Spatiotemporal dynamics of nanowire growth in a microfluidic reactor

Mazen Erfan,Tarik Bourouina,Martine Gnambodoe-Capochichi,Yasser M Sabry,Diaa Khalil,Yamin Leprince-Wang

doi:10.1038/s41378-021-00308-4

Abstract

Co-integration of nanomaterials into microdevices poses several technological challenges and presents numerous scientific opportunities that have been addressed in this paper by integrating zinc oxide nanowires (ZnO-NWs) into a microfluidic chamber. In addition to the applications of these combined materials, this work focuses on the study of the growth dynamics and uniformity of nanomaterials in a tiny microfluidic reactor environment. A unique experimental platform was built through the integration of a noninvasive optical characterization technique with the microfluidic reactor. This platform allowed the unprecedented demonstration of time-resolved and spatially resolved monitoring of the in situ growth of NWs, in which the chemicals were continuously fed into the microfluidic reactor. The platform was also used to assess the uniformity of NWs grown quickly in a 10-mm-wide microchamber, which was intentionally chosen to be 20 times wider than those used in previous attempts because it can accommodate applications requiring a large surface of interaction while still taking advantage of submillimeter height. Further observations included the effects of varying the flow rate on the NW diameter and length in addition to a synergetic effect of continuous renewal of the growth solution and the confined environment of the chemical reaction.

Highlights

The integration of nanomaterials into microscale devices opens an avenue of new opportunities[1,2,3,4,5,6,7] that take advantage of the multiple virtues of these devices, both at the nanoscale and microscale[8,9]
We report fast and efficient in situ synthesis and real-time monitoring of NWs grown over intentionally wide, centimeter-scale microfluidic reactors that have all the advantages of micrometric-scale reactors, including the out-of-plane dimension, that is, the microreactor height, as shown schematically in Fig. 1a; in addition, real-time monitoring of the growth kinetics is achieved noninvasively using light
A hydrothermal in situ method is proposed to synthesize zinc oxide nanowires (ZnO-NWs) on seeded silicon (Si) substrate within a microfluidic chip in dynamic mode instead of the static mode previously reported in the literature[13,24,25,45]

Summary

Introduction

The integration of nanomaterials into microscale devices opens an avenue of new opportunities[1,2,3,4,5,6,7] that take advantage of the multiple virtues of these devices, both at the nanoscale and microscale[8,9]. Among the different options for nanomaterials, zinc oxide nanowires (ZnO-NWs) have been selected for ease of growth using soft chemistry They have numerous interesting properties, which makes them a good candidate for novel applications. Several approaches have been utilized to synthesize high-quality ZnO-NWs, such as physical vapor deposition (PVD)[19,20] and chemical vapor deposition (CVD)[21] Many of these techniques are complex and require expensive equipment; in contrast, solution-phase synthesis is an easy and inexpensive way to produce large areas of high-quality ZnO-NWs. Different solution-phase synthesis techniques have been used in the literature, such as electrochemical deposition[22,23], hydrothermal approach[24,25], and sol-gel[26,27], among which hydrothermal growth is one of the easiest and lowest-cost

Methods

Results

Conclusion