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Cited by 120Adhesion, Friction, and Surface InteractionsAdvanced Materials and MechanicsRobotic Locomotion and Control

Human climbing with efficiently scaled gecko-inspired dry adhesives

Open access
Hawkes, Elliot W., Eason, Eric V., Christensen, David L., Cutkosky, Mark R.·2015·Journal of The Royal Society Interface
DOI 10.1098/rsif.2014.0675PMC PMC4277072
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Abstract

Since the discovery of the mechanism of adhesion in geckos, many synthetic dry adhesives have been developed with desirable gecko-like properties such as reusability, directionality, self-cleaning ability, rough surface adhesion and high adhesive stress. However, fully exploiting these adhesives in practical applications at different length scales requires efficient scaling (i.e. with little loss in adhesion as area grows). Just as natural gecko adhesives have been used as a benchmark for synthetic materials, so can gecko adhesion systems provide a baseline for scaling efficiency. In the tokay gecko (Gekko gecko), a scaling power law has been reported relating the maximum shear stress σmax to the area A: σmax ∝ A(-1/4). We present a mechanical concept which improves upon the gecko's non-uniform load-sharing and results in a nearly even load distribution over multiple patches of gecko-inspired adhesive. We created a synthetic adhesion system incorporating this concept which shows efficient scaling across four orders of magnitude of area, yielding an improved scaling power law: σmax ∝ A(-1/50). Furthermore, we found that the synthetic adhesion system does not fail catastrophically when a simulated failure is induced on a portion of the adhesive. In a practical demonstration, the synthetic adhesion system enabled a 70 kg human to climb vertical glass with 140 cm(2) of adhesive per hand.

Integrity signals

Registry

Crossref · 10.1098/rsif.2014.0675

Cites

30 of 32 references verified0 citation errors · 2 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

2 of 22 cited sources checked · 2 supported · 0 flagged

  • Premisecitation

    Arraying adhesive material into elastically coupled sections tends to halt, divert and reinitiate the crack.

    “Another method is to array the adhesive material into elastically coupled sections [22,23], which tends to halt, divert and reinitiate the crack.”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [22] 22. Ge L, Sethi S, Ci L, Ajayan PM, Dhinojwala A. 2007 Carbon nanotube-based synthetic gecko tapes. Proc. Natl Acad. Sci. USA 104, 10 792-10 795. (doi:10. 1073/pnas.0703505104) source
    • cites [23] 23. Glassmaker NJ, Jagota A, Hui CY, Noderer WL, Chaudhury MK. 2007 Biologically inspired crack trapping for enhanced adhesion. Proc. Natl Acad. Sci. USA 104 10 786-10 791. (doi:10.1073/pnas. 0703762104) source
  • Findingown data

    The synthetic adhesion system does not fail catastrophically when a simulated failure is induced on a portion of the adhesive.

    “Furthermore, we found that the synthetic adhesion system does not fail catastrophically when a simulated failure is induced on a portion of the adhesive.”
    • Also stated in: § 1. Introduction · plain
      “Furthermore, the system was found to resist catastrophic failure by preventing stress concentrations when a simulated failure was induced on a portion of the adhesive (see §2.3)”
    Quote in the paperSubstantial claim
  • Findingreasoning

    Using degressive elements as suspensions for patches of adhesive results in a decrease in the variation in adhesive loads as displacements increase.

    “Using degressive elements as suspensions for patches of adhesive results in a decrease in the variation in adhesive loads as the displacements increase.”
    Quote in the paperSubstantial claim
  • Findingown data

    The synthetic adhesion system ensures that the load distribution across a large adhesive area is nearly uniform, using degressive load-sharing.

    “To achieve this goal, we developed a synthetic adhesion system which ensures that the load distribution across a large adhesive area is nearly uniform, using a concept referred to as degressive load-sharing.”
    • Also stated in: § 2.5. Adhesion system capabilities · plain
      “With these design features, the synthetic adhesion system was found to produce a nearly-uniform load distribution (figure 5)”
    Quote in the paperSubstantial claim
  • Findingown data

    The synthetic adhesion system enabled a 70 kg human to climb vertical glass with 140 cm^2 of adhesive per hand.

