In this article, a low-cost, simple, and rapid fabrication of paper-based analytical devices (PADs) using a wax screen-printing method is reported here. The acid–base reaction is implemented in the simple PADs to demonstrate to students the chemistry concept of a limiting reagent. When a fixed concentration of base reacts with a gradually increasing concentration of acid, a dramatic demonstration allows students to discover the limiting reagent by naked eyes observing the color change from phenolphthalein as an indicator. This demonstration is not only a new approach to enhancing students’ learning of the chemistry concept of the limiting reagent, but also presents potential applications of PADs into all levels of chemistry from middle school through college classes.

中文翻译：

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制造简单的蜡丝网印刷纸质分析仪器，以证明在酸碱反应中限制试剂的概念

在本文中，本文报道了一种使用蜡丝网印刷方法的低成本，简单且快速的纸质分析设备（PAD）的制造方法。在简单的PAD中可以进行酸碱反应，以向学生展示限制剂的化学概念。当固定浓度的碱与逐渐增加的酸浓度发生反应时，生动的演示使学生可以肉眼观察酚酞作为指示剂的颜色变化，从而发现限制剂。该演示不仅是增强学生对限制性试剂化学概念的学习的一种新方法，而且还展示了从中学到大学课程，PAD在各种化学水平上的潜在应用。