基于电驱动液膜图形化及转移的有机薄膜纳米晶体管印刷制造新方法

Although organic thin-film transistor (OTFT) has many advantages such as solution-processibility, light-weight, the possibility of large-area processing, low cost, and high flexibility, it is difficult to fabricate the OTFT with high accuracy, high efficiency and low cost. In this project, we propose a novel technique for OTFT fabrication based on liquid film patterning and transferring driven by electric field. The technique makes use of the spontaneous wetting and dewetting of the liquid film on the patterned areas with surface energy differences, and it utilizes a template to induce the nano-patterning of the liquid film, whose surface wettability can be changed by the adjustable electric field added on the two electrodes of the the template. Then, the patterned liquid film will be transferred on the flexible substrate completely and with high accuracy through regulating the shape of the capillary bridge formed by the liquid film between the template and the flexible substrate. The fabrication of the OTFT can be devided into patterning and transferring process respectively. It includes pattering the first layer of the OTFT and then transferring the patterned layer to the flexible substrate. After the first layer on the flexible substrate has been solidified, the second layer of the OTFT will be patterned by its template and then transferred and solidified on the flexible substrate. By the above process, all the functional layers of the OTFT can be made.The proposed process has the similar process as the routine printing technique, but it has the ability to fabricate the features with the nano scale. The proposed technique bypasses the disadvantages of the routine methods such as the complicated and repeated process consisted of making mask layers firstly and then making the functional layers during the optical lithography and nano imprint lithography. Meanwhile, the traditional process must be assisted by the etching and lift-off steps repeatedly. The proposed method also avoids the common problems during the routine nano-fabrication process such as the vacuum environment, the pressure disturbance and contact contamination, and it solves the limitation of the low resolution in the traditional printing process. The research contents in this project include: the patterning characteristics due to the wetting and dewetting of the functional liquid film induced by the template driven under the electric field; the mechanism of the reversible conversion of the template wettability driven by the applied electric field; the controllable transferring behaviors of the patterned liquid film from the template to the flexible substrate, and the influences of the configuration and dimensions of function layers on OTFT performances. This project aims to develop an original nano printing method, which can fabricate the OTFT accurately, efficiently and cheaply.

针对有机薄膜纳米晶体管的高精度、高效率、低成本的规模化制造难题，本项目提出一种新的印刷制造方法，利用液态薄膜在表面能差异区域的自发润湿、去湿特性，通过电场驱动的润湿性调控模板诱导来实现OTFT功能薄膜的图形化成形；然后通过电场实时调控毛细桥的形态来实现模板上的图形化薄膜向柔性基底的完全、精确转移；OTFT各功能结构层的制造，可通过分层成形、逐层依次转移的方式来实现。该方法绕过了以光刻和压印工艺为代表的先掩膜层、后功能层的多次反复加工、同时需要刻蚀、剥离等多种工序配合的复杂工艺过程，也避开了真空环境、压力干扰、接触污染等问题，还解决了传统印刷技术分辨率低的缺陷。本项目将在电场驱动调控模板诱导下功能薄膜图形化润湿和去湿行为、电驱动下浸润性可逆转变机理、图形化液膜从模板向基底的可控转移机理、OTFT结构尺寸对其性能的影响规律等方面探索基础理论，解决其中涉及的关键技术难题，形成独立自主的知识产权。

本项目针对OTFT的功能和结构特点，提出了一种基于润湿性图形化及转移的OTFT制作方法。采用理论分析与试验研究结合的方法，通过大量的工艺试验，取得了丰富的试验数据，在基于电驱动润湿性转变的OTFT图形化成形和转移工艺的研究中取得了显著进展，具体包括：揭示了PDMS选择性粘附特性的机理和本质规律；阐明了电荷的运动行为影响表面润湿性变化的作用机制并进一步研究了电场驱动调控下表面润湿性发生超疏水/超亲水可逆转变的机理；研究了干扰分层转移过程中结构层对准精度的纳米粒子/聚合物复合材料热膨胀系数可调性的影响因素和控制规律。进行了超疏水/超亲水可逆转变的相关实验，提出并完善了功能层精确成形的调控方法；进行了复合模板的制备实验并完成了模板的结构优化，实现了对OTFT各功能结构层以及源极、栅极和漏极的图形化成形精确可控，并提高了分层转移过程中结构层的对准精度，开展了各功能层的转移实验并最终完成OTFT的制备和性能检测。本项目在电场驱动的润湿性转变及图形化成形机理方面探索了基础理论，为基于电驱动润湿性转变的OTFT功能结构层的可控成形和转移制作方法提供了理论依据。