    “In a practical demonstration, the synthetic adhesion system enabled a 70 kg human to climb vertical glass with 140 cm 2 of adhesive per hand.”
    • Also stated in: § 2.5. Adhesion system capabilities · plain
      “Using this system, a human of mass 70 kg successfully ascended a 3.7 m vertical glass wall with 140 cm 2 of gecko-inspired dry adhesives in each hand (figure 2).”
    Quote in the paperSubstantial claim
  • Classified as probably not a substantial claim. 20
  • May combine two claims. 31
  • The quote only partly states this claim. 1

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Gecko adhesive has been observed to self-clean when it becomes contaminated.

    “however, gecko adhesive has been observed to self-clean when it becomes contaminated [26].”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [26] 26. Hansen WR, Autumn K. 2005 Evidence for self- cleaning in gecko setae. Proc. Natl Acad. Sci. USA 102, 385-389. (doi:10.1073/pnas.0408304102) source

  • May combine two claims.

    Findingown data

    Only a fraction of the adhesive area contacted the surface, and the load was not evenly distributed even in the areas that did make contact.

    “Only a fraction of the adhesive area contacted the surface, and the load was not evenly distributed even in the areas that did make contact.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The coefficient of variation of force distribution was roughly constant for progressive elements but significantly decreased near maximum extension for degressive elements.

    “The uniformity of the force distribution can be quantified by the ratio of the standard deviation to the mean, or coefficient of variation (CV), which was roughly constant for the progressive elements, but significantly decreased near maximum extension for the degressive elements (figure 5).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Force and displacement measurements from the 24-tile synthetic adhesion system show that average adhesive forces at maximum extension were 70% and 94% of the maximum force on any tile for progressive and degressive elements, respectively, in good agreement with the model.

    “Force and displacement measurements from the 24-tile synthetic adhesion system with progressive and degressive load-sharing elements (figure 4e) show that the average adhesive forces at maximum extension were 70% and 94% of the maximum force on any of the tiles, in good agreement with the model.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Near maximum load, the force distribution was non-uniform in the progressive case, with a few tiles carrying disproportionately high percentages of the load; on the other hand, the distribution became highly uniform in the degressive case near maximum load, with all of the tiles supporting nearly equal forces.

    “Near maximum load, the force distribution was non-uniform in the progressive case, with a few tiles carrying disproportionately high percentages of the load; on the other hand, the distribution became highly uniform in the degressive case near maximum load, with all of the tiles supporting nearly equal forces.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The CV remained constant at a moderate value (0.17-0.19) for the progressive elements as the load increased, but decreased significantly for the degressive elements (ending at 0.04).

    “The CV, equal to the ratio of the standard deviation to the mean (n ¼ 24), remained constant at a moderate value (0.17-0.19) for the progressive elements as the load increased, but decreased significantly for the degressive elements (ending at 0.04).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    With the degressive nitinol springs and with the same x and Q avg, the model predicts F max = 37 N and F avg = 36 N = 0.97 F max.

    “With the degressive nitinol springs and with the same x and Q avg , the model predicts F max ¼ 37 N and F avg ¼ 36 N ¼ 0.97 F max (figure 4d, solid blue lines).”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: The model used to create figure 4d involves an array of identical nonlinear springs loaded in parallel, where the initial displacements of the springs are distributed over some range.
    • The authors state this as an assumption: The function f(X) is linear over the range of possible values taken by X = x - Q_i.

  • May combine two claims.

    Findingreasoning

    Degressive load-sharing does not always ensure exactly equal loads, but it does ensure that all loads are limited to a safe level as long as the entire system is not overloaded.

    “While degressive load-sharing does not always ensure exactly equal loads, it does ensure that all loads are limited to a safe level as long as the entire system is not overloaded.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The synthetic adhesion system exhibits good scaling on surfaces with some curvature (r ≈ 200 m), in contrast to a simple single-tile mechanism.

    “The synthetic adhesion system also exhibits good scaling on surfaces with some curvature (r % 200 m; figure 9), in contrast to a simple single-tile mechanism.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingnone given

    At the displacement x = 4.6 mm, the average force F avg for the progressive springs was 70% of the maximum force F max, but 94% for the degressive nitinol springs.

    “At the displacement x ¼ 4.6 mm, the average force F avg for the progressive springs was 70% of the maximum force F max , but 94% for the degressive nitinol springs.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Using the progressive force-displacement curve of the nylon strand, equations (A 2) and (A 3) predict F max = 37 N and F avg = 27 N = 0.74 F max.

