Research ArticleSOFT ROBOTS

Electronic skins for soft, compact, reversible assembly of wirelessly activated fully soft robots

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Science Robotics  30 May 2018:
Vol. 3, Issue 18, eaas9020
DOI: 10.1126/scirobotics.aas9020
  • Fig. 1 Skin-like soft driving system for wirelessly activated fully soft robots.

    (A) Conceptual illustration of e-skin–mediated soft robotic assembly and wireless activation. The e-skin pair can be softly, compactly, and reversibly assembled into separate soft body frames (robot and human); wirelessly interact with each other; and then activate and control the robot, realizing fully soft robots. (B) Activating and operating behavior of the integrated soft robot visualized by thermographic mapping. In this design, dynamic actuation profiles can be shared with every robot part. (C) The embedded controlling e-skin that interacts with human for user-interactive pressure sensing.

  • Fig. 2 Fragmented SHE design of e-skins for fine conformability.

    (A) Exploded view schematic illustration of e-skins. Inset images: Optical image (left) and corresponding surface strain field (right), evaluated by finite element analysis, of the unit SMD region. (B) Layout and functional description of the e-skin pair: controlling e-skin (left) and activating e-skin (right). Electronic functionalities for soft driving system, such as sensors, electronic control circuit and communication board, and actuating drivers, are spatially fragmented into two parts, providing wireless driving capability. (C) Photograph of the e-skin that wraps around the cylindrical rod (radius = 1 mm). The fragmented circuit configuration with the standard SMD dimensions (≤1.5 mm by 1.5 mm by 0.6 mm), and engineered pitch (≥2.3 mm) achieved the target deformation curvature (1/1.5 mm−1) in both outward and inward bending states (inset images) (see fig. S10 and note S1 for details on design criteria). (D) Extreme compliance of the e-skin that conforms to the corrugated surface (Al foil) with multiple curvatures.

  • Fig. 3 Wireless four-state inter-skin communication.

    (A) Schematic diagram and representative signal profiles of the devised circuit architecture. (B) Encoding/decoding mechanism of the customized serializing encoder/deserializing decoder. (C to G) Typical encoded waveforms in each input state (default, A to D) measured at the encoder output (before transmitting, blue line) and decoder input (after receiving, red line). (H) Magnified view in the waveform in (G). Wireless synchronization between the e-skins within the margin of communication delay of ~12.6 μs was confirmed without meaningful degradation under 25% biaxial strain. (I) Real-time decoding process of the dynamic, randomly encoded signal sequences. The decoding capability shows real-time synchronized sampling with the minimum decoding resolution of ~8 ms. (J) Schematic illustration of an experimental setup for testing the reliability of the wireless inter-skin communication under artificial noise condition. (K) Fourier analysis data on randomized, encoded (blue) and nonencoded (green) signals (typical waveforms are described in fig. S16C). R(jω) is defined as the Fourier-transformed pseudo-random bit sequence signals. (L) Wireless data transmission yield (Ydata) of encoded and nonencoded signals as a function of deskin defined in (J).

  • Fig. 4 E-skin–mediated assembly and wireless activation of a soft robotic hand.

    (A) Schematic and corresponding photographic images of soft, compact assembly steps for the integrated design of a fully soft robotic hand. A body architecture of the robot was fabricated by printing PEDOT:PSS thin films at finger positions. By using the prepared activating e-skin, the integration and activation process was carried out through a simple lamination process. (B) Sequential actuation profiles of an individual bilayer (PEDOT:PSS/PDMS) soft actuator with increasing applied voltages (0 to 15 V). (C) Radius of curvature and power consumption of an individual soft actuator as a function of the applied voltage (0 to 15 V). (D) Representative photographic and thermographic images of the operating e-skin pair and corresponding four-state manipulation of the soft robotic hand: the operating controlling e-skin (top) and activated soft robotic hand (bottom). On the basis of the specific digital mixing (fig. S14), each input state is programmed to activate different robotic fingers (A, “1, 2, 3, 4, 5”; B, “1, 2”; C, “3”; D, “4, 5”). According to the operational state of robotic fingers, in-skin current distribution was discriminated.

  • Fig. 5 Coadaptive movements of fully soft robotic design.

    (A to D) Thermographic images of the activated fully soft robot subject to multidimensional deformations such as outward (A) and inward bending (B), stretching (~20% diagonal strain) (C), and folding (D). Because of soft, thin, and lightweight features, the e-skin can equally share the sequential deformation profiles of the robot body. (E) Experimental design showing that the fully soft robot met the constrained environment, whose cross section (33 mm) was smaller than the robot size (62 mm). (F and G) Sequential coadaptive movements allow the robot to pass through a tiny cross section at a folded state (F) and then operate with full motion states at an unfolded state (G). (H) Sequential thermographic image frames that verify successful coadaptive movements and reliable operation of the robot throughout the entire flow of deformation steps.

  • Fig. 6 Universal soft robotic activation based on reversible assembly.

    (A) Process flow of consecutive soft robotic activation by sequential lamination processes. Specifically, three different soft robotic hands with distinct finger designs (normal design for robot 1 and spread finger design for robots 2 and 3) and deformation states [placed onto the flat (robots 1 and 2) and curvilinear surface (robot 3) like a mannequin’s hand] were addressed. (B) Enlarged view of each soft robotic hand before the activating e-skin was mounted. (C) Photograph of the laminated controlling e-skin showing good skin conformability. (D) Enlarged view of wireless manipulation of soft robotic hands with distinct operation states. For comparison, different actuation states in response to the input types (C, D, and B states) were demonstrated for each robot. (E) Sequential photographs of the controlling e-skin in each input state (C, D, and B).

