A Linear Permanent Magnet Synchronous Motor for Large Volume Needle-Free Jet Injection

Abstract

Needle-free jet injection allows delivery of liquid drugs through the skin in the form of a narrow fluid jet traveling at high speed, minimizing the risk of accidents. The use of a controllable actuator to drive this process has many advantages, but the voice coil actuators previously used are too large and heavy for practical use with common injection volumes (1 mL). We instead propose a compact slotless tubular linear permanent magnet synchronous motor design for jet injection. The design was determined by utilizing a semi-analytical electromagnetic modeling technique to predict the performance of any given motor design, an optimization scheme for the motor mass at a given power dissipation, and an automated routine for estimating cogging force using finite-element analysis. A prototype motor was constructed, with a nominal mass of 322 g, a stroke of 80 mm, and a target operating power of 1.2 kW; experimental data show that the motor constant is within 10% of the target, and that the cogging force is in close agreement with the model. Test ejection of water into a force sensor verified that the motor is fit for needle-free injection. The design methodology explained here shows the benefits to integrated design optimization of both the actuator and the load, particularly in systems that drive fluid pressure loads, and also opens the door to controllable injector designs for larger volumes.

Design and Analysis: Servo-Tube-Powered Liquid Jet Injector for Drug Delivery Applications

“…It should be noted that studies that examine this motor design have been conducted concurrently with the development of this prototype [50]. The studies conducted by Do et al [51,52] illustrate the optimization procedures for sizing a permanent magnet synchronous motor used for liquid jet delivery and test a custom-built motor in an open-loop configuration without current control. In this study, a prototype that utilizes a commercially available linear motor with well-established motor constants and parameters, as well as modern power electronics to provide true closed-loop control, is constructed.…”

Framework for efficient dynamic analysis applied to a tubular generator for suspension applications

“…Furthermore, the energy that is normally dissipated in passive suspension solutions can be partly recuperated by such electromechanical machines, making the latter particularly attractive from an efficiency point of view [5][6][7][8]. Finite element analysis (FEA) is a mandatory step to accurately model and design electromechanical devices [9][10][11]. Moreover, to fully analyze the energy harvesting capabilities of a vibration harvester utilized in vehicle suspensions, the corresponding finite element method (FEM) model should be assembled, solved, evaluated, and intensively iterated for different road conditions.…”

“…Finite element analysis (FEA) is a mandatory step to accurately model and design electromechanical devices [9][10][11]. Moreover, to fully analyze the energy harvesting capabilities of a vibration harvester utilized in vehicle suspensions, the corresponding finite element method (FEM) model should be assembled, solved, evaluated, and intensively iterated for different road conditions.…”

Application of Linear Permanent Magnet Flux-Switching Motors to Needle-free Jet Injection

“…Mechanically-powered jet injectors offer limited control over the injection depth and jet velocity, resulting in occasional bruising and other adverse effects [2]. Recently, high force density direct-drive linear motors [3], [4] have been used to enable electronically controlled injectors with superior repeatably and consistency. The voice coil motor (VCM) hand-piece in [5] has a total mass of 426 g, and requires peak electrical power of 5 kW to deliver a 300 µL drug volume.…”

“…The voice coil motor (VCM) hand-piece in [5] has a total mass of 426 g, and requires peak electrical power of 5 kW to deliver a 300 µL drug volume. A higher-performance injector based on the tubular permanent magnet linear synchronous motor (PMLSM) assembly in [4] requires 1.4kW to deliver as much as 1 mL of drug, weighs 322 g for just the coil and magnets, and 600 g in total when adding support components. Even with such progress, this synchronous permanent magnet motor is still larger and heavier than the form factor preferred for a handheld medical device.…”