Anayet Ullah Siddique | Washington State University (original) (raw)
Papers by Anayet Ullah Siddique
arXiv (Cornell University), Sep 22, 2023
• Surface nanobubble patterning using focused ion beam (FIB) technique. • Nanobubbles selectively... more • Surface nanobubble patterning using focused ion beam (FIB) technique. • Nanobubbles selectively positioned on hydrophobic domains. • Location of surface nanobubbles regulated by nanostructured surfaces. • Effect of FIB patterning on morphology of nanobubble including contact angle analyzed.
ACS Langmuir, 2024
Surface nanobubbles forming on hydrophobic surfaces in water present an exciting opportunity as p... more Surface nanobubbles forming on hydrophobic surfaces in water present an exciting opportunity as potential agents of top-down and bottom-up nanopatterning. The formation and characteristics of surface nanobubbles are strongly influenced by the physical and chemical properties of the substrate. In this study, focused ion beam (FIB) milling is used for the first time to spatially control the nucleation of surface nanobubbles with 75 nm precision. The spontaneous formation of nanobubbles onalternating lines of a self-assembled monolayer (octadecyltrichlor-osilane) patterned by FIB is detected by atomic force microscopy. The effect of chemical vs topographical surface heterogeneity onthe formation of nanobubbles is investigated by comparing sampleswith OTS coating applied pre- vs post-FIB patterning. The resultsconfirm that nanoscale FIB-based patterning can effectively control surface nanobubble position by means of chemical heterogeneity. The effect of FIB milling on nanobubble morphology and properties, including contact angle and gas oversaturation, is also reported. Molecular dynamics simulations provide further insight into the effects of FIB amorphization on surface nanobubble formation. Combined experimental and simulation investigations offer insights to guide future nanobubble-based patterning using FIB milling.
Volume 7: Fluids Engineering, 2019
Droplet-wall impacts are well known to produce a wide variety of outcomes such as spreading, spla... more Droplet-wall impacts are well known to produce a wide variety of outcomes such as spreading, splashing, jetting, receding, and rebounding from hydrophobic and superhydrophobic surfaces. In this work, we focus on the growth of jets that form during the partial recoil of liquid droplets that impinge upon hydrophilic substrates composed of cylindrical micro-pillars of various dimensions and distributions (i.e., height, width, pillar spacing, etc.). Micro-pillars are fabricated on the hydrophilic silicon wafers by standard microfabrication processes, including metal etch mask patterning by photolithography, metal deposition, and lift-off to achieve the designed pillar shapes and spacing, and followed by dry etching for various pillar heights. Micrometer-sized drops of glycerol mixtures impacting micro-structured wafers are investigated using high-speed video photography. Impact velocities are varied to observe the influence of Weber number on the dynamic properties of the rebounding jet...
The jetting phenomenon associated with droplet impact upon a hydrophilic micropillared substrate ... more The jetting phenomenon associated with droplet impact upon a hydrophilic micropillared substrate was analyzed in detail using a high-speed camera. Viscosities of the fluids were varied using differing concentrations of glycerol in deionized water. This paper aims to connect similarities between this form of capillary jetting and another well-known jetting phenomenon from the bubble bursting. Both experience a cavity collapse when opposing fluid fronts collide which causes a singularity at the liquid surface, thus leading to the occurrence of jetting. Following processes used to define scaling laws for bubble bursting, a similar approach was taken to derive scaling laws for the dimensionless jet height, jet radius, base height, and radius of the jet base with respect to dimensionless time for the jetting phenomenon associated with the droplet impact. The development of a top droplet before the breakup of the jet also allows the examination of a scaling law for the necking diameter. W...
arXiv (Cornell University), Sep 22, 2023
• Surface nanobubble patterning using focused ion beam (FIB) technique. • Nanobubbles selectively... more • Surface nanobubble patterning using focused ion beam (FIB) technique. • Nanobubbles selectively positioned on hydrophobic domains. • Location of surface nanobubbles regulated by nanostructured surfaces. • Effect of FIB patterning on morphology of nanobubble including contact angle analyzed.
ACS Langmuir, 2024
Surface nanobubbles forming on hydrophobic surfaces in water present an exciting opportunity as p... more Surface nanobubbles forming on hydrophobic surfaces in water present an exciting opportunity as potential agents of top-down and bottom-up nanopatterning. The formation and characteristics of surface nanobubbles are strongly influenced by the physical and chemical properties of the substrate. In this study, focused ion beam (FIB) milling is used for the first time to spatially control the nucleation of surface nanobubbles with 75 nm precision. The spontaneous formation of nanobubbles onalternating lines of a self-assembled monolayer (octadecyltrichlor-osilane) patterned by FIB is detected by atomic force microscopy. The effect of chemical vs topographical surface heterogeneity onthe formation of nanobubbles is investigated by comparing sampleswith OTS coating applied pre- vs post-FIB patterning. The resultsconfirm that nanoscale FIB-based patterning can effectively control surface nanobubble position by means of chemical heterogeneity. The effect of FIB milling on nanobubble morphology and properties, including contact angle and gas oversaturation, is also reported. Molecular dynamics simulations provide further insight into the effects of FIB amorphization on surface nanobubble formation. Combined experimental and simulation investigations offer insights to guide future nanobubble-based patterning using FIB milling.
Volume 7: Fluids Engineering, 2019
Droplet-wall impacts are well known to produce a wide variety of outcomes such as spreading, spla... more Droplet-wall impacts are well known to produce a wide variety of outcomes such as spreading, splashing, jetting, receding, and rebounding from hydrophobic and superhydrophobic surfaces. In this work, we focus on the growth of jets that form during the partial recoil of liquid droplets that impinge upon hydrophilic substrates composed of cylindrical micro-pillars of various dimensions and distributions (i.e., height, width, pillar spacing, etc.). Micro-pillars are fabricated on the hydrophilic silicon wafers by standard microfabrication processes, including metal etch mask patterning by photolithography, metal deposition, and lift-off to achieve the designed pillar shapes and spacing, and followed by dry etching for various pillar heights. Micrometer-sized drops of glycerol mixtures impacting micro-structured wafers are investigated using high-speed video photography. Impact velocities are varied to observe the influence of Weber number on the dynamic properties of the rebounding jet...
The jetting phenomenon associated with droplet impact upon a hydrophilic micropillared substrate ... more The jetting phenomenon associated with droplet impact upon a hydrophilic micropillared substrate was analyzed in detail using a high-speed camera. Viscosities of the fluids were varied using differing concentrations of glycerol in deionized water. This paper aims to connect similarities between this form of capillary jetting and another well-known jetting phenomenon from the bubble bursting. Both experience a cavity collapse when opposing fluid fronts collide which causes a singularity at the liquid surface, thus leading to the occurrence of jetting. Following processes used to define scaling laws for bubble bursting, a similar approach was taken to derive scaling laws for the dimensionless jet height, jet radius, base height, and radius of the jet base with respect to dimensionless time for the jetting phenomenon associated with the droplet impact. The development of a top droplet before the breakup of the jet also allows the examination of a scaling law for the necking diameter. W...