Supplementary Materials

  • robotics.sciencemag.org/cgi/content/full/3/18/eaas9020/DC1

    Note S1. Fully printable SHE assembly and its physical properties.

    Note S2. Design criteria of fragmented SHE design for fine conformability to soft robots.

    Note S3. Details on wireless inter-skin communication flow.

    Note S4. Details on experimental setup for the reliability test under artificial noise condition.

    Fig. S1. Schematic circuit diagrams of the devised e-skin pair.

    Fig. S2. SMD-level fragmentation of electronic functionalities.

    Fig. S3. Circuit designs based on the homemade circuit routing program.

    Fig. S4. Fully printable SMD assembly for e-skins.

    Fig. S5. Multilayer interconnection design in e-skins.

    Fig. S6. Two-dimensional wrinkled morphologies of an e-skin surface.

    Fig. S7. Comparison between printed strain-isolating structures.

    Fig. S8. Experimental verification of the gradual strain-absorbing effect near the SMD contact areas.

    Fig. S9. Three-dimensional finite element analysis on printed coplanar strain-isolating architectures.

    Fig. S10. Design criteria of fragmented SHE design for fine conformability.

    Fig. S11. Stretchability and conformability to dynamic surfaces.

    Fig. S12. Signal quantizing module in the controlling e-skin.

    Fig. S13. Continuous monitoring of wireless inter-skin communication.

    Fig. S14. Digital mixing of decoded signals in the activating e-skin.

    Fig. S15. An experimental setup for the reliability test.

    Fig. S16. Details on experimental setup for the reliability test of encoded and nonencoded signals under artificial noise condition.

    Fig. S17. Bending force of the PEDOT:PSS soft actuator.

    Fig. S18. Coadaptive movement of the e-skin–integrated soft robot laminated onto a crumpled convex surface.

    Table S1. Specifications of the used SMDs.

    Movie S1. Thermographic visualization of real-time activation of a soft robotic hand.

    Movie S2. Wireless operation of the e-skin–integrated soft robotic hand via wireless inter-skin communication.

    Movie S3. Coadaptive movement of a fully soft robotic hand in a confined space.

    Movie S4. E-skin–mediated universal soft robotic activation.

  • Supplementary Materials

    Supplementary Material for:

    Electronic skins for soft, compact, reversible assembly of wirelessly activated fully soft robots

    Junghwan Byun, Yoontaek Lee, Jaeyoung Yoon, Byeongmoon Lee, Eunho Oh, Seungjun Chung, Takhee Lee, Kyu-Jin Cho,* Jaeha Kim,* Yongtaek Hong*

    *Corresponding author. Email: yongtaek{at}snu.ac.kr (Y.H.); jaeha{at}snu.ac.kr (J.K.); kjcho{at}snu.ac.kr (K.-J.C.)

    Published 30 May 2018, Sci. Robot. 3, eaas9020 (2018)
    DOI: 10.1126/scirobotics.aas9020

    This PDF file includes:

    • Note S1. Fully printable SHE assembly and its physical properties
    • Note S2. Design criteria of fragmented SHE design for fine conformability to soft robots
    • Note S3. Details on wireless inter-skin communication flow
    • Note S4. Details on experimental setup for the reliability test under artificial noise condition
    • Fig. S1. Schematic circuit diagrams of the devised e-skin pair.
    • Fig. S2. SMD-level fragmentation of electronic functionalities.
    • Fig. S3. Circuit designs based on the homemade circuit routing program.
    • Fig. S4. Fully printable SMD assembly for e-skins.
    • Fig. S5. Multilayer interconnection design in e-skins.
    • Fig. S6. Two-dimensional wrinkled morphologies of an e-skin surface.
    • Fig. S7. Comparison between printed strain-isolating structures.
    • Fig. S8. Experimental verification of the gradual strain-absorbing effect near the SMD contact areas.
    • Fig. S9. Three-dimensional finite element analysis on printed coplanar strain-isolating architectures.
    • Fig. S10. Design criteria of fragmented SHE design for fine conformability.
    • Fig. S11. Stretchability and conformability to dynamic surfaces.
    • Fig. S12. Signal quantizing module in the controlling e-skin.
    • Fig. S13. Continuous monitoring of wireless inter-skin communication.
    • Fig. S14. Digital mixing of decoded signals in the activating e-skin.
    • Fig. S15. An experimental setup for the reliability test.
    • Fig. S16. Details on experimental setup for the reliability test of encoded and nonencoded signals under artificial noise condition.
    • Fig. S17. Bending force of the PEDOT:PSS soft actuator.
    • Fig. S18. Coadaptive movement of the e-skin–integrated soft robot laminated onto a crumpled convex surface.
    • Table S1. Specifications of the used SMDs.

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    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Thermographic visualization of real-time activation of a soft robotic hand.
    • Movie S2 (.mp4 format). Wireless operation of the e-skin–integrated soft robotic hand via wireless inter-skin communication.
    • Movie S3 (.mp4 format). Coadaptive movement of a fully soft robotic hand in a confined space.
    • Movie S4 (.mp4 format). E-skin–mediated universal soft robotic activation.

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