This microneedle array has backward-facing barbs that interlock with tissue. (Credit: Riddish Morde)

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.

Microneedles (miniaturized needles) are gaining attention because they 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.

Using chicken muscle tissue as a model, the researchers showed that tissue adhesion with their microneedle is 18 times stronger than with a barbless microneedle. Their creation outperforms previously reported examples, resulting in more stable and robust drug delivery, collection of biofluids, and biosensing, the study says.

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