    “Using the progressive force -displacement curve of the nylon strand, equations (A 2) and (A 3) predict F max ¼ 37 N and F avg ¼ 27 N ¼ 0.74 F max (figure 4d, dashed red lines).”
    Quote in the paperNot a substantial claim
    • The authors state this as an assumption: The model used to create figure 4d involves an array of identical nonlinear springs loaded in parallel, where the initial displacements of the springs are distributed over some range.
    • The authors state this as an assumption: The function f(X) is linear over the range of possible values taken by X = x - Q_i.

  • May combine two claims.

    Findingown data

    On a curved surface (r ≈ 200 m), the synthetic system with area of 100 cm^2 performs at just under 80% of the performance of a 6.5 cm^2 tile on a flat surface, whereas a 100 cm^2 single tile achieves only approximately 15%.

    “On this curved surface, the synthetic system with area of 100 cm 2 performs at just under 80% of the performance of a 6.5 cm 2 tile on a flat surface, whereas a 100 cm 2 single tile achieves only approximately 15%.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The synthetic adhesion system using degressive load-sharing elements distributes loads uniformly and robustly.

    “We have shown that a synthetic adhesion system using degressive load-sharing elements distributes loads uniformly and robustly and allows efficient scaling of adhesives.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    Using rigid flat tiles avoids internal elastic stresses in the adhesive backing and allows nearly-complete contact area without stress concentrations when loaded on a flat surface.

    “Using rigid flat tiles avoids internal elastic stresses in the adhesive backing and allows nearly-complete contact area without stress concentrations when loaded on a flat surface (figure 8d-h).”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The intended climbing surface is relatively flat.

  • May combine two claims.

    Findingown data

    Pressure on the back of the tile did not increase the contact area, nor did the contact area decrease when the pressure was removed.

    “Pressure on the back of the tile (f ) did not increase the contact area, nor did the contact area decrease when the pressure was removed (g).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingnone given

    The adhesion system can attach and detach in less than a second.

    “(which can attach and detach in less than a second)”
    Quote in the paperNot a substantial claim

  • May combine two claims. The quote only partly states this claim.

    Findingown data

    The average forces F avg are 74% and 97% of the maximum force F max for the progressive and degressive cases, respectively.

    “The average forces F avg are 74% and 97% of the maximum force F max for the two cases.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    When the load in the tendon was removed, the contact area greatly decreased and the adhesive released from the surface.

    “However, when the load in the tendon was removed, the contact area greatly decreased and the adhesive released from the surface (h).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The real areas of contact (normalized to the compressed state) were 49.7%, 100%, and 35.3% for (a), (b) and (c), respectively.

    “The real areas of contact (normalized to the compressed state) were 49.7%, 100%, and 35.3% for (a), (b) and (c), respectively.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Findingnone given

    Keeping the load angles between 0° and 7° from vertical improves the maximum load that the PDMS microwedge adhesive can support.

    “This improves the maximum load that the PDMS microwedge adhesive can support.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Premisenone given

    In degressive load-sharing, elastic elements with decreasing stiffness with increasing displacement support independent patches of adhesive and help equalize the load on all patches.

    “In degressive load-sharing, elastic elements which have decreasing stiffness with increasing displacement support independent patches of adhesive and help equalize the load on all patches.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    PDMS microwedges exhibit controllable adhesion that can be switched on or off in a fraction of a second by applying a shear stress, making them especially suitable for climbing.

    “While other dry adhesive materials produce larger adhesive stresses, PDMS microwedges are especially suitable for climbing because they exhibit controllable adhesion that can be effectively switched on or off in a fraction of a second by applying a shear stress.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [4] 4. Day P, Eason EV, Esparza N, Christensen D, Cutkosky MR. 2013 Microwedge machining for the manufacture of directional dry adhesives. J. Micro Nano-Manuf. 1, 011001. (doi:10.1115/ 1.4023161) source
    • cites [5] 5. Parness A, Soto D, Esparza N, Gravish N, Wilkinson M, Autumn K, Cutkosky M. 2009 A microfabricated wedge-shaped adhesive array displaying gecko-like dynamic adhesion, directionality and long lifetime. J. R. Soc. Interface 6, 1223-1232. (doi:10.1098/rsif. 2009.0048) source

  • May combine two claims.

