Shape changing thin films powered by DNA hybridization

Journal name:
Nature Nanotechnology
Year published:
Published online

Active materials that respond to physical1, 2, 3 and chemical4, 5, 6 stimuli can be used to build dynamic micromachines that lie at the interface between biological systems and engineered devices7, 8. In principle, the specific hybridization of DNA can be used to form a library of independent, chemically driven actuators for use in such microrobotic applications and could lead to device capabilities that are not possible with polymer- or metal-layer-based approaches. Here, we report shape changing films9 that are powered by DNA strand exchange reactions with two different domains that can respond to distinct chemical signals. The films are formed from DNA-grafted gold nanoparticles10, 11 using a layer-by-layer deposition process. Films consisting of an active and a passive layer show rapid, reversible curling in response to stimulus DNA strands added to solution. Films consisting of two independently addressable active layers display a complex suite of repeatable transformations, involving eight mechanochemical states and incorporating self-righting behaviour.

At a glance


  1. Shape changing DNA–GNP films are fabricated via layer-by-layer deposition using a PDMS gasket.
    Figure 1: Shape changing DNA–GNP films are fabricated via layer-by-layer deposition using a PDMS gasket.

    a, Illustration of a thin film changing shape by DNA strand exchange reaction. b, Schematics of four different GNPs conjugated with A (green), B (blue), C (red) and D (magenta) oligonucleotides, respectively. Oligonucleotides are modified with a thiol group at the 5′-end for A and D, and the 3′-end for B and C for conjugation on GNPs. c, Layer-by-layer deposition for fabrication of multi-domain DNA–GNP films. For DNA–GNP solutions, 20 nM of DNA–GNPs and 200 nM of the corresponding linker and filler oligonucleotides were dispersed in 0.3 M PBS. To maintain the hybridization equilibrium, 80 nM of linker and filler oligonucleotides were added to 0.3 M PBS rinsing buffer. d, Representative DNA–GNP film that has two different domains with (AB)M(AC)N laid down using the layer-by-layer deposition technique described in b. Each domain is composed of two different DNA–GNPs that have oligonucleotides ending with 3′ (green) and 5′ (blue), respectively, forming ‘end-to-end’ binding with linker oligonucleotides. e, Schematics of the micropatterning of DNA–GNP films using a thin PDMS gasket.

  2. Strand exchange reactions enable reversible DNA–GNP swelling.
    Figure 2: Strand exchange reactions enable reversible DNA–GNP swelling.

    a, Schematic (top) and detailed design (bottom) for reversible expansion and contraction of a DNA–GNP film. We note that our DNA–GNP film has no long-range order. (1) Active DNA–GNP domain composed of D (magenta) and C (red) particles with Linker DC (yellow), which has a 15-base-pair gap. (2) The gap in Linker DC is hybridized with Filler DC (orange), which results in the expansion of the DNA structure. (3) For reversible actuation, Filler DC can be removed by Stripper DC (light blue). b, Diagram for the hybridization equilibrium of three different states (black for (1), red for (2) and blue for (3)) in a by five different oligonucleotides: D, C, Linker DC, Filler DC and Stripper DC. Assuming the DNA–GNPs form (DC) with Linker DC, the calculations were conducted for examples without filler and stripper, with only filler, with only stripper, and with both filler and stripper. c, Qualitative analysis of the changes in thickness of a film composed of (DC)10. The thickness and normalized thickness for the film without Filler DC (red) and with Filler DC (black) are measured by ellipsometry (error bars show the standard deviation).

  3. Active–passive DNA–GNP films undergo sheet-to-tube shape transitions.
    Figure 3: Active–passive DNA–GNP films undergo sheet-to-tube shape transitions.

    a, Schematics for an active–passive DNA–GNP film composed of (AC)5(DC)5 where the AC domain is the active layer (green) and the DC domain is the passive layer (red). The AC domain was made either (i) with Filler AC or (ii) without Filler AC, respectively. b, Series of microscope images showing the fabrication of DNA–GNP films. After the monolithic DNA–GNP film was formed, the PDMS gasket was removed to leave a patterned DNA–GNP film on the substrate. Then, the films were liberated from the substrate by selective melting of the sacrificial AB domain in a 0.05 M PBS solution. Free-standing DNA–GNP films initially had tubular structures due to the different volume expansion between the AC and DC domains, but readily formed flat structures in a 0.3 M PBS solution. c, Schematics (top) and series of microscope images (bottom) for the programmed actuation of DNA–GNP films. Flat structures were actuated by adding (i) Stripper AC or (ii) Filler AC to form tubular structures where the (i) passive or (ii) active domains acted as an outer layer by (i) contraction or (ii) expansion of the active layer, respectively. The snapshots for (i) were taken for initial state (left), 15s (middle) after adding Stripper AC and 11s (right) after adding Filler AC, and for (ii) were taken for initial state (left), 44s after adding Filler AC (middle) and 36s (right) after adding Stripper AC. Scale bars, 500 µm in b and 200 µm in c.

