows that the initial conductivity (at zero strain) of the printed conductor containing surfactant is as large as the reference without surfactant and reaches 738 S cm−1. Most strikingly, introducing surfactant to the ink dramatically improves the stretchability (maximum strain before failure) of the elastic conductor, from a modest 27% for the reference to over 200% for the surfactant containing formulation. Stretchable forms of LED lightning and other high power electronics will greatly benefit from such high conductivity and stretchability, a combination of properties notoriously difficult to achieve. The conductivities at the maximum sustainable strain for state-of-the-art solution-processed stretchable conductors152122232425 are compared in Fig. 1d. The conductivities as a function of strain are also compared in Supplementary Fig. 4. Our printed conductors reach a conductivity of 182 S cm−1 at a strain of 215%, currently the highest value reported for stretchable conductors that can be stretched >150%. Remarkably, device failure above strains of 200% always occurs due to rupturing of the PDMS substrate, not due to loss of conductivity or mechanical failure of the printed conductor itself. This suggests that further improvements are feasible by using more mechanically robust substrates which have an appropriate modulus and good adhesion with the printed elastomer. Porous stretchable substrates like polyuretahne foam or stretchable substrates that can be slightly dissolved with 4-methyl-2-pentanone are promising candidates.


Printable elastic conductors with a high conductivity for electronic textile applications.

Matsuhisa N, Kaltenbrunner M, Yokota T, Jinno H, Kuribara K, Sekitani T, Someya T - Nat Commun (2015)

Highly stretchable elastic conductors.(a) Fabrication process of elastic conductor ink. Upper picture, elastic conductor ink. Scale bar, 10 mm. Lower picture, printed elastic conductor with high resolution. Scale bar, 100 μm. (b) Printed elastic conductor and demonstration of the stretchability. Scale bar, 10 mm. (c) Conductivity dependence on tensile strain of printed elastic conductor with and without surfactant. The maximum stretchability of elastic conductor with surfactant is limited by the strain limit of the substrate. (d) A comparison of this work to recent work in elastic conductors. Data points are extracted from the following papers: light blue filled triangle, Ag nanowires (Ag NW)—the study by Xu and Zhu23 (calculated from resistance change under the assumption that the total volume does not change); orange open square, Au nanoparticles (Au NP)—the study by Kim et al.22; blue open triangle, Ag nanoparticles (Ag NP)—the study by Park et al.21; purple open circle, multi walled carbon nanotubes (MWCNT)—the study by Chun et al.24; black filled square, single walled carbon nanotubes (SWCNT)—the study by Sekitani et al.15; light purple filled diamond, polyaniline (PANI)—the study by Stoyanov et al.25; red filled circle, this study (corresponds to c). (e) Initial conductivity and stretchability dependence on surfactant content. The weight ratio of Ag flakes, fluorine rubber and 4-methyl-2-pentanone was fixed at 3:1:2 (volume fraction, 1:1.94:8.74). Red circles, initial conductivity; blue squares, stretchability. (f) Initial conductivity and stretchability dependence on the Ag flakes content. The weight ratio of fluorine rubber, 4-methyl-2-pentanone and surfactant solution was fixed to 1:2:1 (volume fraction, 1:4.5:1.64). Error bars in e,f represent standard error.
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f1: Highly stretchable elastic conductors.(a) Fabrication process of elastic conductor ink. Upper picture, elastic conductor ink. Scale bar, 10 mm. Lower picture, printed elastic conductor with high resolution. Scale bar, 100 μm. (b) Printed elastic conductor and demonstration of the stretchability. Scale bar, 10 mm. (c) Conductivity dependence on tensile strain of printed elastic conductor with and without surfactant. The maximum stretchability of elastic conductor with surfactant is limited by the strain limit of the substrate. (d) A comparison of this work to recent work in elastic conductors. Data points are extracted from the following papers: light blue filled triangle, Ag nanowires (Ag NW)—the study by Xu and Zhu23 (calculated from resistance change under the assumption that the total volume does not change); orange open square, Au nanoparticles (Au NP)—the study by Kim et al.22; blue open triangle, Ag nanoparticles (Ag NP)—the study by Park et al.21; purple open circle, multi walled carbon nanotubes (MWCNT)—the study by Chun et al.24; black filled square, single walled carbon nanotubes (SWCNT)—the study by Sekitani et al.15; light purple filled diamond, polyaniline (PANI)—the study by Stoyanov et al.25; red filled circle, this study (corresponds to c). (e) Initial conductivity and stretchability dependence on surfactant content. The weight ratio of Ag flakes, fluorine rubber and 4-methyl-2-pentanone was fixed at 3:1:2 (volume fraction, 1:1.94:8.74). Red circles, initial conductivity; blue squares, stretchability. (f) Initial conductivity and stretchability dependence on the Ag flakes content. The weight ratio of fluorine rubber, 4-methyl-2-pentanone and surfactant solution was fixed to 1:2:1 (volume fraction, 1:4.5:1.64). Error bars in e,f represent standard error.
Mentions: The elastic conductor ink is prepared by adding Ag flakes (∼3.4 μm) as conductive fillers to an elastomeric fluorine copolymer (DAI-EL G801) with 4-methyl-2-pentanone as an organic solvent, together with a water-based fluorine surfactant (Zonyl FS-300, hereafter referred to as surfactant) (Fig. 1a). The size distribution of the Ag flakes, as obtained from Sigma Aldrich, is shown in Supplementary Fig. 1. The addition of surfactant improves the affinity of Ag flakes to the fluoropolymer matrix by modifying the Ag surface and by plasticizing the fluorine copolymer. This is discussed in more detail later in the manuscript. The conductive ink can be readily patterned with conventional printing techniques such as stencil printing or dispensers at high resolutions (50-μm line width, Fig. 1a) and into arbitrarily shaped, highly stretchable wirings like the 260% stretchable logo in Fig. 1b. The mixing ratio of the four ink components is a key parameter to control the electrical and mechanical properties of the resulting elastic conductors. Careful optimization of the mass ratio between Ag flakes:fluorine rubber:4-methyl-2-pentanone:surfactant to 3:1:2:1 results in the simultaneously highest conductivity and stretchability. The elastic conductor inks are patterned on 150-μm thick polydimethylsiloxane (PDMS) substrates by stencil printing to evaluate their electrical and mechanical characteristics (see also Methods and Supplementary Figs 2 and 3). PDMS is chosen as a supporting substrate due to its ease of processing and tunable Young's modulus. Comparing the conductivities of elastic conductors with and without surfactant while undergoing uniaxial tensile strain (Fig. 1c) shows that the initial conductivity (at zero strain) of the printed conductor containing surfactant is as large as the reference without surfactant and reaches 738 S cm−1. Most strikingly, introducing surfactant to the ink dramatically improves the stretchability (maximum strain before failure) of the elastic conductor, from a modest 27% for the reference to over 200% for the surfactant containing formulation. Stretchable forms of LED lightning and other high power electronics will greatly benefit from such high conductivity and stretchability, a combination of properties notoriously difficult to achieve. The conductivities at the maximum sustainable strain for state-of-the-art solution-processed stretchable conductors152122232425 are compared in Fig. 1d. The conductivities as a function of strain are also compared in Supplementary Fig. 4. Our printed conductors reach a conductivity of 182 S cm−1 at a strain of 215%, currently the highest value reported for stretchable conductors that can be stretched >150%. Remarkably, device failure above strains of 200% always occurs due to rupturing of the PDMS substrate, not due to loss of conductivity or mechanical failure of the printed conductor itself. This suggests that further improvements are feasible by using more mechanically robust substrates which have an appropriate modulus and good adhesion with the printed elastomer. Porous stretchable substrates like polyuretahne foam or stretchable substrates that can be slightly dissolved with 4-methyl-2-pentanone are promising candidates.