    Premisecitation

    PDMS slanted microwedges adhere well to glass and can be repositioned many times without degradation.

    “The adhesive chosen for this task consists of polydimethylsiloxane (PDMS) slanted microwedges (roughly 100 mm tall), which adhere well to glass and can be repositioned many times without degradation [4,5]”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [4] 4. Day P, Eason EV, Esparza N, Christensen D, Cutkosky MR. 2013 Microwedge machining for the manufacture of directional dry adhesives. J. Micro Nano-Manuf. 1, 011001. (doi:10.1115/ 1.4023161) source
    • cites [5] 5. Parness A, Soto D, Esparza N, Gravish N, Wilkinson M, Autumn K, Cutkosky M. 2009 A microfabricated wedge-shaped adhesive array displaying gecko-like dynamic adhesion, directionality and long lifetime. J. R. Soc. Interface 6, 1223-1232. (doi:10.1098/rsif. 2009.0048) source

  • May combine two claims.

    Premisecitation

    Stickybot had an area of adhesive that should have supported 5 kg based on small-scale tests, but could only support 500 g owing to inefficient scaling.

    “For instance, Stickybot had an area of adhesive that should have supported 5 kg based on smallscale tests, but could only support 500 g owing to inefficient scaling [11].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [11] 11. Kim S, Spenko M, Trujillo S, Heyneman B, Santos D, Cutkosky MR. 2008 Smooth vertical surface climbing with directional adhesion. IEEE Trans. Robot 24, 65 -74. (doi:10.1109/TRO.2007.909786) source

  • May combine two claims.

    Interpretationreasoning

    If all degressive elements are in the low-stiffness regime, the overall stiffness of the system is much lower, but there is no instability because the stiffness is still positive.

    “If all the elements are in the low-stiffness regime, the overall stiffness of the system is much lower, but there is no instability, because the stiffness is still positive.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    When the synthetic adhesion system reaches maximum extension, the stress distribution over the adhesive area is both uniform and maximized, ensuring efficient scaling.

    “Thus, when the synthetic adhesion system reaches maximum extension, the stress distribution over the adhesive area is both uniform and maximized, ensuring efficient scaling.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Load-sharing in gecko adhesion systems may not be ideal, which motivates the development of a synthetic system with improved load-sharing.

    “These results suggest that load-sharing in gecko adhesion systems may not be ideal, which motivates the development of a synthetic system with improved load-sharing.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationreasoning

    Such a collision could result in the contacted tile failing, and the failure would propagate.

    “Such a collision could result in the contacted tile failing, and the failure would propagate.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductreasoning

    The measured gecko stress distributions may have been influenced by the geckos' behaviour, stage in their moulting cycle, human handling or individual anatomical variations.

    “as it is possible that the measured stress distributions may have been influenced by the geckos' behaviour, stage in their moulting cycle, human handling or individual anatomical variations.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Recent work has shown that PDMS microwedges function in the environment of outer space.

    “Recent work has also shown that PDMS microwedges function in the environment of outer space [28]”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [28] 28. Parness A et al. 2013 Controllable on-off adhesion for Earth orbit grappling applications. In 2013 IEEE Aerospace Conf. New York, NY: IEEE. source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    An average adult male hand has a palmar surface area of about 140-170 cm2.

    “An average adult male hand has a palmar surface area of about 140-170 cm 2 [15].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [15] 15. Hsu YW, Yu CY. 2010 Hand surface area estimation formula using 3D anthropometry. J. Occup. Environ. Hyg. 7, 633-639. (doi:10.1080/15459624. 2010.514259) source

  • May combine two claims.

    Interpretationreasoning

    Maximum uniformity is achieved at maximum extension of the degressive elements, at which point a failure could potentially be catastrophic.

    “Maximum uniformity is achieved at maximum extension of the degressive elements, at which point a failure could potentially be catastrophic.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Because the highly loaded tiles did not experience a substantial increase in force, they did not become overloaded and the failure did not propagate.

    “Because the highly loaded tiles did not experience a substantial increase in force, they did not become overloaded and the failure did not propagate.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Study design and conductreasoning

    The gecko stress distribution results should be regarded as suggestive rather than conclusive.