  4. Dual-addressable DNA–GNP films explore a 2D configuration space.
    Figure 4: Dual-addressable DNA–GNP films explore a 2D configuration space.

    a, Schematics for a dual active DNA–GNP film composed of (AC)5(DC)5, where both the AC and DC domains are active layers. b, Time-lapse snapshots for the actuation of ten DNA–GNP films. Both AC and DC domains can have two different chemical states, expanded and contracted, which are denoted as superscripts, ex and c, respectively. Among ten (AC)ex/(DC)ex films, four films (green arrow) with an AC top and the rest of the films with DC tops were prepared (left). As Stripper AC was added, AC-topped films were actuated (middle) through operation 2, followed by the actuation of the DC-topped films (right) through operation 1. c, Series of microscope images for the actuation of a dual active DNA–GNP film. When the top AC layer (green) was contracted (top), contraction occurred throughout the entire surface of the layer, resulting in smooth curling to a tubular structure. When the bottom DC layer (red) was contracted (bottom), the periphery of the film contracted first (mid-bottom) and then it curled downwards to form a tubular structure. d, Complete actuation rule by a single DNA strand of a dual active DNA–GNP film. The four sections represent different chemical states, (AC)ex/(DC)ex (top left), (AC)c/(DC)ex(top right), (AC)ex/(DC)c(bottom left) and (AC)c/(DC)c (bottom right), where the superscripts ex and c indicate the expanded and contracted states, respectively. Actuation routes are indicated by the arrows. e, Snapshots for flip-flop actuation following operation 1–2–3–4. Scale bars, 500 µm in b and 200 µm in c,e.

  5. Double actuation of dual-addressable DNA–GNP films accesses unique shape states.
    Figure 5: Double actuation of dual-addressable DNA–GNP films accesses unique shape states.

    a, Diagram of the actuation rule by double DNA strands of a dual active DNA–GNP film. Dotted arrows indicate corresponding routes for dual actuation. b, Snapshots for flat-to-flat actuation through operation 5. In this operation, a mixture of Stripper AC and Stripper DC (with a 1:1 molar ratio) was added to an (AC)ex/(DC)ex film resulting in (AC)c/(DC)c. c, Snapshots for tube-to-tube actuation following operation 6. Tubular (AC)ex/(DC)c structures were actuated by a mixture of Filler DC and Stripper AC (with a 1:1 molar ratio) resulting in (AC)c/(DC)ex. d, Time-lapse snapshots for the actuation of ten DNA–GNP films. The shapes of all of the films changed from planar (left) to tubular (middle) as Stripper AC was added. When the mixture of the Filler AC and Stripper DC solution was then added, the tubular structures changed their curvature and curled along the short axis through operation 7. Scale bars, 200 µm in b,c and 500 µm in d.


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Author information

  1. Present address: Intel Corporation, Hillsboro, Oregon 97124, USA

    • Zaki G. Estephan


  1. Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA

    • Tae Soup Shim,
    • Zaki G. Estephan,
    • Jacob H. Prosser,
    • Daeyeon Lee &
    • John C. Crocker
  2. Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA

    • Tae Soup Shim,
    • Zaki G. Estephan,
    • Zhaoxia Qian,
    • David M. Chenoweth &
    • So-Jung Park
  3. Department of Chemical Engineering, Ajou University, Suwon 16499, Korea

    • Tae Soup Shim
  4. Department of Energy Systems Research, Ajou University, Suwon 16499, Korea

    • Tae Soup Shim
  5. Division of Advanced Materials, Korea Research Institute of Chemical Technology (KRICT), Daejeon 34114, Korea

    • Su Yeon Lee
  6. Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea

    • So-Jung Park


T.S.S., D.L., S.-J.P. and J.C.C. designed the study. T.S.S., Z.G.E., D.C. and J.C.C. designed the DNA sequence library. T.S.S., Z.Q. and S.Y.L. prepared the DNA–GNPs and other materials. T.S.S. and J.H.P. set up and performed the ellipsometry measurements. T.S.S. performed the experiments and prepared the figures. T.S.S., D.L., S.-J.P. and J.C.C. interpreted the results and wrote the paper.

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The authors declare no competing financial interests.

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