Painful hypodermic needles may not be needed in the future to give shots, inject drugs, and get blood samples. With 4D printing, engineers have created tiny needles that mimic parasites that attach to skin and could replace hypodermic needles.
While 3D printing builds objects layer by layer, 4D goes further with smart materials that are programmed to change shape after printing. Time is the fourth dimension that allows materials to morph into new shapes. The 4D-print-ed microneedle array will allow for more robust and sustained use of minimally invasive, pain-free, and easy-to-use micro-needles for delivering drugs, healing wounds, biosensing, and other soft tissue applications.
Hypodermic needles are widely used in hospitals and labs to extract blood and inject drugs, causing pain, scarring skin, and posing an infection risk. People with diabetes often take blood samples multiple times a day with needles to monitor blood sugar levels.
Microneedles (miniaturized needles) are short, thin, and minimally invasive; reduce pain and the risk of infection; and are easy to use. But their weak adhesion to tissues is a major challenge for controlled drug delivery over the long run or for biosensing, which involves using a device to detect DNA, enzymes, antibodies, and other health indicators.
In nature, some insects and other organisms have developed microscopic features that adhere to tissue such as the microhooks of parasites, barbed stingers of honeybees, and scaled quills of porcupines. Inspired by these examples, the engineers developed a microneedle that interlocks with tissue when inserted, enhancing adhesion. They combined a micro 3D printing technique and a 4D printing approach to create backward-facing barbs on a microneedle.
The researchers showed that tissue adhesion with the microneedle is 18 times stronger than with a barbless microneedle, resulting in more stable and robust drug delivery, collection of biofluids, and biosensing.