Karen-Christian Agno1,Keungmo Yang1,Sang-Hyuk Byun1,Subin Oh1,Simok Lee1,Heesoo Kim1,Kyurae Kim1,Sungwoo Cho1,Won-Il Jeong1,Jae-Woong Jeong1
Korea Advanced Institute of Science and Technology1
Karen-Christian Agno1,Keungmo Yang1,Sang-Hyuk Byun1,Subin Oh1,Simok Lee1,Heesoo Kim1,Kyurae Kim1,Sungwoo Cho1,Won-Il Jeong1,Jae-Woong Jeong1
Korea Advanced Institute of Science and Technology1
Conventional intravenous needles are manufactured from materials with high and fixed stiffness that allows for rigid tissue insertion followed by therapeutic fluid delivery into the bloodstream. Their rigid structure not only causes chronic tissue complications among hospitalized patients receiving IV medication but also heightens the risk of needle stick injuries among healthcare providers after usage. Here, we introduce a liquid metal-based needle that can autonomously change its stiffness by body temperature (~ 37 °C) to match the softness of the delicate blood vessel after rigid tissue insertion. The needle has a rectangular hollow structure formed from U-shaped liquid metal frames which are encapsulated with silicone of high tear strength. We utilize gallium for the channel frames because of its unique phase conversion between solid (elastic modulus = 9.8 GPa) and liquid, low melting temperature (<i>T<sub>melt</sub></i> = 29.76 °C) below the body temperature, and biocompatibility. At room temperature (20-25 °C), the needle is rigid and straight like the commercial rigid needle, but it becomes soft and compliant after rigid tissue insertion (~ 37 °C) within 60 seconds as the encapsulated gallium frames melt, achieving three orders of magnitude of independent modulus-tuning ratio. After one usage, the softened needle becomes completely non-reusable because supercooling phenomena prevent solidification of liquified gallium. Our <i>in vivo</i> studies indicate that the softening needle has potential to reduce inflammation injury in the injection site owing to its enhanced tissue-adaptability in comparison to commercial rigid IV access device of comparable size. To further add functionality, a nanomembrane temperature sensor was integrated with the softening needle, demonstrating that the integrated system-device can monitor the on-site temperature to measure core body temperature or undesirable fluid leakage during IV administration. Overall, the gallium-based intravenous needle envisions wide-range of clinical applications, as it actively responds to the call of the World Health Organization for the improvement of patient care and safer medical practice.