Controlled mud-crack patterning and self-organized cracking of polydimethylsiloxane elastomer surfaces

Abstract

Exploiting pattern formation – such as that observed in nature – in the context of micro/nanotechnology could have great benefits if coupled with the traditional top-down lithographic approach. Here, we demonstrate an original and simple method to produce unique, localized and controllable self-organised patterns on elastomeric films. A thin, brittle silica-like crust is formed on the surface of polydimethylsiloxane (PDMS) using oxygen plasma. This crust is subsequently cracked via the deposition of a thin metal film – having residual tensile stress. The density of the mud-crack patterns depends on the plasma dose and on the metal thickness. The mud-crack patterning can be controlled depending on the thickness and shape of the metallization – ultimately leading to regularly spaced cracks and/or metal mesa structures. Such patterning of the cracks indicates a level of self-organization in the structuring and layout of the features – arrived at simply by imposing metallization boundaries in proximity to each other, separated by a distance of the order of the critical dimension of the pattern size apparent in the large surface mud-crack patterns.

A skin-attachable, stretchable integrated system based on liquid GaInSn for wireless human motion monitoring with multi-site sensing capabilities

“…In the fabrication process, Cr and Au were deposited on partially cured PDMS substrates to avoid cracking that tends to occur with fully curved substrates. 28,29 Detailed descriptions of the fabrication process appear in the experimental section in Note S1 (Supplementary Information), as well as in Supplementary Figures S3 and S4. A slightly wavy surface was obtained after the Cr/Au deposition process, as shown in Figure 2e, but at a level that was possible to pattern using photolithography and wet etching.…”

“…Deposition of the metal film by sputtering or e-beam evaporation may crack the film surface due to residual strain generated during the film formation process. 28,29 Therefore, in this study, the Cr/Au film layer was deposited on a partially cured PDMS substrate. The optical images of the PDMS/Cr/Au surface are presented in Supplementary Figure S3.…”

Controlled Mechanical Cracking of Metal Films Deposited on Polydimethylsiloxane (PDMS)

“…Brittle devices can be placed close to the cracks, so external strain will not damage them. Former approaches avoided cracking in local islands [13,23]. However, a stretchable large-area connection technology remains a challenge [14].…”

“…Cracks always appear first in the most brittle areas [23,24,25]. This typically means that the thin films with electronic functionality, i.e., metals, dielectrics, or semiconductors, crack, while the softer environment stays unaffected.…”

Gold Layers on Elastomers near the Critical Stress Regime

“…A major goal is the development of nanometer‐thin flexible and stretchable electrodes for a few micrometer‐ or sub‐micrometer‐thin DEAs. Many materials and related fabrication and characterization methods have been proposed for electrodes, including carbon powder, metallic thin films, or the implantation of metal nanoclusters . Another approach to stretchable electronics, presented by Hirsch et al, is based on biphasic AuGa 2 /Ga solid–liquid thin metal films.…”