PDMS機械性質檢測、力學模型建立與其在細胞力學方面的應用

Modeling and Characterization of Polydimethylsiloxane (PDMS) Pillar Arrays for Biological Applications

廖彥鳴(Yen-Ming Liao) ； 歐廣順(Kuang-Shun Ou) ； I-Kuan Lin ； 陳國聲(Kuo-Shen Chen)

《科儀新知》 182期 (2011/06) Pp. 12-20

https://doi.org/10.29662/IT.201106.0002

摘要

聚二甲基矽氧烷是微機電製程中之重要材料，廣泛地應用於奈米壓印以及生醫檢測等方面。藉由該材料所構建之微柱陣列的變形來量測及反推估細胞成長時與基材間之作用力，是近年來相當受到重視的生醫檢測技術之一。該方法首先藉由量測微柱之變形，接著以材料力學之懸臂樑公式，將所量測之變形量轉成作用力。然而，過雲的研究多將聚二甲基矽氧烷視為線性彈性材料，並且利用長樑理論下之材料力學公式進行轉換。由於聚二甲基矽氧烷屬黏彈材料，而一般微柱陣列之寬高比又遠小於長樑公式之可適用範園，這讓我們相信目前通用之轉換模型存在著相當大的誤差。因此，發展一套較精確之轉換模型有其必要性。本文同時從材料測試與分析模擬兩方向著手，分別對於聚二甲基矽氧烷於長尺度與微尺度下進行鬆弛與動態實驗以及相關之非線性有限元素分析，並實際製作微柱陣列進行實驗、模擬交叉比對與驗證，最後獲得一改良形變至作用力的模型。相信封評估細胞成長之作用力有相當的貢獻。

並列摘要

The mechanical interaction force between cells and their neighboring extracellular matrix is believed to be very important in various physiological processes and which can be measured by soft material probes. Polydimethylsiloxane (PDMS) is an important polymeric material widely used in bio-MEMS devices such as micropillar arrays for cellular mechanical force measurements. The accuracy of such a measurement relies on choosing an appropriate material constitutive model for converting the measured structural deformations into corresponding reaction forces. However, although PDMS is a well-known viscoelastic material, many researchers in the past have treated it as a linear elastic material and employed the simple cantilever beam equation to calculate the force from observed deflection, which could result in errors of cellular traction force interpretation. In this paper, the mechanical properties of PDMS were characterized by using uniaxial compression, dynamic mechanical analysis, and nanoindentation tests in both macro-and micro-scales, as well as finite element analysis. A generalized Maxwell model with the use of two exponential terms was used to emulate the mechanical behavior of PDMS at room temperature and the subsequent nanoindentation characterizations. After we found the viscoelastic constitutive law of PDMS, we used it to develop a more accurate model for converting deflection data to cellular traction forces. The results indicate that the linear cantilever beam model could significantly overestimate the cellular forces. Furthermore, in Situ cellular traction force evolutions of cardiac myocytes were demonstrated by using this new conversion model. The results presented by this paper are believed to be useful for biologists who are interpreting similar physiological processes.