Actively Triggerable Metals via Liquid Metal Embrittlement for Biomedical Applications

Abstract

Actively triggerable materials, which break down upon introduction of an exogenous stimulus, enable precise control over the lifetime of biomedical technologies, as well as adaptation to unforeseen circumstances, such as changes to an established treatment plan. Yet, most actively triggerable materials are low‐strength polymers and hydrogels with limited long‐term durability. By contrast, metals possess advantageous functional properties, including high mechanical strength and conductivity, that are desirable across several applications within biomedicine. To realize actively triggerable metals, a mechanism called liquid metal embrittlement is leveraged, in which certain liquid metals penetrate the grain boundaries of certain solid metals and cause them to dramatically weaken or disintegrate. In this work, it is demonstrated that eutectic gallium indium (EGaIn), a biocompatible alloy of gallium, can be formulated to reproducibly trigger the breakdown of aluminum within different physiologically relevant environments. The breakdown behavior of aluminum after triggering can further be readily controlled by manipulating its grain structure. Finally, three possible use cases of biomedical devices constructed from actively triggerable metals are demonstrated.

3D Printing of Liquid Metals: Recent Advancements and Challenges

“…It is difficult to simultaneously balance the printing speed/ throughput and printing resolution of 3D printing, which hinders the widespread application of 3D printing. [174][175][176] To transform the high-throughput production of 3D printing into further mass production, it is essential to improve printing speed without sacrificing printing resolution. For example, Saha et al [177] introduced the face projection strategy of digital light processing to two-photon/multiphoton polymerization (TPP).…”

Functional heterophasic liquid metals

“…The solid metals in the LMs (that forms heterophasic LMs in this review) not only address the above challenges but also bring new features into the heterophasic LMs [26–28] . We list several examples: Adding metal elements to LMs can endow the resulting heterophasic LMs with distinctive functionality such as magnetic responsiveness from LM‐Fe/Gd/Ni, [29–31] superior catalytic activity from LM‐Pt/Pd/Rh, [32–34] and biomedical function from LM‐Cu/Zn/Mg, [35,36] (Figure 1a, colors represent the functionalities) [43,44] The properties of heterophasic LMs (e.g., morphology, strength, rheology, electrical/thermal conductivity, and chemical reactivity) can be tuned through compositions and are highly dynamic [38,45] in response to stimuli such as magnetic field and temperature [46] …”

“…Adding metal elements to LMs can endow the resulting heterophasic LMs with distinctive functionality such as magnetic responsiveness from LM‐Fe/Gd/Ni, [29–31] superior catalytic activity from LM‐Pt/Pd/Rh, [32–34] and biomedical function from LM‐Cu/Zn/Mg, [35,36] (Figure 1a, colors represent the functionalities) [43,44] …”

Liquid metal integrated PU/CNT fibrous membrane for human health monitoring

“…Gallium-based liquid metals (LMs) are metal alloys with a low melting point and high conductivity ( σ = 3.4 × 10 4 S/cm); good fluidity (viscosity ≈2 MPaS); and high deformability ( Zheng et al, 2019 ; Hang et al, 2021 ; Zhang et al, 2022 ). At present, LM has shown great utility value in soft robots ( Wang et al, 2018 ; Zheng et al, 2022 ), biomedicine ( Feig et al, 2022 ; Gao et al, 2022 ), energy management ( Zuraiqi et al, 2020 ; Zhang et al, 2021 ), flexible electronics ( Liang et al, 2022 ), etc. Besides, LM is suitable for manufacturing stretchable conductors because it can easily deform with the stretching and bending of flexible substrates ( Wang et al, 2023 ).…”