Will inkjet technology replace hypodermic needles?

What child doesn't experience fear and anxiety over the prospect of getting a shot at the doctor's office? Even for many adults, the experience of getting an injection isn't pleasant. Wouldn't it be nice if the nurse could forgo that needle-tipped syringe?

Or, think how convenient it would be for people who must manage complicated dosage schedules of medications to wear a specialized drug patch instead, which could automatically control the delivery of different drugs throughout the day.

Scenarios like these might soon become reality, thanks to a new device developed by Hewlett-Packard (HP). The device can be thought of as a computer-controlled drug patch -- similar to the look and feel of a nicotine patch (although this one is a little heavier). The patch can painlessly inject precise amounts of drugs into the body. The patch is based partly on HP's existing inkjet technology and partly on an emerging technology involving microneedles. The inkjet system controls the flow of drugs through the patch, and the microneedles, made of materials like silicon, metals, and biodegradable polymers, help transmit the drugs through the skin [source: Toon].

These polymer microneedles stand approximately 1 millimeter tall.
Photo courtesy Gary Meek/ Georgia Institute of Technology

To understand the patch, let's first look at how microneedle technology works. Microneedle devices usually consist of hundreds or even thousands of tiny microscale needles, evenly spaced into an orderly array of rows and columns. (Imagine a bed of nails, only on a much smaller scale and far less scary.) Each microneedle is thinner than the diameter of a human hair and less than 0.1 millimeters in length -- just long enough to break through the outer layer of your skin. One microneedle alone could deliver only a small dosage of medication, but the whole array of microneedles could dispense a considerable amount.

So how are microneedle arrays able to inject drugs without causing pain? The answer lies in the length of each microneedle. Because each microneedle is so short, it penetrates through the outermost layer of your skin, called the stratum corneum, but doesn't reach your skin's pain receptors (located slightly deeper). Even if the microneedles do reach the pain receptors, the spacing and size of the needles prevents them from triggering pain signals. Their size also causes far less tissue damage than does a standard hypodermic needle.

Microneedles are a great way to get drugs into the body, but what does this have to do with inkjet technology? Keep reading to find out if a computer printer will administer your next flu shot.

Inkjet Drug Delivery

The inkjet portion of the drug-delivery patch precisely controls the flow of drugs through the microneedles -- in a way similar to how an inkjet printer head controls the flow of ink through its nozzles. In a thermal inkjet printer, each nozzle has its own reservoir of ink and also contains a resistive heating element. When a microprocessor sends electricity to each heating element, the ink around the element rapidly heats up and expands, expelling the specified amount of ink out of the nozzle. In the inkjet drug patch, a similar process is used to control the flow of drugs precisely through the tip of each microneedle and into the body.

And just as color printers can control the flow of more than one color of ink, inkjet drug delivery systems can be made to store and deliver many different drugs at once.

There are many advantages to using inkjet-technology dosage control. For example, it's important for drugs to be delivered in precise amounts. The microprocessor-controlled inkjet system is not only able to deliver exact dosages; it can automatically control a complex dosage schedule of multiple drugs. This capability could be especially valuable for children or for elderly patients who might have a hard time keeping track of their many scheduled medications. There's a wide range of other useful tasks that the device could potentially perform as well. For example, the microprocessor could be programmed to deliver drugs in response to a patient's vital signs, like blood pressure or body temperature [source: Kanellos].

microneedles on an applicator — An array of microneedles mounted atop an applicator.
Photo courtesy Harvinder Gill/Georgia Institute of Technology

While the inkjet drug delivery system is a breakthrough technology and has shown promising test results, it still has a long way to go before it can be used commercially. Just like all medical devices, it must be proven safe and effective by a series of tests overseen by the Food and Drug Administration. Another critical factor affecting the adoption of the device will be its cost. The electronic and microscale components of the inkjet system will likely be expensive to manufacture, although costs should go down with time.

So will inkjet technology replace hypodermic needles? The future is still unclear, but it looks like the answer might be yes for some applications. For example, in situations where automatic or precise dosages are important, like insulin for diabetic patients, the additional price of the inkjet technology might be tolerable. In other situations, microneedle array systems without the inkjet control might be a less costly alternative to conventional syringes.

Either way, it appears that the hypodermic needle's reign of terror is about to be challenged in a big way by micro-sized competition.

Will inkjet technology replace hypodermic needles?

Inkjet Drug Delivery

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