Air-Powered Liquid Needle Free Injectors: Design, Modeling and Experimental Validation

Liquid needle free injectors are biomedical devices that deliver medication via the creation of high speed liquid jets without the use of hypodermic needles, have been a topic of interest in the scientific community for quite some time. This study focuses on the development and analysis of liquid jet injectors powered by air. Studies demonstrate that the majority of commercially available injectors are gas/air powered units; however there is no indication of a model that prescribes the performance characteristics of this particular type of injector. Consequently the main goal of this research is to develop and validate a model capable of predicting the behaviour of such devices. In this study, the development and analysis of a model for air-powered injectors is accomplished first by constructing a prototype injector that functions in a very similar fashion and produces jets of similar geometry and velocities as the vast majority of commercially available units. Furthermore, the injector is designed in such a way that the parameters such as, driver pressure, injection chamber length and volume as well as nozzle geometry can be varied. An initial evaluation of the prototype injector is performed to ensure it can be used to accurately conduct testing. The prototype injector is then used to validate a fluid mechanics model constructed based on previous work from Baker and Sanders [IEEE Trans. Biomed. Eng. 46:235-242, 1999]. Experiments that map stagnation pressures of the jet through the use of a piezoelectric force transducer are performed in order to validate the performance of the model. These experiments describe the peak and average stagnation pressures of the jet based on the effect of different parameters such as driver pressure (400-800 kPa), nozzle size (130-250 μm) and injection chamber length (10-25 mm). The results of these tests are then compared to the behaviour prescribed by the model. An analysis of these results indicates that the present model can accurately be used to predict the performance of air-powered needle free liquid jet injectors

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

The current state of commercially available needle-free liquid jet injectors for drug delivery offers no way of controlling the output pressure of the device in real time, as the driving mechanism for these injectors provides a fixed delivery pressure profile. In order to improve the delivery efficiency as well as the precision of the targeted tissue depth, it is necessary to develop a power source that can accurately control the plunger velocity. The duration of a liquid jet injection can vary from 10 to 100 ms, and it generate acceleration greater than 2 g (where g is the gravity); thus, a platform for real-time control must exhibit a response time greater than 1 kHz and good accuracy. Improving the pioneering work by Taberner and others whereby a Lorentz force actuator based upon a voice coil is designed, this study presents a prototype injector system with greater controllability based on the use of a fully closed-loop control system and a classical three-phase linear motor consisting of three fixed coils and multiple permanent magnets. Apart from being capable of generating jets with a required stagnation pressure of 15–16 MPa for skin penetration and liquid injection, as well as reproducing typical injection dynamics using commercially available injectors, the novelty of this proposed platform is that it is proven to be capable of shaping the real-time jet injection pressure profile, including pulsed injection, so that it can later be tailored for more efficient drug delivery

On the application of gas detonation-driven water jet for material surface treatment process

The recent advances in pulsed waterjet technology create new opportunities for developing green manufacturing process. New methods of generating pulsed water jets in a simple, controlled fashion are sought after to improve the efficiency of current techniques. This paper examines an unconventional concept for producing high-speed liquid jets, created by detonation phenomenon. The technique relies on harnessing the pressure gain from a detonative combustion to drive a piston that in turn propels a liquid jet at high speed. The proof-of-concept, together with recent pulsed detonation engine development, holds promising potential for detonation-driven pulsed water jet generation applied to manufacturing process

Controlled release using gas detonation in needle-free liquid jet injections for drug delivery

The advent of new drug therapies has resulted in a need for drug delivery that can deal with increased drug concentration and viscosities. Needle-free liquid jet injection has shown great potential as a platform for administering some of these revolutionary therapies. This investigation explores the detonative combustion phenomenon in gases as a simple and efficient means of powering needle-free liquid jet injection systems. A preliminary, large-scale prototype injector was designed and developed. In contrast with the widely used air-powered and electrical driven needle-free injectors, the proposed detonation-driven mechanism provides equivalent liquid jet evolution and performance but can efficiently provide a controllable power source an order magnitude higher in strength by varying combustible mixtures and initial conditions. The simplicity and power output associated with this concept aid in improving current needle-free liquid injector design, especially for delivery of high volume, high viscosity drugs, including monoclonal antibodies, which target precise locations in skin tissue

