A Magnetically Actuated Drug Delivery System for Robotic Endoscopic Capsules

Abstract

There is an increasing need to incorporate an actively controlled drug delivery system (DDS) into the next generation of capsule endoscopy in order to treat diseases in the gastrointestinal tract in a noninvasive way. Despite a number of attempts to magnetically actuate drug delivery mechanisms embedded in endoscopic capsules, longer operating distances and further miniaturization of on-board components are still drawbacks of such systems. In this paper, we propose an innovative magnetic system that consists of an array of magnets, which activates a DDS, based on an overly miniaturized slider-crank mechanism. We use analytical models to compare the magnetic fields generated by cylindrical and arc-shaped magnets. Our experimental results, which are in agreement with the analytical results, show that an optimally configured array of the magnets enhances the magnetic field and also the driving magnetic torque and subsequently, it imposes a high enough force on the piston of the DDS to expel a required dose of a drug out of a reservoir. We conclude that the proposed magnetic field optimization method is effective in establishing an active DDS that is designed to deliver drug profiles with accurate control of the release rate, release amount, and number of doses. There is an increasing need to incorporate an actively controlled drug delivery system (DDS) into the next generation of capsule endoscopy in order to treat diseases in the gastrointestinal tract in a noninvasive way. Despite a number of attempts to magnetically actuate drug delivery mechanisms embedded in endoscopic capsules, longer operating distances and further miniaturization of on-board components are still drawbacks of such systems. In this paper, we propose an innovative magnetic system that consists of an array of magnets, which activates a DDS, based on an overly miniaturized slider-crank mechanism. We use analytical models to compare the magnetic fields generated by cylindrical and arc-shaped magnets. Our experimental results, which are in agreement with the analytical results, show that an optimally configured array of the magnets enhances the magnetic field and also the driving magnetic torque and subsequently, it imposes a high enough force on the piston of the DDS to expel a required dose of a drug out of a reservoir. We conclude that the proposed magnetic field optimization method is effective in establishing an active DDS that is designed to deliver drug profiles with accurate control of the release rate, release amount, and number of doses.

Analysis of the magnetic torque on a tilted permanent magnet for drug delivery in capsule robots

“…Since the drug release mechanism is actuated by a magnetic torque, the operating distance r 1 can be increased to meet the requirements of a more realistic medical application (i.e., r 1 >120 mm) while the dimensions of the external magnetic system are scaled up at the same time [13,17]. A magnetic torque τ z′ , as shown in Fig.…”

“…Within the capsule robot, we define a coordinate system X′Y′Z′, the origin of which coincides with the IPM's centre. When the IPM's centre coincides with the centre of ASMs and the axes of the two coordinate systems are aligned, it is possible to approximately transmit a magnetic peak torque τ z′ of 3.5 [mNm] on a 3.1 mm cubic IPM by using only 4 ASMs that generate approximately 114 [mT] at the IPM's centre [17]. However, in a real application, the IPM can be off the centre and/or tilted as it will move along with the capsule robot.…”

Size Optimization of a Magnetic System for Drug Delivery With Capsule Robots

“…However, two additional facts should be considered when this magnetic system is scaled up [16]: 1) 5 [mNm] is more than enough peak torque to actuate the piston of the drug release module, knowing that 3.5 [mNm] is sufficient for the release, 2) a peak torque is not always required to actuate the piston. For instance, magnetic torques of 2 and 4 [mNm], which can be obtained when ∅ =30 0 and ∅ =60 0 , respectively, are also adequate to release a variety of drug compounds.…”

“…In a real application, the IPM can be off the centre and tilted as it will move along with the CE. However, for the sake of simplicity, the optimization of the driving magnetic system is carried out by assuming that it can only rotate about the z axis and that the IPM is concentric with the driving magnetic system [16]. The IPM's centre is also located at point P and can freely rotate about the z axis.…”

“…Specifically, we focus on the size optimization of a driving magnetic system which consists of an array of arcshaped permanent magnets (ASMs) that we have proposed to release drug in WCE [16]. This driving magnetic system generates a rotating magnetic field that imparts a magnetic torque to a small IPM that is placed in a prototype of CE and actuates a slider-crank mechanism to release drug.…”