    “These results should be regarded as suggestive rather than as conclusive”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisenone given

    The trend of decreasing adhesive capability with increasing area observed in the tokay gecko has not been fully explained.

    “The trend of decreasing adhesive capability with increasing area observed in the tokay gecko (figure 1) has not been fully explained.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductcitation

    The synthetic adhesion system uses adhesive patches mounted on rigid flat tiles that deviate from flatness by no more than the working distance of the PDMS microwedge adhesive features (35 mm) over the length of the tiles (2.5 cm), and the tiles are sufficiently rigid to maintain this flatness tolerance when loads are applied.

    “The adhesive patches are mounted on rigid flat tiles, which deviate from flatness by no more than the working distance of the PDMS microwedge adhesive features (35 mm) over the length of the tiles (2.5 cm); additionally, the tiles are sufficiently rigid to maintain this flatness tolerance when loads are applied [9].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [9] 9. Hawkes EW, Eason EV, Asbeck AT, Cutkosky MR. 2013 The gecko's toe: scaling directional adhesives for climbing applications. IEEE/ASME Trans. Mech. 18, 518-526. (doi:10.1109/TMECH.2012.2209672) source
    • Rests on an assumption: The intended climbing surface is relatively flat.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    A total displacement larger than x = 4.6 mm would result in tiles colliding in the case of one tile detaching from the surface while all the rest remain in contact.

    “x ¼ 4.6 mm is equal to the intertile spacing: a total displacement larger than this would result in tiles colliding in the case of one tile detaching from the surface while all the rest remain in contact.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationnone given

    The synthetic adhesion system may be able to outperform a gecko on relatively flat, smooth and clean vertical glass.

    “Second, while the synthetic adhesion system may be able to outperform a gecko on relatively flat, smooth and clean vertical glass”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisenone given

    A branched tendon design allows the transfer of load solely through tension, without requiring compressive or bending elements, which could prevent a structure from conforming to non-flat surfaces.

    “Such a branched design allows the transfer of load solely through tension, without requiring compressive or bending elements, which could prevent a structure from conforming to non-flat surfaces.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    For a system of adhesive tiles loaded through independent degressive elements, if an adhesive tile fails, the combined load on the other tiles must increase to compensate, but this stress increase is not necessarily concentrated in the area surrounding the failure.

    “On the other hand, a different situation occurs for a system of adhesive tiles loaded through independent degressive elements.If an adhesive tile fails, the combined load on the other tiles must increase to compensate for the decrease in area.However, this stress increase is not necessarily concentrated in the area surrounding the failure.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisereasoning

    On contaminated surfaces, even geckos have trouble producing adhesion.

    “On contaminated surfaces, even geckos have trouble producing adhesion (van der Waals forces require intimate contact between the surface and the adhesive)”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    For degressive load-sharing to function correctly, these limits must be preset according to the maximum adhesion attainable on the intended combination of adhesive and adherend surface.

    “For degressive load-sharing to function correctly, these limits must be preset according to the maximum adhesion attainable on the intended combination of adhesive and adherend surface.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Premisenone given

    It has been suggested that this is partially caused by a reduction in contact area or unequal load-sharing between or within lamellae, but no measurements supporting this have been presented.

    “It has been suggested that this is partially caused by a reduction in contact area or unequal load-sharing between or within lamellae [6,29], but no measurements supporting this have been presented.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [6] 6. Autumn K. 2006 Properties, principles and parameters of the gecko adhesive system. In Biological adhesives (eds AM Smith, JA Callow), pp. 225-256. Berlin, Germany: Springer. source
    • cites [29] 29. Bullock JM, Federle W. 2011 Beetle adhesive hairs differ in stiffness and stickiness: in vivo adhesion measurements on individual setae. Naturwissenschaften 98, 381-387. (doi:10.1007/ s00114-011-0781-4) source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The technique of FTIR has been used to measure the area of contact of gecko-inspired adhesives.

    “This technique has been used to measure the area of contact of gecko-inspired adhesives [30].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [30] 30. Lee J, Fearing RS, Komvopoulos K. 2008 Directional adhesion of gecko-inspired angled microfiber arrays. Appl. Phys. Lett. 93, 191910. (doi:10.1063/1. 3006334) source

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    All animal testing was done at CiBER in full compliance with the regulations of UC Berkeley.

