Supporting Information

Transcription

1 Electronic Suppleentar Material (ESI) for Soft Matter. This journal is The Roal Societ of Cheistr 07 Supporting Inforation Controllable Curvature fro Planar Poler Sheets in Response to Light Aber M. Hubbard, Russell W. Mailen, Mohaed A. Zikr, Michael D. Dicke*, and Jan Genzer* Aber M. Hubbard, Prof. Michael D. Dicke, Prof. Jan Genzer Departent of Cheical and Bioolecular Engineering NC State Universit Capus Bo 7905 Raleigh, NC U.S.A. Russell W. Mailen, Prof. Mohaed A. Zikr Departent of Mechanical and Aerospace Engineering NC State Universit Capus Bo 790 Raleigh, NC U.S.A Equal contributions to the paper; authors listed in alphabetical order. Figure SA depicts the saple fabrication process. Pre-strained polstrene sheets, coerciall available as Grafi shrink fil, were printed with black ink using a desktop, inkjet printer. The patterns were cut fro the sheet using scissors and placed in the center of a hot plate set to 90 C. An IR light stationed ~ 5 c above the surface of the saple was then turned on, and the subsequent saple shrinkage resulted fro localized absorption of the IR light b the patterned regions. The folded saples were iaged with a Canon EOS Rebel T3 DSLR caera fro the top down after reoval of the IR light stiulus (see far right iage in Figure SA). These iages were processed b an edge detection algorith in MATLAB. Figures SB,C depict an eaple inputted iage and the algorith output, respectivel. For deonstrative purposes the used iages are of a hen-and-chicks succulent plant, part of the Crassulaceae fail. This plant ehibits ultiple radii of curvature in various portions of the structure, as depicted b the two red circles outlined on Figure SC.

2 Figure S. (A) A step-b-step process depicting the eperiental saple preparation and recover processes. The saple designs were printed onto the polstrene sheets and cut out using scissors. The saples were eposed to an IR source which locall heats the saple and causes it to shrink and defor. (B) A saple iage of a plant with ultiple different radii of curvature that was analzed b a MATLAB edge detection algorith with the resulting iage (C) highlighting two distinct R c (depicted b red circles) found throughout the structure. The scale bar is 5. The aount of IR energ absorption depends upon the distribution and darkness of ink placed onto the saple. Figure SA shows the relationship between ink darkness, teperature, and IR absorption. The top row of Figure SA depicts a linear gradient in ink darkness across the length of the saple, identical to the pattern shown in Figure 5B. The second iage shows teperature results captured with an FLIR SC300 Series caera. This iage is scaled to the sae size as the ink pattern and is aligned with a plot of absorption and surface teperature

3 shown in the botto row of Figure SA. At 00% darkness, the ink coverage on our saples is never trul 00% due to liitations in the printing capabilities of an inkjet printer. Instead, the aiu ink coverage was eperientall found to reach a aiu of ~ 70% coverage which was then used to noralize our noinal ink densit values. The noralized absorption values were collected via Ultraviolet/Visible Spectroscop and recorded as an average absorption percentage across the n wavelength range for saple sets (ranging fro 0 % to 00 % noinal ink densit). These results were gathered in triplicate. Further inforation regarding the absorption of IR light b the inked surface has been previousl reported. The surface teperature values correspond to data gathered in the EaineIR software with the use of the theral caera. To deonstrate the agreeent of this heating behavior with coputational results, a saple structure is depicted in Figure SB which corresponds to the anticlastic structure seen in Figure. The regions with ink patterning are heated to teperatures eceeding the activation teperature (T a ~ T g ). Videos S-S, available online, deonstrate the recover response of the snclastic and anticlastic eperiental saples, respectivel, fro Figure in real tie. The red lighting seen in these videos is due to the IR lap and the silver background is aluinu foil placed over the face of the hot plate. Video S3, available online, deonstrates a saple with the direct echanis of curvature (a gradient in ink darkness) for the 3: aspect ratio substrate in real tie.

4 Figure S. A graphical and visual depiction of how surface teperature and noralized IR absorption increases with noinal and actual ink densit for eperiental (A) and coputational (B) results. The teperature values used within the graph are directl correlated to the values on the theral iage (A). The dashed black lines overlaid on the IR iage visuall depict that the surface teperature values weree recorded at the centerline (squares) and lower edge (circles). The lower iage in B representss the ink pattern where the gre regions are unpatterned and the black regions indicate ink coverage. In Figure 4, saples thatt reflect the indirect echanis of curvature are shown for three aspect ratios. A siilar stud was perfored for the direct curvature echanis saples presented in Figure 5A-C. The eperiental results for the threee aspect ratios are shown in

5 Figure S3. Siilar to the indirect curvature saples, saples with higher aspect ratios had a larger overall deforation with siilar radii of curvature due to the increase in the overall length of aterial. A siilar trend was observed as the aspect ratio was changed for each pattern. Figure S3. An illustration of the effects of changes to the saple aspect ratio while aintaining the designated gradient pattern. Saples becae ore curved with the increase in aspect ratio, while the sae general trend was observed for each gradient ink pattern. The scale bar is 5 for 3: aspect ratio saples and 0 for the : and : aspect ratio saples. A serial sectioning technique (cf. Figure S4A) was eploed to deonstrate the ecellent qualitative agreeent between the coputational and eperiental results. The saples were painted for increased contrast and are ibedded within a clear polester casting resin. The resulting round, puck-like structure was illed through in ~ 0.5 segents and digitall iaged between each illing step. The MATLAB edge detection algorith, discussed for Figure SB,C, was applied to each iage, and data points were gathered between each segent to generate a coplete digital, 3D point cloud for the eperiental saples as seen in Figures S4B,C. Note that the illing arks can still be seen for the outputted iage of the edge

6 detection algorith, but onl points on the saple were selected anuall to produce the final 3D representation. A gradient in color was assigned to the point cloud as a visual representation for changes in height. The coputational odel was overlaid in black onto the eperiental point cloud and deonstrates the ecellent agreeent. Videos S4-S5 available online show the point cloud results for the bordered (indirect curvature) and gradient (direct curvature) saples, Figure 6B and C respectivel, fro various angles for increased clarit. Figure S4. Serial section process used to obtain the digital, 3D point cloud of the bio-inspired structures. (A) The saples were painted, casted, illed in ~ 0.5 segents, and digitall iaged to acquire the necessar data points. The final point cloud can be seen for both the (B) indirect and (C) direct echanis of curvature. The gradient in color corresponds to changes in height while the black data points represent the coputational results. The radius of curvature (R c ) in quantitativel analzed saples was calculated b selecting three points fro the outputted MATLAB edge detection algorith graph, siilar to the plot seen in Figure SC and depicted in Figure 7A. The coordinates i and i for each of the three data points were entered into Equations S S4 below

7 Slope (S) 3 3 ) ( ) ( ) ( X C (S) X Y C C (S3) C C C Y X R (S4) where and are the slopes between the three chosen locations. The pertinent variables are visuall defined in Figure S5. The R c was calculated for both the coputational and eperiental saples, averaged across ~ 6 panels for each saple design. As seen in Figure 7, there is ecellent quantitative agreeent between the coputational and eperiental results with soe slightl elevated standard deviation values due to previousl entioned eperiental factors.

8 Figure S5. Scheatic defining variables in Equations S-S4. Supporting Inforation References: Ying Liu, Julie K. Boles, Jan Genzer and Michael D. Dicke, Soft Matter, 0, 8, 6.. Y. Liu, R. Mailen, Y. Zhu, M. D. Dicke and J. Genzer, Phs. Rev. E, 04, 89, 0460.