Determination of Factors Influencing the Wet Etching of Polydimethylsiloxane Using Tetra‐n‐butylammonium Fluoride

Abstract

Polydimethyl siloxane (PDMS) is the most widely used polymer in microfl uidic devices. Microfl uidic devices are used in all ranges of science. The microstructure of a microfl uidic device infl uences its effi ciency. One method for controlling microstructure is through wet etching. A particularly common etchant is tetrabutylammonium fl uoride (TBAF). This report shows that the etching rate of PDMS by a TBAF solution is controlled by the solvent in use. This report presents that solvent dictates interplay between the reactivity of the naked fl uoride with the Si O bonds in the polymer chain and the solubility of the polymer chains. Both high reactivity and accessibility are necessary for a high etching rate. This gives a simple method to control the etching rate of PDMS and by that the microstructure of the microfl uidic device.Dr. M. Kleiman, K. A. Ryu, Prof. A. P. Esser-Kahn Chemistry Department Natural Sciences II Irvine, CA 92697 , USA E-mail: aesserka@uci.edu One of the most common wet etchants for PDMS is tetrabutylammonium fl uoride (TBAF) [19][20][21] -owing to its rapid generation of "naked" fl uoride. Previously, researchers controlled the etching rate of PDMS by varying the fl ow rate and the concentration of TBAF. [ 22 ] They reported a maximum increase of 100% in etching rate by increasing fl ow rate as well as a structural change that depended on TBAF concentration. Here we show an increased etching rate of PDMS, up to two orders of magnitude, by changing the solvent. In these experiments, we use circular 3D channels and characterize the etching rate of the channels using TBAF dissolved in 16 common, organic solvents. Etching of PDMS by TBAF is currently thought to be mediated by the attack of the Si -O bonds of PDMS by the naked fl uoride. [23][24][25] The exact mechanism for the reaction between the naked fl uoride and the Si -O bonds remains unknown. From our current etching experiments, we demonstrate that the wide range of PDMS removal rates depends on two factors: (1) the reactivity of TBAF with Si -O bonds in the solvent, which in turn depends on the polarity of the solvent and (2) the degree of solvent swelling of PDMS.

Functionalized Sulfide Solid Electrolyte with Air-Stable and Chemical-Resistant Oxysulfide Nanolayer for All-Solid-State Batteries

“…In particular, OScA showed a considerably smaller decrease in σ ion than PriA in ACN-based and EA-based solutions, which are more polar than xylene (polar indices of ACN, EA, and xylene are 5.8, 4.4, and 2.5, respectively). 38 , 39 Unlike typical sulfide SEs that show structural degradation owing to the nucleophilic attack of highly polar solvents, 36 , 40 − 42 the OScA material exhibited some resistance to both solvents and binders. This is because the oxysulfide nanolayer formed on the powder surface effectively suppressed the direct chemical reaction between the sulfides and organics, including the solvent and binder.…”

In Situ FT‐IR Spectroscopy Investigation of the Water Sorption of Amphiphilic PDMS Crosslinked Networks

“…The use of a low amount (2.5 wt%) of crosslinker was shown to enable retention of the elastomeric character of the PDMS matrix with a low Young modulus (<1 MPa) . TBAF was found to favor very actively the condensation reaction compared to traditional catalysts, such as tin and bismuth catalysts. Rapid crosslinking in fact occurred at room temperature and curing was eventually completed at 120 °C for 1 h.…”

Optimizing the Extraction of Phenolic Compounds with High Anti-oxidant Activity from Mango Seed Kernel Wastes Using Response Surface Methodology

“…In addition, the use of an ethanol-water system would allow simultaneous extraction of most phenolic compounds present in MSK. Another factor that would explain the results is related to the type and nature of ethanol and water as solvent system [42]. A comparison of polarity indices show that water tends to have a higher degree of interaction with phenolic compounds than ethanol.…”