基于表面起皱法的梯度图案的可控制备

报道了基于非刻蚀法的表面起皱机制来实现高分子薄膜表面的周期性梯度图案的简单可控制备.即对于处于机械拉伸状态的聚二甲基硅氧烷(PDMS)弹性基底,在其底部垫入"积木",而后对其进行紫外-臭氧(UVO)和氧等离子体(OP)的联合表面处理."积木"的加入引起了表面处理后表面硅氧层(SiOx)梯度厚度的形成,进而当释放拉伸应变后,诱导产生了梯度皱纹图案.结果表明:当UVO与OP联用处理时,不仅实现了较小拉伸应变下梯度皱纹形貌的制备,而且扩大了UVO单独使用时梯度皱纹周期的变化范围.通过OP与UVO的处理顺序和处理时间等因素的简单调节,进一步实现了不同梯度皱纹微结构的精细构筑.

Controlled Fabrication of Gradient Patterns Based on Surface Wrinkling

We reported a simple method to fabricate gradient patterns on polymer-based films,which was based on the non-lithographic surface wrinkling.Namely,a polydimethylsiloxane (PDMS) soft substrate was mechanically pre-strained with a "triangular block" beneath the strained PDMS sheet,followed by surface oxidation with ultraviolet ozone (UVO) and/or oxygen plasma (OP).A thin silica-like (SiOx) stiff layer was generated after the surface oxidization.Thus the surface wrinkling was induced on the as-formed film/substrate system of SiOx/PDMS bilayer when the pre-strain of the PDMS substrate was released slowly.It was found that aligned surface wrinkles with a uniform wavelength were yielded on the OP-exposed PDMS substrate.However,gradient patterns were obtained when the PDMS substrate was treated by UVO.The introduction of the "triangular block" beneath the strained PDMS sheet led to a change of the distance between the PDMS substrate and the UVO light,and thus an increased decay of UVO light intensity along with the exposed PDMS sheet happened.As a result,the gradient thickness of the SiOx layer was formed on the resulting SiOx/PDMS bilayer and the corresponding gradient wrinkles were generated,since the wrinkle wavelength was closely related to the thickness of the stiff film.In contrast,the thickness of the as-formed SiOx layer was uniform during the OP exposure.It was noted that,for the single UVO exposure,a large pre-strain was required to induce the surface wrinkling on the UVO-exposed PDMS substrate.Interestingly,compared with the single UVO treatment,the combined UVO/OP surface oxidation treatment (e.g.,UVO-OP and OP-UVO treatment) did not need the large pre-strain on the PDMS substrate.Furthermore,the wavelength range of the obtained gradient wrinkles was extended greatly.Consequently,different gradient patterns with well-defined microstructures were finely tuned by a simple manipulation of the exposure order and the exposure duration of the combined UVO/OP applied to the pre-strained PDMS substrate.Based on the systematical results,we revealed the underlying physics that was related to the formation of the current gradient wrinkle patterns.