Mechanoresponsive Polymerized Liquid Metal Networks

Thrasher, Carl J.; Farrell, Zachary; Morris, Nicholas J.; Willey, Carson L.; Tabor, Christopher E.

doi:10.1002/adma.201903864

Cited by 184 publications

(201 citation statements)

References 51 publications

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“…We attribute these decreases in resistance to the stress‐induced rupture a coalescence of LM inclusions. [ 42,43 ] In either case, compared to the large internal resistance of the SLM‐TENGs, these changes in resistance with strain will have negligible effect on the electrical output of SLM‐TENG. [ 44 ]…”

Section: Introductionmentioning

confidence: 99%

Ultrastretchable, Wearable Triboelectric Nanogenerator Based on Sedimented Liquid Metal Elastomer Composite

Pan

Liu

Ford

et al. 2020

Adv Materials Technologies

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Progress in soft and stretchable electronics depends on energy sources that are mechanically compliant, elastically deformable, and renewable. Energy harvesting using triboelectric nanogenerators (TENGs) made from soft materials provides a promising approach to address this critical need. Here, an elastomeric composite is introduced with sedimented liquid metal (LM) droplets for TENG‐based energy harvesting that relies on assembly of the LM to form phase‐separated conductive and insulating regions. The sedimented LM elastomer TENG (SLM‐TENG) exhibits ultrahigh stretchability (strain limit > 500% strain), skin‐like compliance (modulus < 60 kPa), reliable device stability (>10 000 cycles), and appreciable electrical output performance (max peak power density = 1 mW cm−2). SLM‐TENGs can be integrated with highly elastic stretchable fabrics, thereby enabling broad integration with wearable electronics. A stretchable and wearable SLM‐TENG is demonstrated that harvests energy from human motion through a patch attached to the knee or integrated into exercise clothing. This body‐mounted TENG device can generate enough electricity to fully power a wearable computing device (hygro‐thermometer with digital display) after 2.2 min of running on a treadmill.

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Section: Introductionmentioning

confidence: 99%

Ultrastretchable, Wearable Triboelectric Nanogenerator Based on Sedimented Liquid Metal Elastomer Composite

Pan

Liu

Ford

et al. 2020

Adv Materials Technologies

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“…Upon stretching, the LM network elongates and rotates to align along the stretch direction, which is evidenced in the micro‐CT images (Figure 1d, Figure S17, Supporting Information) and the projection analysis (Figure S18, Supporting Information). The rapid increase of the electrical conductivity along the stretch direction is ascribed to both stretch‐induced alignment and elongation of LMs 43. Our theoretical consideration reveals that for a representative LM wire with a tilt angle θ with respect to the stretch direction, stretch reduces its resistivity in the stretch direction by a factor α = λ −4 sin2θ + cos 2 θ, where λ = 1 + ε is the stretch This single factor also characterizes the stretch‐induced alignment of the LM wire such that α 1/2 = cosθ/cos θ′ , where θ′ is the tilt angle of the wire after stretch (Supporting Information, Section 9).…”

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confidence: 99%

“…The rapid increase of the electrical conductivity along the stretch direction is ascribed to both stretch-induced alignment and elongation of LMs. [43] Our theoretical consideration reveals that for a representative LM wire with a tilt angle θ with respect to the stretch direction, stretch reduces its resistivity in the stretch direction by a factor α = λ −4 sin2θ + cos 2 θ, where λ = 1 + ε is the stretch This single factor also characterizes the stretch-induced alignment of the LM wire such that α 1/2 = cosθ/cosθ′, where θ′ is the tilt angle of the wire after stretch (Supporting Information, Section 9). It is apparent that the larger the stretch λ, the higher level of the alignment, and the larger decrease in the resistivity.…”

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confidence: 99%

Highly Stretchable Polymer Composite with Strain‐Enhanced Electromagnetic Interference Shielding Effectiveness

et al. 2020

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Polymer composites with electrically conductive fillers have been developed as mechanically flexible, easily processable electromagnetic interference (EMI) shielding materials. Although there are a few elastomeric composites with nanostructured silvers and carbon nanotubes showing moderate stretchability, their EMI shielding effectiveness (SE) deteriorates consistently with stretching. Here, a highly stretchable polymer composite embedded with a three‐dimensional (3D) liquid‐metal (LM) network exhibiting substantial increases of EMI SE when stretched is reported, which matches the EMI SE of metallic plates over an exceptionally broad frequency range of 2.65–40 GHz. The electrical conductivities achieved in the 3D LM composite are among the state‐of‐the‐art in stretchable conductors under large mechanical deformations. With skin‐like elastic compliance and toughness, the material provides a route to meet the demands for emerging soft and human‐friendly electronics.