Early hip fracture surgery and rehabilitation. How to improve functional quality outcomes. A retrospective study

Introduction: Hip fractures are one of the major disability causes associated with a high morbidity and mortality rate. Early surgery and stable fixation could be associated with better pain control, possibly lower mortality rates, and early recovery of autonomy. Aim: The aim of this study was to analyze a population affected by hip fractures exploring the effects of an early surgery and rehabilitation approach in relation to functional outcomes. Materials and methods: This study included 140 adult patients (mean age 79.35±11.71, range 66-94 years) with hip fractures admitted to the orthopedic unit of the University Hospital of Messina who underwent surgery and a rehabilitation program while hospitalized. Exclusion criteria were patients not surgically treated or discharged with no rehabilitation sessions. Clinical outcomes were evaluated post-surgery and before discharge as follows: pain quantification using the visual analogue scale and functional evaluation using the Barthel Index. A rehabilitation protocol was started within 48 hours after surgery. Results: The study sample resulted in 140 patients. Eighty-seven of them (63.14%) underwent hip replacement surgery, and 53 patients (37.86%) underwent internal fixation surgery. The greater part of the sample (68.42%) had surgery within 48 hours. Patients with more comorbidities had worse clinical outcomes, as shown by the Barthel Index, timing of verticalization and walking, and pain control. Between admission and discharge, the Barthel Index score improved, as did the pain complained of by most patients. Conclusions: A direct connection between orthopedics and the rehabilitation team, even after discharge, should be established and promptly organized to gain the best clinical outcomes. Indeed, we propose the triad early verticalization, pain control, and Barthel Index as a possible tool to define functional quality outcomes in post hip fracture surgery

Liquid Needle Free Injectors: Design and Analysis of Power Sources

Drug delivery without the use of hypodermic needles has been a long-term objective within the medical field. Although there exist many different needle free technologies, these have typically been limited to the delivery of micro-molecules and small volumes. This dissertation focuses on liquid jet injection, a technique utilizing micro size, high-speed liquid jets for the delivery of macro-molecules in line with commercially developed injectables. The devices using this technique are known as needle-free liquid jet injectors (NFJI). However, pain, bruising, hematomas, incomplete delivery, and cross-contamination, have limited their widespread clinical use. This dissertation will focus on contributing to the development of the most important aspect of an NFJI, the power source. Power source requirements of NFJIs are established through a numerical study utilizing a computational fluid dynamic model constructed by Nakayama et al. (2013) and subsequently analyzing the effect of drug viscosity to underline the requirements for successful liquid jet injection. The results of this study highlight that increasing viscosity to levels required by novel drug therapies will make it difficult for commercially available NFJI to deliver viscous injectables. These limitations are addressed by the analysis of a servo-tube actuated NFJI, this prototype advanced the work conducted by Taberner et al., (2012) and Do et al., (2017), by utilizing advanced power electronics and fully closed-loop control to illustrate the viability and real-time controllability of linear PMSMs for powering NFJIs. This yielded a prototype device producing accurate pressure profiles and large delivery volumes, however demonstrated slight difficulties in scalability. In response, a combustion-driven injector was analyzed to provide rapid energy release in a smaller form factor. The study yielded a prototype capable of producing jets attaining stagnation pressures above 80 MPa, by detonating a gaseous mixture of acetylene-oxygen. A model that characterizes the pressure output of the device is also developed and verified experimentally. A novel NFJI, that combines the scalability and energy release of the combustion-driven injector, with the controllability of a servo tube-powered NFJI is also presented. This concept utilizes a rotary servo motor, electromagnetic clutch and drive screw, to reduce the power requirements at the onset of liquid jet injection while providing real-time control of jet stagnation pressure