Liting Yi

Liquid metal biomaterials: a newly emerging area to tackle modern biomedical challenges

ABSTRACT Conventional biomaterials, such as metals, polymers, composites and ceramics, may not work well when facing certain tough medical challenges. As an alternative, body-temperature liquid metals, such as gallium, or its alloys are recently emerging as new generation functional materials which display many unconventional properties superior to traditional biomaterials, i.e. high fluidity, excellent electrical and thermal conductivities, good biocompatibility, sufficient radiopacity, controllable behaviour, easy manufacture and low cost. This article aims to outline a new biomedical category: liquid metal biomaterials. Representative applications enabled by liquid metal biomaterials from both therapeutic and diagnostic aspects were reviewed. Furthermore, related efforts and perspective for future development of employing liquid metals to resolve modern biomedical tough issues were discussed. With continuous technical progresses and fundamental discoveries, liquid metals are expected to offer more and more outstanding merits as a new class of biomaterials which are promising a generalised way towards resolving biomedical challenges. GRAPHICAL ABSTRACT

A third-order mode high frequency biosensor with atomic resolution.

An atomic resolution ultra-high sensitivity surface acoustic wave (SAW) biosensor for DNA sequences and cells detection is proposed. Interdigitated transducers (IDTs) fabricated on LiNbO3 substrate achieve a high quality factor (Q) of over 4000 at a frequency of 6.4 GHz (third-order harmonic mode) using an optimized design and process. The biosensor shows excellent linear responses to target DNA in the range from 1 μg/ml to 1 ng/ml with a high sensitivity of 6.7 × 10(-16)g/cm(2)/Hz, hence the difference of a single hybridized DNA base can also be distinguished. With such a high mass resolution, the biosensor is capable of quantitative detection of living cancer cells. The frequency responses of single mouse mammary adenocarcinoma (EMT6) cell and mouse fibroblast (3T3) cell are studied. The interferences in the experiments show insignificant influence on the frequency shift, which verifies the high selectivity of the biosensor. The biosensor is also able to repeat the sensing ability after rough cleaning, therefore cost reduction is achieved from the recycling process in practical applications. The detection limit is defined from the noise analysis of the device, atomic resolution is realized according to the calculation, thereby initiating a potential tool for high-precision medical diagnoses and phenomena observation at the atomic-level.

Breathing to harvest energy as a mechanism towards making a liquid metal beating heart

Simulating nature to manufacture a self-powered device or motor has been an important goal in science and engineering. Conventional spontaneous motion has generally been achieved through the Marangoni flow of an organic liquid or water solution. Moreover, as a metallic material mercury has been developed as a beating heart, a kind of self-propulsion example. However, serious safety concerns about mercury restrict its extensive application. This study discovered an important mechanism to realize a GaIn alloy-based liquid metal beating heart by introducing a breathing mechanism in simulating living organisms. With the unique configuration of a semi-submerged liquid metal droplet partially immersed in alkaline solution, such a system produces a surface tension gradient perpendicular to the three-phase contact line which subsequently leads to the oscillation of the droplet and the surrounding solution. This finding suggests a feasible way to fabricate self-oscillating liquid metal motors without input of external electricity or fuels.