Bottom Line: The development of advanced flexible large-area electronics such as flexible displays and sensors will thrive on engineered functional ink formulations for printed electronics where the spontaneous arrangement of molecules aids the printing processes.The elastic conductor ink is comprised of Ag flakes, a fluorine rubber and a fluorine surfactant.The fluorine surfactant constitutes a key component which directs the formation of surface-localized conductive networks in the printed elastic conductor, leading to a high conductivity and stretchability.

View Article: PubMed Central - PubMed

Affiliation: 1] Electrical and Electronic Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan [2] Advanced Leading Graduate Course for Photon Science (ALPS), 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.

ABSTRACT
The development of advanced flexible large-area electronics such as flexible displays and sensors will thrive on engineered functional ink formulations for printed electronics where the spontaneous arrangement of molecules aids the printing processes. Here we report a printable elastic conductor with a high initial conductivity of 738 S cm(-1) and a record high conductivity of 182 S cm(-1) when stretched to 215% strain. The elastic conductor ink is comprised of Ag flakes, a fluorine rubber and a fluorine surfactant. The fluorine surfactant constitutes a key component which directs the formation of surface-localized conductive networks in the printed elastic conductor, leading to a high conductivity and stretchability. We demonstrate the feasibility of our inks by fabricating a stretchable organic transistor active matrix on a rubbery stretchability-gradient substrate with unimpaired functionality when stretched to 110%, and a wearable electromyogram sensor printed onto a textile garment.

No MeSH data available.


Related in: MedlinePlus