| AVS 63rd International Symposium & Exhibition | |
| MEMS and NEMS | Thursday Sessions |
| Session MN+BI-ThM |
| Session: | ‘Fantastic Voyage’ – the New Micro/Nano/Bio Systems Frontiers |
| Presenter: | Babak Ziaie, Purdue University |
| Authors: | W. Yu, Purdue University R. Rahimi, Purdue University M. Ochoa, Purdue University B. Ziaie, Purdue University |
| Correspondent: | Click to Email |
This paper reports on a magnetic-proximity-fuse method for site-specific drug release in the gut. As an embodiment, a capsule is comprised of two compartments; one houses a charged capacitor and a reed switch (magnetic switch) while the other accommodates the drug reservoir, whose lid is latched by a taut nylon thread intertwined with a NiCr wire. Meanwhile, the wire is connected to the capacitor via the switch. Once within the proximity of a magnet, the switch closes and the capacitor discharges on the wire, melting the fusible thread and opening the reservoir.
Pharmaceutical companies have been interested in releasing medications at specific sites in the gut. Many drug absorption studies (DASs) use Enterion [1] capsule which incorporates a loaded spring that is RF-actuated, pushes a piston and forces the drug out through a hole. The capsule location is monitored via γ-ray scintillating-imaging. Other similar devices include InteliSite [2] (tracked by x-ray) and IntelliCap (tracked by pH). Though suitable for DASs in clinical settings, these approaches are not practical for use in larger populations. This is mainly due to the problems related to the need for real-time localizing the capsule. Thus, we present an alternative approach using a Smart Capsule incorporating a magnetic-proximity fuse.
Fig. 1 depicts a capsule traveling through the gut in proximity to a magnet. The capsule consists of two chambers. The right one contains a capacitor (1F, 2.7V) and a reed switch. The capacitor is charged before use. A NiCr wire is connected to the capacitor and the switch, with two ends in the right chamber and the rest intertwined with a nylon fuse in the drug reservoir. Along the axis is a rubber band linking the fuse to a cap, covering the reservoir with an elastic layer for reliable sealing. Additionally, an elastic rod is used as a loaded spring pushing the cap out once the fuse breaks. As in Fig. 2, the band holds the cap initially. When the capsule meets a magnetic field to close the switch, the NiCr wire is heated, melting the fuse (60~85ºC) and opening the cap. Fig. 3 shows a photo of a Smart Capsule (9mm×26mm).
Fig. 4 shows snapshots of the capsule traveling in a tubing at various points with respect to the magnetic marker. The capsule starts to open in frame “a” (1sec) at a separation distance of 1mm from the magnet, with the opening completed (cap totally separated from the capsule) in frame “e” (17sec). Considerable diffusion and mixing of the powdered dye in water is observed within a minute, frame “f”. Fig. 5 shows the relationship between the capacitance and the charging voltage necessary for melting the fuse through a NiCr wire (~0.23ohms).