    “All animal testing was done at the Center for Interdisciplinary Bio-inspiration in Education and Research (CiBER) in full compliance with the regulations of UC Berkeley.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductreasoning

    While the human interaction in the test adds uncertainty, it was necessary, because the gecko's body weight was not large enough to test the limits of its adhesive.

    “While the human interaction in the test adds uncertainty, it was necessary, because the gecko's body weight was not large enough to test the limits of its adhesive”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: The gecko's body weight was not large enough to test the limits of its adhesive.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    A similar method has been previously reported.

    “furthermore, a similar method has been previously reported [1].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [1] 1. Autumn K et al. 2002 Evidence for van der Waals adhesion in gecko setae. Proc. Natl Acad. Sci. USA 99, 12 252-12 256. (doi:10.1073/pnas. 192252799) source
47 of 47

  • The paper relies on this without support.

    The intended climbing surface is relatively flat.

    “Because we know, a priori, that our intended climbing surface is relatively flat, we are able to include compressive and bending elements to make all of the tendons parallel (figure 7c).”

  • The paper relies on this without support.

    The climber's surface area and mass follow a square-cube law.

    “This is partly because the area of adhesive required for climbing increases disproportionately as the scale increases (even with perfectly efficient scaling) owing to the climber's surface area and mass following a square-cube law.”

  • The paper relies on this without support.

    The distance between lamellae is only 500-600 mm for the tokay gecko.

    “The distance between lamellae is only 500-600 mm for the tokay gecko”

  • The authors state this as an assumption.

    The model used to create figure 4d involves an array of identical nonlinear springs loaded in parallel, where the initial displacements of the springs are distributed over some range.

    “The model used to create figure 4d involves an array of identical nonlinear springs loaded in parallel, where the initial displacements of the springs are distributed over some range.”

  • The authors state this as an assumption.

    The function f(X) is linear over the range of possible values taken by X = x - Q_i.

    “Assuming the function f(X ) is linear over the range of possible values taken by X ¼ x -Q i , then”

  • The paper relies on this without support.

    The gecko's body weight was not large enough to test the limits of its adhesive.

    “the gecko's body weight was not large enough to test the limits of its adhesive”
6 of 6

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Authors
Hawkes, E. W., Eason, E. V., Christensen, D. L., & Cutkosky, M. R.
Affiliations
Stanford University (US)
Corresponding author
Hawkes, Elliot W.
ORCID
Venue
Journal of The Royal Society Interface
Publisher
The Royal Society
Published
2015-01
Volume
12
Issue
102
Pages
20140675
ISSN
  • 1742-5662 (ISSN-L)
  • 1742-5689
DOI
10.1098/rsif.2014.0675
PMC
PMC4277072
OpenAlex
W1993017363
Cited by
120
References
30
Citations by year
2026: 7 · 2025: 7 · 2024: 6 · 2023: 13 · 2022: 10 · 2021: 15 · 2020: 6 · 2019: 9 · 2018: 14 · 2017: 8 · 2016: 14 · 2015: 11
FWCI
11.38
Type
journal article
Language
en
Open access
Licence
royalsociety.org/journals/ethics-policies/data-sharing-mining/ (tdm)
Locations
  • Journal of The Royal Society Interface (publishedVersion)
  • Europe PMC (PubMed Central) (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • National Science Foundation
  • Defense Advanced Research Projects Agency (HR0011-12-C-0040)
Topics
  • Physical Sciences › Engineering › Mechanics of Materials › Adhesion, Friction, and Surface Interactions
  • Physical Sciences › Engineering › Mechanical Engineering › Advanced Materials and Mechanics
  • Physical Sciences › Engineering › Biomedical Engineering › Robotic Locomotion and Control
Keywords
gecko-inspired adhesives, dry adhesion, load sharing, non-uniform load distribution, shear stress, Tokay gecko, synthetic adhesives, vertical climbing, fault tolerance, rough surface adhesion
MeSH terms
Adhesiveness, Adhesives, Animals, Dimethylpolysiloxanes, Elasticity, Humans, Lizards, Movement, Stress, Mechanical, Models, Animal, Biomimetics, Shear Strength

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-11.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-11.

Cited sources are checked by gpt-6-sol.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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