اثر میکروتوپوگرافی سطحی بر ترشوندگی فیلم پلی‌دی‌متیل‌سیلوکسان: ابرآب‌گریزی

نوع مقاله : پژوهشی

نویسندگان

تبریز، شهر جدید سهند، دانشگاه صنعتی سهند، دانشکده مهندسی پلیمر، کد پستی 5331817634

چکیده

فرضیه: پیشرفت‌های اخیر در میکرو و نانوفناوری امکان ایجاد سطوح میکرو یا نانوساختار کاربردی با ویژگی میکرو و نانوتوپوگرافی سطحی را فراهم می‌کند که می‌توانند خواص چسبندگی کمی را نشان دهند. دسته بسیار مهمی از این ساختارها، سطوح ابرآب‌گریز بوده که به‌شدت دافع آب هستند. در کار حاضر، اثرهای میکروتوپوگرافی سطحی بر رفتار ترشوندگی فیلم لاستیک پلی‌دی‌متیل‌سیلوکسان (PDMS) با هدف ایجاد سطح ابرآب‌گریز بررسی شده است.
روش‌ها: آرایه‌هایی از الگوی میکروستون‌ها با الهام از ساختارهای زیستی موجود در طبیعت با استفاده از روش میکرولیتوگرافی نرم و با نسبت‌های مختلف از گام به پهنا روی سطح PDMS ایجاد شد. به همین دلیل قالب‌هایی با استفاده از روش‌های میکروساخت و لیتوگرافی نوری ساخته شد. الگوی قالب‌ها بر اساس طرح ستون‌های وارونه بوده و با استفاده از حکاکی ناهمسانگرد سطح ویفر سیلیکون (روش حکاکی یون واکنشی عمیق، DRIE) به دو صورت قالب سیلیکونی با نسبت منظر بزرگ و قالب نورمقاوم با نسبت منظر کوچک، تهیه شد.
یافته‌ها: میکروستون‌های ساخته‌شده روی قالب سیلیکون دارای موج‌های نانومقیاسی بودند که ناشی از مراحل چندگانه حکاکی و اثرناپذیرسازی دیواره‌های جانبی در فرایند DRIE است. مهرهای لاستیکی نسخه‌های عینی از قالب بوده (نسخه‌های منفی) و از رزین PDMS قالب‌گیری شدند. مهرهای سیلیکونی آرایه‌های منظمی از برخی ویژگی‌های برجسته بودند که امکان انتقال الگو روی زیرلایه هدف را طی فرایند چاپ میکروتماسی فراهم می‌آورد. شکل‌دهی نسبت‌های متعدد گام میان ستون‌ها به پهنای آن‌ها برای بهینه‌سازی ارتباط بین توپوگرافی سطحی و رفتار ترشوندگی فیلم PDMS با استفاده از اندازه‌گیری‌های زاویه تماس ایستا آب انجام شد. در پژوهش حاضر، این ساختارها به خواص آب‌گریزی لاستیک سیلیکون ارتباط داده شد و برای الگوهای مختلف سطحی، انتقال از حالت مدل مرکب (Cassie-Baxter) به مدل تر (Wenzel) شناسایی شد. مشاهده شد، زاویه تماس وابسته به نوع شکل‌دهی میکروستون‌ها در انتقال از مدل Cassie-Baxter به مدل Wenzel در اندازه گام 60mm~ قرار می‌گیرد.   

کلیدواژه‌ها


عنوان مقاله [English]

Effects of Surface Microtopography on Wettability of Poly(dimethylsiloxane) Film: Superhydrophobicity

نویسندگان [English]

  • Shayesteh Khakvand
  • Kiyumars Jalili
  • Fatemeh Hassanpour
  • Farhang Abbasi
Faculty of Polymer Engineering, Sahand University of Technology, New Town of Sahand, Postal Code 5331817634, Tabriz, Iran
چکیده [English]

Hypothesis: Recent advances in micro- and nanotechnology have led to possible design of functional micro/nanostructured surfaces with micro/nanotopography features that can exhibit low adhesion properties. An important example of such structures is superhydrophobic surface, which is extremely water repellent. In the present work, the effects of surface microtopography on the wetting of poly(dimethylsiloxane) (PDMS) rubber film with the goal of producing superhydrophobic surface are investigated.
Methods: Micropillar arrays inspired by biological structures found in nature are produced on PDMS surface using a soft microlithography technique with different pitch/width ratios. To this end, the masters are fabricated using conventional microfabrication techniques and photolithography. Master designs tested are inverted pillar shape fabricated by anisotropic etching of silicon (reactive-ion etching, DRIE), a high aspect ratio master and a low aspect ratio photoresist master.
Findings: Our fabricated pillars have nano-scale ripples that arise from the series of alternating, independent silicon etching and sidewall passivation steps used in the DRIE process. The elastomeric stamps are negative replicas of the masters and they are fabricated by PDMS. The stamps have a regular array of protruding features, in order to make a pattern transfer to the target substrate during m-contact printing. Several pitch/width ratios are configured to optimize the relationship between surface topography and wetting behavior of PDMS film using static water contact angle measurements. We have correlated these structures with PDMS rubber hydrophobicity and have also characterized the transition from the composite (Cassie-Baxter) to wetted (Wenzel) states for different types of surface structures. The surface topography-dependent contact angle of water underwent a transition from Cassie-Baxter to Wenzel states at pitch size ~60 mm.

کلیدواژه‌ها [English]

  • PDMS rubber
  • superhydrophobicity
  • surface microtopography
  • soft lithography
  • reactive-ion etching
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