Vapor Mapping in a Microscopic Space with a Scanning Nanoprobe Interferometer

Abstract

Evaporation of a liquid inside a microscopic space plays a key role to drive various natural phenomena or chemical/thermal processes in microfluidic systems. So far, fundamental studies in such fields have been indirect due to the lack of techniques geometrically accessible in microscopic spaces. Here, we report on a nanoprobe interferometer that can directly visualize vapor in 3D (dimensions) in a microscopic space. We first optimize the tip geometry of the nanoprobe to enhance its sensitivity just by analyzing the interference patterns during the nanoprobe growth in real time. Based on scanning with the nanoprobe interferometer, vapor concentration from a water meniscus in a glass microcapillary is experimentally mapped, which leads to the measurement of the local evaporation flux from the meniscus. The evaporation flux increases from the capillary center to the wall and decreases with the capillary diameter, mostly due to the Kelvin effect and strong evaporation at the three-phase contact line. Specifically, the flux at the center follows J v(center) ∝ e–7.7×10–4 d , in sharp contrast to the power-law decrease reported. Our nanotechnological methodology would pave the way to explore various questions associated with microscopic, geometrically confined evaporation dynamics which has been experimentally inaccessible so far.

Recent advances in meniscus-on-demand three-dimensional micro- and nano-printing for electronics and photonics

“…Because a meniscus can be as small as a few micrometers or even a few hundred nanometers, printed stimulus-responsive polymers can serve as micro/nanoscale sensors or actuators. Kim et al developed a highresolution (250 nm) on-demand moisture sensor by exploiting the interferometric response of a 3D-printed PS nanoprobe (figure 5(a)) [70,71]. Won et al used the meniscus-guided 3D printing method to form a stretchable poly(methyl methacrylate)/PPy gas sensor for NH 3 (figure 5(b)) [72].…”

A Multimodal Sensing CMOS Imager Based on Dual‐Focus Imaging

“…Despite some progress, existing multimodal sensing technologies assemble various sensors based on different sensing principles, resulting in bulky system designs, cumbersome signal interfaces, and complex data processing procedures. [ 7 ] These technologies cannot meet the growing complex environment perception demands [ 8 ] of miniaturized devices, such as microrobots [ 9 ] and in vivo medical devices. [ 10 ] Thus, a miniature multimodal sensing platform is urgently needed.…”