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“…[1][2][3] There has been a meaningful surge in reporting of deformable composites that incorporate LM ( Figure S1, Supporting Information), largely driven by interest in soft robotics and wearable devices. [4] Researchers have leveraged the high conductivity (3 × 10 4 S cm −1 ) and fluidity of LMs to synthesize composites [5] with high thermal conductivity, [6][7][8] high electrical conductivity, [9][10][11][12][13] enhanced/tunable mechanical properties, [14,15] electrical/mechanical self-healing capabilities, [16,17] and stimuli responsivity. [18][19][20][21][22] Like other natural and synthetic composites, proliferation of multifunctional materials for emerging technologies.…”

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confidence: 99%

Controlled Assembly of Liquid Metal Inclusions as a General Approach for Multifunctional Composites

et al. 2020

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functionality of LM composites relies on assembly and interactions between the matrix and filler. [11,23,24] To date, most of these LM composites have utilized silicone rubbers, where the functionality imparted by the matrix is limited to mechanical compliance and deformability, although a few meaningful exceptions exist (e.g., where the LM catalyzes/initiates poly mer ization). [19,21,25,26] Synthetic polymers can be designed with properties like stimuli responsivity, self-healing, processability, shape-morphing, and dynamic compliance and could be combined with LM to permit novel functionalities and processing capabilities. [27] The combination of finely tuned polymer synthesis with LM composite engineering will enable advanced applications like soft prosthetics, self-healing artificial skins, and 3D electronic materials. To achieve electrical conductivity, LM droplets within a composite must coalesce, for example, through an applied pressure (termed "mechanical sintering"). [28] Notably, the curing conditions and precursor composition dictate the network topology and resulting mechanical properties of the silicone matrix, which appear to influence whether an applied pressure forms percolation pathways for a LM composite. For example, LM composites using a commercially available silicone formulation (Sylgard 184, 10:1 weight ratio of Part A and Part B) can be electrically conductive after application of localized pressure [28] that coalesces LM droplets. However, permanent electrical conductivity has not been observed in LM composites that use a different commercially available silicone formulation (Ecoflex 00-30, 1:1 weight ratio of Part A and Part B), which is softer and more deformable than Sylgard 184. [8,20,29] This difference poses a limitation in generality of functionality for LM composites. Progress in LM composite engineering depends on a framework for materials synthesis that overcomes this limitation and enables integration of electrically conductive networks of LM in a wider range of media. Importantly, progress toward multifunctionality should include a focus on the properties of the matrix material. For LM composites, our group and others have demonstrated LM incorporation in functional matrix materials like hydrogels and shape-morphing polymers, but the predominate choice of matrix material has been silicone rubbers. [19,21,25,26] The development of an approach to achieve electrical conductivity by incorporating LM in functional polymer networks will facilitate Soft composites that use droplets of gallium-based liquid metal (LM) as the dispersion phase have the potential for transformative impact in multifunctional material engineering. However, it is unclear whether percolation pathways of LM can support high electrical conductivity in a wide range of matrix materials. This issue is addressed through an approach to LM composite synthesis that focuses on the interrelated effects of matrix curing/solidification and droplet formation. The combined influence of LM concentration, particle size, and ...

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Mechanoresponsive Polymerized Liquid Metal Networks

Cited by 184 publications

References 51 publications

Ultrastretchable, Wearable Triboelectric Nanogenerator Based on Sedimented Liquid Metal Elastomer Composite

Ultrastretchable, Wearable Triboelectric Nanogenerator Based on Sedimented Liquid Metal Elastomer Composite

Highly Stretchable Polymer Composite with Strain‐Enhanced Electromagnetic Interference Shielding Effectiveness

Controlled Assembly of Liquid Metal Inclusions as a General Approach for Multifunctional Composites

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