近年來離子凝膠已被廣泛地應用於穿戴式電子裝置，特別是作為電容式感測器的主要材料。電容式感測器通常以具離子導電性的材料包裹介電層而組成的三明治結構為主。當壓力施加於感測器時，感測器的體積變化同時也會造成感測器的電容值改變，並可以此作為感測用的訊號。然而用傳統的模具做法很難製造出高敏感度的壓力感測器，而其他的先進製造方法，如:三維列印，提供了一個簡單的方法來製造穿戴式的感測器。其中數位光處理列印技術利用了局部光聚合來製作高解析度的複雜三維幾何結構，因此數位光處理列印技術很適合用來製作感測器。
在此工作中，我們使用可聚合深共熔溶劑作為數位光處理列印的樹脂墨水。深共溶劑已經被作為新型的溶劑被廣泛的它的應用領域，主要由氫鍵供體與氫鍵受體組成。由於其中強力的氫鍵作用力，深共熔溶劑的熔點比起原本的組成物理想熔點還要低上許多。我們選擇了氯化膽鹼、尿素和丙烯醯胺來作為可聚合的深共熔溶劑。與其它的深共熔溶劑相比，尿素提供的強氫鍵強作用力使得可以在不加入化學交聯劑的情況下以光聚合的方式製備出高強度的離子凝膠。此類材料亦呈現了自修復與快速回復等等特性。另外，離子凝膠的機械強度，可進一步使用可再生的奈米材料，纖維素奈米晶體，來進一步增強。我們後續利用了可見光引發的數位光處理列印與深共溶劑來製作電容式感測器。透過設計離子凝膠表面之微針結構，我們可大幅提升電容式感測器的敏感度。簡而言之，我們設計出了可3D列印的光固化墨水來製備穿戴式電子裝置所需要之高強度、可自修復與可快速回復的離子凝膠材料。

Ionogels have been widely investigated as wearable electronics, especially capacitive sensors that respond to pressure. Typical capacitive sensors are assembled by sandwiching a dielectric with two ionic conducting materials. The volumetric change of the sensors under pressure leads to the change of capacitance as the signals. However, traditional methods such as molding are difficult to prepare sensors with high sensitivity. Advanced manufacturing, such as 3D printing, may provide a simple strategy for constructing functional wearable sensors. In particular, digital light processing (DLP) uses the localized photopolymerization of resins to make geometrically complex 3D structures with high resolution. Therefore, DLP has enormous potential for the manufacturing of sensors.
In this work, we proposed a photo-resin composed of polymerizable deep eutectic solvents (DESs). DESs have been studied as renewable solvents for a wide range of applications. It is a combination of hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA). Because of the strong hydrogen bonding, the melting point of DESs becomes lower compared to the individual components. We chose choline chloride, urea, and acrylamide (AAm) to form a polymerizable DES for DLP printing capacitive sensor. Compared with other DESs, the urea-based DES provided strong hydrogen bonding for mechanically robust ionogels without chemical crosslinkers after photopolymerization. These ionogels exhibited self-healing capability and fast self-recovery. The stiffness of the ionogels could be further enhanced by adding renewable fillers such as cellulose nanocrystals (CNCs). Visible-light-induced DLP further led to the rapid fabrication of ionogels with complex structures. We demonstrated that the sensitivity of the capacitive sensors could be significantly enhanced by 3D printed microneedle arrays on the surface of the ionogels. In short, this work provided 3D printable ionogels with high toughness, excellent efficiency of self-healing, and fast self-recovery for wearable electronics.

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