Spontaneous Self‐Folding in Confined Ultrathin Polymer Gels

Singamaneni, Srikanth; McConney, Michael E.; Tsukruk, Vladimir V.

doi:10.1002/adma.200903052

Cited by 40 publications

(42 citation statements)

References 51 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The growth of the folded structures is arrested when the surrounding regions of the residual gel surface layer become too thin (ϳ20 nm) to further shear (due to the strong anchoring to the substrate). 53 The folded structures evolve via a series of fast and discrete "popping" steps. The intersection points guide the drying-induced folding and sudden release from substrate, which is evident by the majority of the intersections lying on top of the hinge side instead and not underneath the hinge-side of the buckle.…”

Section: Resultsmentioning

confidence: 99%

Swelling-Induced Folding in Confined Nanoscale Responsive Polymer Gels

2010

Self Cite

View full text Add to dashboard Cite

Mechanical instabilities such as buckling, wrinkling, creasing, and folding are commonplace in both natural and synthetic systems over a wide range of length scales. In this study, we focus on the spontaneous folding behavior of the highly swellable confined nanoscale (thickness below 100 nm) gel films resulting in the formation of a network of regularly folded structures spontaneously emerging in the course of their swelling and drying. We suggest that regular self-folding is originated from periodic instabilities (wrinkles) caused by swelling-initiated stresses under confined conditions. Furthermore, folded gel structures can be organized into regular serpentine-like manner by imposing various boundary conditions on microimprinted surfaces. We suggest that this demonstration of uniform gel to mechanically mediate morphogenesis has far-reaching implications in the creation of complex, large-area, 3D gel nanostructures.

show abstract

Section: Resultsmentioning

confidence: 99%

Swelling-Induced Folding in Confined Nanoscale Responsive Polymer Gels

2010

Self Cite

View full text Add to dashboard Cite

show abstract

“…These authors did not report on the dynamics of the foldformation process, thus it is not clear whether the sequence of events was identical to that shown in Figure 1 and discussed above. Nevertheless the AFM images of the final structure 27,28 bear a striking resemblance to the folds seen here, especially to Supporting Information Figure S3, suggesting that similar phenomena may be at work. While Singamaneni et al 27,28 have not fully elucidated the mechanism of fold formation, they suggest that the folds originate from creases and preserve the original geometric characteristics of the creases.…”

mentioning

confidence: 79%

“…Nevertheless the AFM images of the final structure 27,28 bear a striking resemblance to the folds seen here, especially to Supporting Information Figure S3, suggesting that similar phenomena may be at work. While Singamaneni et al 27,28 have not fully elucidated the mechanism of fold formation, they suggest that the folds originate from creases and preserve the original geometric characteristics of the creases. In contrast, our results show that creases do not transform into folds, and indeed Case 6 in Table 1 shows that folds can arise even without creases.…”

mentioning

confidence: 79%

“…We have observed swelling-induced delamination and folding in films ranging from 250 to 6 μm thickness. If Singamaneni's observations 27,28 on 90−20 nm thick films are also attributable to the same mechanism, it would indicate that the delamination/folding phenomenon scales 4 orders of magnitude. Accordingly, it may prove useful for fabricating highaspect ratio surface features across a wide range of length-scales.…”

mentioning

confidence: 99%

“…Singamaneni et al 27,28 examined poly-2-vinylpyridine (P2VP) gel films ranging from 20 to 90 nm thick that were spuncoated onto silica surfaces and exposed to acidic conditions. Film swelling led to large amplitude folds which were observed by AFM imaging.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Swelling-Induced Delamination Causes Folding of Surface-Tethered Polymer Gels

Velankar

Lai

Vaia

2012

ACS Appl. Mater. Interfaces

View full text Add to dashboard Cite

When a polymer film that is weakly attached to a rigid substrate is exposed to solvent, swelling-induced compressive stress nucleates buckle delamination of the film from the substrate. Surprisingly, the buckles do not have a sinusoidal profile, instead, the film near the delamination buckles slides toward the buckles causing growth of sharp folds of high aspect ratio. These folds do not result from a wrinkle-to-fold transition; instead, the film goes directly from a flat state to a folded state. The folds persist even after the solvent evaporates. We propose that patterned delamination and folding may be exploited to realize high-aspect ratio topological features on surfaces through control of a set of boundary constraints arising from the interrelation of film-surface adhesion, film thickness and degree of swellabilty. KEYWORDS: folds, delamination, creases, buckles, wrinkles, swelling The swelling of polymers with solvent can lead to one class of such buckling phenomena in which an osmotic stress applied to a homogeneous body leads to nonhomogeneous deformation.10−12 One of the simplest geometries in which this can happen is the swelling of a cross-linked polymer film that is attached to a rigid substrate. If the extent of swelling is sufficiently large, the film swells nonhomogeneously and the free surface develops cusp-like creases and rounded wrinkles.12−15 Recent research 13,16 has clarified the mechanism of crease formation: lateral film swelling (i.e., swelling perpendicular to the film normal) is constrained by the rigid substrate, and hence the free surface of the film is under compressive stress. It is this compression that induces the creasing instability at the free surface. In this paper, we show that a new buckling phenomenon can also occur in the same situation: if the film is not strongly bound to the rigid substrate, a second kind of buckling instability can lead to large scale folding of the film. This Letter describes the basic phenomenon, clarifies the conditions under which folding does or does not occur, and proposes a schematic model for the process.Experiments were conducted using PDMS (Sylgard 184) films swollen with toluene. Sylgard is a two-part silicone rubber formulation in which the base resin and the cross-linker are usually mixed in a 10:1 ratio. For most of our experiments however, the ratio of the base resin to cross-linker was 10:0.4 which resulted in a lower cross-link density. The shear modulus of these films was 18 kPa (in contrast to 54 kPa for 10:1 ratio), and the films swelled 380% by weight with toluene.17 Films were prepared by spincoating the PDMS mixture onto acrylic sheets, letting them cross-link overnight, and then completing the cross-linking reaction for one hour at 75°C. Film thickness was measured with a profilometer at three locations on the spincoated films. Thickness variation was less than 15%. Sections of the films, roughly 25 × 25 mm in size were peeled off the acrylic sheets and carefully placed (without entrapping air bubbles) on glass slide...

show abstract

Amorphous and Poorly Ordered Polymers

Tsukruk

Singamaneni

2011

Scanning Probe Microscopy of Soft Matter

View full text Add to dashboard Cite

Spontaneous Self‐Folding in Confined Ultrathin Polymer Gels

Cited by 40 publications

References 51 publications

Swelling-Induced Folding in Confined Nanoscale Responsive Polymer Gels

Swelling-Induced Folding in Confined Nanoscale Responsive Polymer Gels

Swelling-Induced Delamination Causes Folding of Surface-Tethered Polymer Gels

Amorphous and Poorly Ordered Polymers

Contact Info

Product

Resources

About