Transformative IV needle: A needle that softens via body temperature

Can you imagine a needle that softens during indwelling use, can freely deform and adapt to the movement of tissues, and stays soft after injection?
Published in Biomedical Research
Transformative IV needle: A needle that softens via body temperature

We had developed an intravenous (IV) needle that can independently and fully adapt to tissues upon insertion via body temperature. We call this device as “transformative IV needle”, primarily because the needle is capable of varying its own hardness – to the level similar to the softness of the biological tissue.

Commercial medical needles and catheters: Current challenges and solutions

Commercial IV needles and catheters are traditionally manufactured using stainless steel metal and plastic which do not match the mechanical property of the soft tissues. Such mechanical mismatch between the interface of the rigid IV needles and catheters and the soft tissue can cause various concerns in the hospital settings.

Do you know that IVs fail about 46% of the time in major clinics even before IVs reach the end of the intended usage? The primary cause for such failure is the movement of a rigid IV access device with respect to the soft-walled vein1. Moreover, healthcare providers who handle needle injection have high chance of getting deadly viruses such as HIV, hepatitis viruses B and C, after post-needle injection, particularly with IV needles because of its direct contact with blood among other types of medical needles.

In 2015, the World Health Organization (WHO) launched a policy on safe injection practices that encourage the use of “smart” syringes that have features to prevent re-use, after a tremendous increase in the number of deadly infectious disease worldwide due to medical-sharp-related reuse. As a response, manufacturers of needle-syringe system develop built-in safety mechanism in the needle that safeguards the sharp tip of the assisted stainless steel needle after use to protect healthcare providers from needle stick injuries and prevent reusing of needles.

Despite such modifications, the existing materials used in manufacturing the commercial IV needles and catheters are highly inflexible which still leads to the pressing concern of large mechanical mismatch between the thin-walled vein and contemporary IV needles and catheters.

Softening IV needle: A promising innovation

The new transformative IV needle is made up of liquid metal gallium that forms the hollow, mechanical needle frame which is encapsulated within an ultra-soft polymer. We used gallium metal because of its solid-to-liquid phase transition property and low melting point (29.76 °C). At room temperature, gallium has sufficient hardness that enables puncturing of soft biological tissues. When exposed to body temperature, gallium melts. With these characteristics of gallium and using an ultra-soft polymer as an encapsulant, we were able to develop this softening IV needle. 

Figure 1. The transformative IV needle: A photo showing the needle becomes soft by body temperature that can adapt to soft tissue, and can still deliver fluid. After use, the IV needle remains completely soft, making the needle non-reusable that reduces the risk of accidental needle stick injury among patients and healthcare providers. 

Through series of systematic experiments, we showed that the needle is rigid enough to puncture the tissue having sufficient hardness that is comparable to the commercial 18G over-the-needle IV catheter. The same needle then irreversibly softens after insertion within 60 seconds under simulated body temperature, creating an intimate interface with respect to the thin-walled vein and reducing potential needle stick injury upon needle removal. After use, the needle will achieve a tissue-like softness that prevents needle reuse owing to the supercooling phenomenon, a state in which gallium melt remains entirely liquid below its melting temperature without becoming solid. Furthermore, our transformative IV needle has a maximum achievable flow rate that is equivalent to a commercial 22G IV catheter, and is capable of reliably delivering fluid. These findings indicate that the new IV needle can eliminate the risk of mechanical damage on the soft vein during indwelling use, and restricts the attempt to use the same needle again.

Biocompatibility studies play a crucial factor in the development of new IV needles since these IV needles will come in contact with blood. Our 14-day in vivo animal experiment using mice model indicated that the implanted softening IV needles caused significantly less inflammation in comparison to the commercial IV needles and catheters of similar sizes. The achieved softness of the transformative IV needle during indwelling use can increase the mobility among hospitalized patients receiving continuous IV medication, and reduce their discomfort caused by re-siting of rigid IV catheters every 72 to 96 hours. In addition, through liver perfusion model in mouse, we showed that our transformative IV needle has biocompatible fluid delivery compared to the standard IV catheter. Overall, these results indicate that the new IV needle has potential to reduce tissue injury through its achieved intimate tissue interfacing at soft state compared to rigid commercial IV needles and catheters of comparable size. 

Lastly, we also showed the potential of a customized ultra-thin temperature sensor integrated with the softening IV needle to measure on-site body temperature that can further enhance patient care. In mice model, we demonstrated the ability to monitor the core body temperature. In our ex vivo porcine muscle tissue model, we showcased the capability of detecting fluid leakage on-site, during IV administration.

Overall, we believe that the transformative IV needle can be a promising solution to the prevailing unethical needle reuse, while enhancing patient care during IV administration.


1 Helm, R.E., et al., Accepted but Unacceptable: Peripheral IV Catheter Failure. Journal of Infusion Nursing. 2015; 38(3):189-203.

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