IEEE Trans Biomed Eng. 2018 Dec;65(12):2808-2813. doi: 10.1109/TBME.2018.2818463. Epub 2018 Mar 22.
In this paper, we present a smart capsule that can release its payload after a predetermined/adjustable delay subsequent to passing from the stomach into the small intestine. The described capsule (9 mm × 22 mm) comprises a pH-sensitive hydrogel-based switch, an electronic compartment containing a capacitor charged to 2.7 V, and a drug reservoir capped by a taut fusible thread intertwined with a nichrome wire. The nichrome wire, capacitor, and pH-responsive electrical switch are connected in series. The pH transition the capsule encounters when it enters the small intestine triggers controlled swelling of the pH-responsive hydrogel, which pushes a conductive elastic membrane to close an electrical switch. This initiates a sequence of events, i.e., the discharge of the capacitor, heating the nichrome wire, breakage of the fusible thread, and release of the payload stored in the capsule reservoir through the unlatched cap. The time lag between initiation of hydrogel swelling (by the near-neutral pH of the small intestine) and payload release is controlled by the deflection of the conductive elastic membrane and the gap separating the contacts. The release time can be set to within ±5 min after one hour in the small intestine (start of the swelling) increasing to ±40 min after 4 h.
本文提出了一种智能胶囊，它可以在通过胃部进入小肠后，根据预设/可调节的延迟时间释放其有效载荷。所描述的胶囊（9mm×22mm）包括一个基于 pH 敏感水凝胶的开关、一个装有 2.7V 电容器的电子舱，以及一个由紧绷的易熔线和镍铬合金线交织而成的药物储存器的盖子。镍铬合金线、电容器和 pH 响应电开关串联连接。当胶囊进入小肠时遇到的 pH 转变会触发 pH 响应水凝胶的受控膨胀，从而推动导电弹性膜关闭电开关。这会引发一系列事件，即电容器放电、加热镍铬合金线、易熔线熔断以及通过未锁定的盖子释放储存在胶囊储存器中的有效载荷。水凝胶膨胀（由小肠的近中性 pH 引发）和有效载荷释放之间的时间延迟由导电弹性膜的挠度和触点之间的间隙控制。释放时间可以在进入小肠后的 1 小时内设置在±5 分钟内（开始膨胀），在 4 小时后增加到±40 分钟。
