Studying kinetics of a surface reaction using elastocapillary effect

Singh, Nitish Kumar; Kumar, Ashok; Ghatak, Ajoy

doi:10.1016/j.jcis.2023.04.103

Cited by 2 publications

(2 citation statements)

References 30 publications

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“…Finally, it is worth pointing out that there are many examples of physical processes being powered by excess surface free energy. For example, surface free energy born out of coalescence of two liquid drops in motion has been shown to increase the speed, i.e., the kinetic energy, of the resultant drop; similarly, excess interfacial energy resulting from wetting of the curved surface of a soft solid has been shown to induce deformation in it. , In contrast, the phenomenon presented here is an example of a chemical reaction, the rate of which is influenced by the excess surface energy. This effect may be relevant for several practical situations: for example, for catalyst- or enzyme-mediated reactions, a soft support can possibly enhance the reaction rate compared to what is conventionally achieved.…”

Section: Discussionmentioning

confidence: 83%

Enhancement of the Rate of Surface Reactions by the Elastocapillary Effect

Singh,

Ghatak

2024

Langmuir

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We examined the effect of deformability of a solid substrate on the kinetics of a surface reaction that occurs between chemical species present in it and a liquid dispensed on it. In particular, we have dispensed aqueous solutions of gold and silver salt as sessile drops or as a liquid pool on a cross-linked film of poly(dimethylsiloxane) (PDMS). The PDMS surface contains organosilane (SiH), which reduces the salt, producing metallic nanoparticles at the solid–liquid interface. These experiments reveal that, for a sufficiently soft solid, the reaction proceeds about three times faster in the drop mode than in the pool mode. The reaction conditions in both cases remain exactly identical except that, for the drop, the vertical component of the liquid surface tension deforms the solid substrate at the three-phase contact line. We have estimated the solid–liquid and solid–air interfacial energy, which along with the surface energy of the liquid gives an estimate of excess free energy. This energy is found to be different for the drop and pool modes. By considering that this excess free energy decreases the activation energy barrier for the reaction, we have shown that the reaction rate constant in the drop mode should indeed exceed that in the pool mode by about three times.

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Section: Discussionmentioning

confidence: 83%

Enhancement of the Rate of Surface Reactions by the Elastocapillary Effect

Singh,

Ghatak

2024

Langmuir

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“…The layer was patterned with tiny pillars. Ecoflex, being an elastic material with Young's modulus, E as low as 0.1 MPa [50], allows large deformability yet reversibility and thus was expected to yield high sensitivity over repeated cycles. Micro-pillars diminish the effective dielectric constant of the layer, enhance its deformability, and thus increase the device's sensitivity.…”

Section: Introductionmentioning

confidence: 99%

Highly sensitive flexible capacitive pressure sensor with structured elastomeric dielectric layers

Rawal,

Ghatak

2024

J. Micromech. Microeng.

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Sensitive yet stable, robust yet flexible and accurate yet energy efficient pressure sensors are required for variety of purposes. While a large variety of designs and dielectric materials have been explored for this purpose, there is still need of a flexible pressure sensor that will allow easy scale up and inexpensive fabrication. To this end, we have presented here the design of a flexible capacitive pressure sensor using copper coated paper as flexible electrodes and soft Ecoflex layers decorated with cylindrical micro-pillars as the dielectric. While microscopic construct of the sensor allows its easy manufacturability, softness of the layer imparts sensitivity to it. In contrast to many conventional sensors, this design yields sensitivity as high as ~5 kPa-1 at pressure < 1 kPa and somewhat smaller sensitivity as pressure exceeds 1 kPa. We have varied systematically pillar diameter, skin thickness of dielectric layer and pitch of the pillar array to optimize the design and demonstrate its easy tunability. We have presented a model based on buckling of the pillars to predict the response of the sensor. We have explored also a specific design that minimizes the hysteresis.

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Studying kinetics of a surface reaction using elastocapillary effect

Cited by 2 publications

References 30 publications

Enhancement of the Rate of Surface Reactions by the Elastocapillary Effect

Enhancement of the Rate of Surface Reactions by the Elastocapillary Effect

Highly sensitive flexible capacitive pressure sensor with structured elastomeric dielectric layers

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