Texas Tech University

Researcher Receives Grant to Study Needle-Free Injection Hydrodynamics

George Watson

August 24, 2016

Test tubes

The grant comes from Inovio Pharmaceuticals to study the various fluid dynamics of medications administered through needle-free devices.


One in five people avoid the doctor due to a fear of needles.

The human propensity to avoid a doctor's office over one of any number of fears is neither old nor uncommon.

One of the more popular reasons people avoid the doctor is a fear of needles. In fact, roughly one in five people, or 20 percent, either refuse or put off seeking medical attention due to needle phobia, which is a broad term covering six different types of fears, from a fear of sharp, pointed objects to a fear of vaccines and vaccinations.

That fear, plus the safety of doctors from accidental punctures from needles in the course of administering medication, has led to the push toward needle-free injections, which uses a device to deliver miniscule jet streams of medications at high rates of speed that puncture the skin. A Texas Tech University researcher has teamed up with a prominent pharmaceutical company to study the hydrodynamics of needle-free injectors to look both at their properties and ways to improve their effectiveness.

Jeremy Marston, a professor in the Department of Chemical Engineering in the Whitacre College of Engineering, received a $235,794 grant from Inovio Pharmaceuticals to study how needle-free injection devices work, how certain fluids work in those devices and what improvements can be made.

“Basically, we want to understand a little bit more about the actual mechanics of the jets,” Marston said. “What we've noticed is there is a little bit of a spread when it hits the skin, which is undesirable, so now we're trying to think about how to eliminate that and have a nice streamline jet going straight into the skin.”

Piercing without injecting

Jeremy Marston

Jeremy Marston

It's hard for the average person – though they may be one of the 20 percent happy to go needle-free – to visualize medication getting under the skin without the skin being punctured.

In fact, it's hard to see at all since the process happens so quickly and at such a miniscule scale. Marston said the normal needle-free injection stream is only about 100 microns in diameter, or about the thickness of a human hair. It also travels at about 200 meters, or 600 feet, per second.

Medication in a cartridge is loaded into a syringe-like device that is pressed against the skin and then activated using either compressed gas or a spring which applies pressure to the plunger, forcing it down and forcing the liquid out at very high speeds. Using this method, medication can be tailored for a specific area under the skin, and the diameter of the stream of medication determines its final deposition depth under the skin.

Marston's study, however, will deal more with the momentum needed to get the medication jet to puncture the skin, and then how fluids of various viscosity work both with the device he developed in his lab – which was part of a previous study he performed for Bioject Medical Technologies, purchased by Inovio in March – and with devices developed by Bioject and Inovio.

“They want to understand more about how the devices are working,” Marston said. “When Inovio purchased Bioject and all its assets a few months ago they found in their archives the work I'd done for them. They also wanted to know a little bit more about the fluid dynamics aspect of the devices. That's how the introduction began.”

Push toward needle-free

It's not just alleviating a patient's fear of needles that makes needle-free injections more desirable.

Marston said the World Health Organization (WHO) is making a concerted effort toward making the global medical community needle-free to reduce the risk of cross-contamination of doctors who are accidentally punctured by needles. There are instances, Marston said, where needles are very difficult to replace, particularly with the administration of large doses of medication. Needle-free injections are more useful with small doses, most frequently with the injection of insulin.


Technology similar to this may deliver an alternative to needle-injection.

Marston's study also could help improve injection of certain types of fluids. He said fluids with different properties are more difficult to inject with a needle and syringe. Plus, needle-free injection has been shown through clinical trials to have better release response times, allowing for a longer, more gradual release of the drug into the patient's body.

“So, actually, needle-free injection disperses better than regular injection when you just deposit a single blob through a needle and syringe,” Marston said. “It disperses better and is absorbed slightly more slowly, so it may be preferred by some patients.”

Using the technology in his laboratory at Texas Tech, Marston will test fluids of various viscosities to see which ones react better in a needle-free injector. Some will be low viscosity, like water, while others will be high viscosity, like glycerin or honey.

Marston will use a high-speed camera to view how the various fluids react when injected at high rates of speed, which ones penetrate the skin better and more completely and which ones disperse easily.

“There are a few components to study,” Marston said. “There are a couple of really specific applications the company has, so those will be dictated more by the company. On the other hand, we want to do quite a broad, fundamental study so we can look at how these things perform on a whole range of fluid properties.”

Marston's devices in his lab also could undergo some modifications. The laser he uses to create the small jet streams comes from a large, $20,000 device that is not indicative of the small, hand-held devices needed to go through clinical trials. He has some modifications in mind to scale down to the size of a hand-held device.

Marston will hire a post-doctoral research associate to conduct the research with the various needle-free injection models to determine their range of applicability, then will attempt to build mathematical models and run simulations to develop more predictive capabilities that will guide future development of needle-free injection devices.

“Hopefully it leads to an understanding and we start thinking about how to make these devices more efficient and possibly even more cost-effective as well.”

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