Electric current-assisted manipulation of liquid metals using a stylus at micro-and nano-scales

Abstract

A novel methodology, based on wetting and electromigration, for transporting liquid metal, over long distances, at micro-and nano-scale using a stylus is reported. The mechanism is analogous to a dropper that uses “suction and release” actions to “collect and dispense” liquid. In our methodology, a stylus coated with a thin metal film acts like the dropper that collects liquid metal from a reservoir upon application of an electric current, holds the liquid metal via wetting while carrying the liquid metal over large distances away from the reservoir and drops it on the target location by reversing the direction of electric current. Essentially, the working principle of the technique relies on the directionality of electromigration force and adhesive force due to wetting. The working of the technique is demonstrated by using an Au-coated Si micropillar as the stylus, liquid Ga as the liquid metal to be transported, and a Kleindik-based position micro-manipulator to traverse the stylus from the liquid reservoir to the target location. For demonstrating the potential applications, the technique is utilized for closing a micro-gap by dispensing a minuscule amount of liquid Ga and conformally coating the desired segment of the patterned thin films with liquid Ga. This study confirms the promising potential of the developed technique for reversible, controlled manipulation of liquid metal at small length scales.

Controllable Flow and Manipulation of Liquid Metals

“…[212] Meanwhile, LMs can be transported over long distances via electromigration. [213,214] As shown in Figure 10g, a stylus coated with thin LM acts as a dropper, col-lecting liquid metal from a reservoir using an electric current. The stylus then carries the LM over large distances away from the reservoir, holding the liquid metal via wetting.…”

“…[ 211 ] g) LMs transported over long distances via electromigration. [ 214 ] a) Reproduced with permission. [ 41 ] Copyright 2020, American Physical Society.…”

“…g) Reproduced with permission. [214] Copyright 2022, IOP Publishing. oxide layer eventually impedes the fluidity of liquid metals.…”

“…f) Electric field-driven the controllable formation of LMDs [211]. g) LMs transported over long distances via electromigration [214]. a) Reproduced with permission [41].…”

Image quality enhancement of PMUT-based photoacoustic imaging

“…Micro-electro-mechanical systems (MEMS) technology-based piezoelectric micro-machined ultrasound transducer (PMUT), [1][2][3] that can be directly bonded to application-specific integrated circuits (ASICs) with ease − are ideally suited for such miniaturized devices facilitating several unique technological advantageous features such as PMUTs should have a low cost and good reproducibility due to batch fabrication processing, due to reduced power requirements and ease of on-chip integration, reduction in size and weight. [4][5][6] Micromachined Ultrasound Transducers (MUTs) [7][8][9][10] are becoming more common as a replacement for conventional transducers. 11 There has been a recent trend in employing such devices to make low-cost ultra-portable photoacoustic imaging (PAI) systems that will be useful for point-of-care imaging applications and thus complement more conventional imaging technologies like positron emission tomography (PET) and magnetic resonance imaging (MRI) because of its unique and promising technical features − more specifically, not only to achieve higher spatial resolution (∼ 150µm) at the depth ∼ cm for recovery of various and complex tissue pathophysiological information (molecular ([Hb], [HbO 2 ], SO, and total Hb), physical (acoustic and mechanical properties), tissue anatomy or morphology, and micro-vasculature structures non-destructively and non-invasively but also to facilitate development of multi-modality imaging systems 12,13 − that are of utmost clinical importance and thus, significant scientific impact.…”