Liquid Metal Biomaterials

This chapter introduces a new biomedical category of the liquid metal biomaterials which consists of the core theme of the present book. The major advancements as made before will be briefly summarized and future directions worth of pursuing will be outlined. Representative applications enabled by liquid metal biomaterials from both therapeutic and diagnostic aspects will be pointed out. Potential efforts of employing liquid metals to resolve modern biomedical issues will be discussed. Perspective for future development in liquid metal biomaterials area will be given.

To promote deep understanding of liquid metal in future biomedical applications where hybrid even multiple phase fluids are often involved, this chapter illustrates the unconventional hydrodynamics from experiment, theory, and simulation aspects. Typical phenomena and basic working mechanisms are explained. Some representative simulation methods are incorporated to tackle the governing functions of the electrohydrodynamics. Further, prospects and challenges are raised, which is to offer a startup insight into the new physics of the hybrid fluid under applied fields.

This chapter presents an overview on typical electrical properties of liquid metal in making soft or flexible printed biomedical electronics. The core manufacturing material—the room temperature liquid metal was particularly focused for illustration purpose. Meanwhile, a series of recently developed manufacturing technologies spanning from personal electronic circuit printing to 3D room temperature liquid metal printing were comprehensively introduced. Applications of these planar or three-dimensional printing technologies and the related liquid metal alloy inks in making flexible electronics were briefly discussed. The significantly different adhesions of liquid metal inks on various substrates under different oxidation degrees, un-firmness of circuits, difficulty of fabricating high-accuracy device and low rate of good product which challenge current liquid metal flexible printed electronics were interpreted. Prospects of liquid metal electronics to develop ending user biomedical devices and more extensive applications in the coming daily life were given.

Mechanical properties of liquid metal are significant for various applications in biomedical category. This chapter investigates several classical mechanical issues of bone tissue and typical liquid metal biomaterials. Besides the changes in compositions and ratios of the alloy, representative methods for modifying liquid metal after solidified such as reinforcing with nano particles, casting with different processing technologies etc. are explained. Experimental ways to test mechanical performance and improvement of the low melting point metals were discussed.

This chapter summarizes the fabrication methods and characterizations of the functional liquid metal biomaterials. The future outlooks, including challenges, routes and related efforts, were illustrated and interpreted.

This chapter is to illustrate the use of liquid metal as a high quality image contrast agent for the coming angiography. Characteristics of liquid metal as vascular contrast agent were evaluated. Typical examples of liquid metal angiography and its applications in reconstruction of vascular network were presented. Quantitative comparison regarding the practices between traditional and liquid metal contrast agents was performed.

This chapter illustrates a new conceptual vascular embolization therapy enabled by the liquid metal materials. Several typical experiments on in vivo animal vasculatures were presented to illustrate the evidences of the method in destroying the targeted tissues. Through appropriate administration, the liquid metal embolization is able to destruct the target regions which might starve the tumors to death through a relatively easy way. Meanwhile, theoretical valuation regarding the tumor growth with zero, partial or complete filling of the metal agent inside the vessels were also given to evaluate the liquid metal starvation therapy effects.

In clinics, a medical device is defined as implantable if it is either partly or totally introduced, surgically or medically into the human body and is intended to remain there after the procedure. By virtue of characteristics of well controlled wettability, high electrical conductivity, low cost and easy operation, liquid metal materials have been developed into above area in recent years. In this chapter, representative strategies to develop liquid metals as implantable or injectable medical electronics were introduced and discussed.

Based on the favourable fluidity, super compliance and high electrical conductivity, liquid metal has been developed for nerve reconnection and repairing due to its owned similar electrical properties to nerve. This chapter explains the basic principle to mold liquid metal as an unconventional medium to help the injured nerve recover the ability to conduct electroneurographic signals. Conceptual experiments on both in vitro and in vivo transected sciatic nerves were given to illustrate the feasibility of liquid-metal based reconnection of damaged nerves.

This chapter illustrates the basic principle to adopt the injectable alloy as bone cement through introducing its unique liquid-solid phase transition mechanism. The fundamental characteristics including the mechanical strength, biocompatibility and phase transition-induced thermal effects of such unconventional alloy cement were provided. Prospects for employing the injectable alloy materials as reversible bone cement to fulfill diverse clinical needs were outlined.

This chapter explains the basic concept of a flexible mechanical joint for making human exoskeleton based on a low-melting-point alloy phase change effect. With the liquid-solid phase change capability, this unique joint can easily switch between its flexible and rigid states. In addition, the liquid metal electrode can be an important highly conductive and super compliant electrode for making artificial muscles with the unique capability of two-dimensional in-plane self-healing. Some of such opportunities were discussed.

This chapter presents the basic principle of the conformal epidermal printed electronics based on the liquid metal to achieve the immediate contact between skin surface and electrode. The remarkable features of the liquid metal skin electronics, such as high conformability, good conductivity, better signal stability and fine biocompatibility were discussed. A series of typical applications on disease therapy or health care were given as examples.

This chapter illustrates a series of liquid metal printed biomedical sensor systems, particularly for quantitative measurement of various physiological signals. By virtue of the low melting point, the introduced liquid metal ink makes it possible for the direct writing or printing of the biomedical circuits in a moment. Unlike the prior art, the current fabrication process appears rather straightforward, labor-saving and cost-effective. This is expected to fulfill certain increasing needs in the coming home or society health care. In some cases, the developed sensors have already displayed rather beneficial properties.

This chapter summarizes recent developments in the field of wearable devices where liquid metal technologies may find important contributions. Particular focus was put on potential use of liquid metal electronics in monitoring and therapy for chronic diseases including diabetes, heart disease, Parkinson’s disease, chronic kidney disease and movement disability after neurologic injuries. Meanwhile, typical wearable liquid metal electronics in the emerging applications will be briefly explained. Some key enabling technologies allowing for the implementation of liquid metal enabled wearable monitoring and therapy devices is given, such as miniaturization of electronic circuits, data analysis techniques, telecommunication strategy and physical therapy etc. For the illustration of future developments, research directions worth of pursuing are outlined.

This chapter illustrated the role of alkali liquid metal in developing new generation tumor hyperthermia-chemothermal therapy. The unique merits as offered by the method were outlined. It can be found that the chemothermal therapy based on liquid alkali alloy materials owns a clinical potential to contribute to low cost, safe and effective ablation of tumors, as it can provide truly localized heating through exothermic chemical reactions, possibly even on an outpatient basis.