OpenHumidistat: Humidity-controlled experiments for everyone

Veldscholte, Lars B.; Beer, Sissi de

doi:10.1016/j.ohx.2022.e00288

Cited by 6 publications

(7 citation statements)

References 15 publications

(5 reference statements)

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“…Woollam M-2000X spectroscopic ellipsometer with a 5 mL heated liquid cell (J.A. Woollam) connected to an OpenHumidistat 38 humidity controller. The cell’s heating feature is not used.…”

Section: Methodsmentioning

confidence: 99%

Vapor Swelling of Polymer Brushes Compared to Nongrafted Films

et al. 2022

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Polymer brushes, coatings of polymers covalently end-grafted to a surface, have been proposed as a more stable alternative to traditional physisorbed coatings. However, when such coatings are applied in settings such as vapor sensing and gas separation technologies, their responsiveness to solvent vapors becomes an important consideration. It can be anticipated that the end-anchoring in polymer brushes reduces the translational entropy of the polymers and instead introduces an entropic penalty against stretching when vapor is absorbed. Therefore, swelling can be expected to be diminished in brushes compared to nongrafted films. Here, we study the effect of the anchoring-constraint on vapor sorption in polymer coatings using coarse-grained molecular dynamics simulations as well as humidity-controlled ellipsometry on chemically identical polymer brushes and nongrafted films. We find a qualitative agreement between simulations and experiments, with both indicating that brushes certainly swell less than physisorbed films, although this effect is minor for common grafting densities. Our results imply that polymer brushes indeed hold great potential for the intended applications.

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“…Woollam M-2000X spectroscopic ellipsometer with a 5 mL heated liquid cell (J.A. Woollam) connected to an OpenHumidistat 38 humidity controller. The cell’s heating feature is not used.…”

Section: Methodsmentioning

confidence: 99%

Vapor Swelling of Polymer Brushes Compared to Nongrafted Films

et al. 2022

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“…Data processing, analysis, and visualization were performed using Python, with NumPy, SciPy, and Matplotlib . The Python code, e.g., to parse LAMMPS ave/chunk output or to extract contact angles from droplets, is made available online …”

Section: Discussionmentioning

confidence: 99%

“…57 The Python code, e.g., to parse LAMMPS ave/chunk output or to extract contact angles from droplets, is made available online. 58 ■ RESULTS AND DISCUSSION First, we will look at the contact angle of a droplet on a polymer brush as a function of polymer−liquid affinity for several values of the brush grafting density. Next, we address the pressure anisotropy profiles of brushes and films and examine the influence of the integration limit on the interfacial tensions and resulting Young's contact angle.…”

Section: ■ Model and Methodsmentioning

confidence: 99%

Pressure Anisotropy in Polymer Brushes and Its Effects on Wetting

Veldscholte,

Snoeijer,

den Otter

et al. 2024

Langmuir

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Polymer brushes, coatings consisting of densely grafted macromolecules, experience an intrinsic lateral compressive pressure, originating from chain elasticity and excluded volume interactions. This lateral pressure complicates a proper definition of the interface and, thereby, the determination and interpretation of the interfacial tension and its relation to the wetting behavior of brushes. Here, we study the link among grafting-induced compressive lateral pressure in polymer brushes, interfacial tension, and brush wettability using coarse-grained molecular dynamics simulations. We focus on grafting densities and polymer−liquid affinities such that the polymer and liquid do not tend to mix. For these systems, a central result is that the liquid contact angle is independent of the grafting density, which implies that the graftinginduced lateral compressive pressure in the brush does not influence its wettability. Although the definition of brush interfacial tensions is complicated by the grafting-induced pressure, the difference in the interfacial tension between wet and dry brushes is perfectly well-defined. We confirm explicitly from Young's law that this difference offers an accurate description of the brush wettability. We then explore a method to isolate the grafting-induced contribution to the lateral pressure, assuming the interfacial tension is independent of grafting density. This scenario indeed allows disentanglement of interfacial and grafting effects for a broad range of parameters, except close to the mixing point. We separately discuss the latter case in light of autophobic dewetting.

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“…We apply two sets of gas flowmeters to dilute the calibrating gas about three orders to reach tens of ppb concentrations for some gases. The simpler, cheaper, but much less accurate method of generating vapors uses a glass bubbler with a liquid compound evaporating because the flowing S.A. Gas concentration can be estimated depending on S.A. flow rate and the compound liquid’s vapor pressure [ 95 ]. The presented gas setup does not introduce humidity into the generated gas mixture, but a homemade humidifier can be applied to the gas setup to control humidity level precisely [ 96 ].…”

Section: Methodsmentioning

confidence: 99%

Flicker Noise in Resistive Gas Sensors—Measurement Setups and Applications for Enhanced Gas Sensing

Smulko,

Scandurra,

Drozdowska

et al. 2024

Sensors

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We discuss the implementation challenges of gas sensing systems based on low-frequency noise measurements on chemoresistive sensors. Resistance fluctuations in various gas sensing materials, in a frequency range typically up to a few kHz, can enhance gas sensing by considering its intensity and the slope of power spectral density. The issues of low-frequency noise measurements in resistive gas sensors, specifically in two-dimensional materials exhibiting gas-sensing properties, are considered. We present measurement setups and noise-processing methods for gas detection. The chemoresistive sensors show various DC resistances requiring different flicker noise measurement approaches. Separate noise measurement setups are used for resistances up to a few hundred kΩ and for resistances with much higher values. Noise measurements in highly resistive materials (e.g., MoS2, WS2, and ZrS3) are prone to external interferences but can be modulated using temperature or light irradiation for enhanced sensing. Therefore, such materials are of considerable interest for gas sensing.

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OpenHumidistat: Humidity-controlled experiments for everyone

Cited by 6 publications

References 15 publications

Vapor Swelling of Polymer Brushes Compared to Nongrafted Films

Vapor Swelling of Polymer Brushes Compared to Nongrafted Films

Pressure Anisotropy in Polymer Brushes and Its Effects on Wetting

Flicker Noise in Resistive Gas Sensors—Measurement Setups and Applications for Enhanced Gas Sensing

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