Inkjet microneedles


Trypanophobia, otherwise known as a fear of injections or hypodermic needles, is a condition that affects an estimated 10% of the population of America. It’s no secret medical injections have never been very popular amongst children and adults alike. Fortunately, a new technology is being developed for the controlled delivery of medicinal drugs, catering for complex schedules and dosages – all without the potentially daunting need for a hypodermic needle.  This revolutionary device comes with an appearance similar to a traditional nicotine patch (although heavier). The device uses inkjet technology to inject substances into the human body through a bed of microneedles with computer controlled precision. The inkjet system is used to control the flow of drugs and can be programmed to execute specific tasks, such as delivering doses over an extended period of time or in response to a patient’s vital signs.

This technology could utilise hundreds or even thousands of microneedles, each one thinner than the diameter of a human hair. An entire array of microneedles would be able to dispense a substantial amount of fluid. Part of the lure of this technology is that it would be completely painless. The microneedle is very short (less than 0.1 millimeters) so would penetrate the skins outer layer but would not reach the more deeply located pain receptors. A clinical study was performed in which 12 subjects all reported that the sensation of being injected by microneedles was similar to pressing their skin against a hard surface – significantly more subtle than a hypodermic needle injection.

Thermal inkjet technology is utilised to control drug dispensation through the microneedles. In a thermal inkjet printer, an electric pulse is transmitted through a heater, causing a rise in temperature making a bubble to form in the chamber and a large pressure increase which propels a droplet of ink out of the print head. This process is used to dispense fluids out of the microneedles and into the human body. The microprocessor controlled inkjet system is able to store and deliver a multitude of drugs in the same way an inkjet printer stores and delivers a multitude of colours. The inkjet microprocessor automatically controls complex drug dispension schedules, which can be particularly useful to the elderly or young who may have difficulties in managing schedules themselves.

Many safety risks associated with hypodermic needles are conveniently avoided with the inkjet drug delivery system, specifically the breaking of needles and air pockets in the syringe. Tissue damage is also dramatically reduced. This technology would bring a significant increase to the quality of life of diabetics, who have to inject themselves daily. Diabetics also benefit from the patch’s ability to dispense multiple drugs when desired. The ability to dispense both insulin and glucagon (which negates insulin’s effects) massively diminishes the risk of insulin overdose which looms during traditional injections.

While this technology is clearly revolutionary, certain factors need to be addressed before it hits the market. One particular concern is the potential risk of increased infection. The stratum corneum (outer-most layer of the epidermis) consists of dead cells and is designed specifically to protect underlying cells from infection and other dangers. A series of tests would need to be carried out by the Food and Drug Administration in order to certify that making such tiny holes in the skin does not allow bacteria and viruses into the human body. There is also the issue of price; this system is likely to be more expensive than traditional technology, especially initially. For applications such as the treatment of diabetics, the extra expenditure may be worthwhile, but this may not be the case for less critical applications. Either way, the hypodermic needle’s position as the foremost method of rapid liquid introduction into the body is about to be challenged in a major way.

Tim Phillips, Catenary Solutions

Further Reading

Technology Review

The Engineer

Science Daily