Use of Environmental Scanning Electron Microscopy to image poly(N-isopropylacrylamide) microgel particles

García-Salinas, María José; Donald, Athene M.

doi:10.1016/j.jcis.2009.10.064

Cited by 22 publications

(18 citation statements)

References 77 publications

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“…This behavior was reproducible and consistent on both “extruded” and “embedded” versions of the sensor, fabricated via negative (Hydrogen silsesquioxane (HSQ)) and positive (Polymethylmethacrylate (PMMA)) tone resists respectively with e-beam lithography (Figure 5A and 5B). Consistent with prior studies of PNIPAM PNPs by SEM, 36,37,38 dried particles imaged under the negligible humidity conditions of the SEM instrument appear to be widely spaced apart; as we describe above, hydrated particle films were effective at preventing antibody immobilization to these surfaces. While the particles employed in these experiments are too small for us to observe via optical microscopy, an analogously prepared film of larger particles assembled around nanoscale features and observed at ambient laboratory humidity shows that they indeed pack closely (supplementary information), consistent with the blocking ability of particle films.…”

Section: Resultssupporting

confidence: 86%

Enhancing the Detection Limit of Nanoscale Biosensors via Topographically Selective Functionalization

2013

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Nanoscale biosensors have remarkable theoretical sensitivities, but often suffer from sub-optimal limits of detection in practice. This is in part because the sensing area of nanoscale sensors is orders of magnitude smaller than the total device substrate. Current strategies to immobilize probes (capture molecules) functionalize both sensing and non-sensing regions, leading to target depletion and diminished limits of detection. The difference in topography between these regions on nanoscale biosensors offers a way to selectively address only the sensing area. We developed a bottom-up, topographically selective approach employing self-assembled poly(N-isopropylacrylamide) (PNIPAM) hydrogel nanoparticles as a mask to preferentially bind target to only the active sensing region of a photonic crystal (PhC) biosensor. This led to over one order of magnitude improvement in the limit of detection for the device, in agreement with finite element simulations. Since the sensing elements in many nanoscale sensors are topographically distinct, this approach should be widely applicable.

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Section: Resultssupporting

confidence: 86%

Enhancing the Detection Limit of Nanoscale Biosensors via Topographically Selective Functionalization

2013

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“…To observe a phase separation, the terpolymer AM‐NaAA‐DNDA was dissolved in the degassed and distilled water as a solution (wt% = 300 mg/L) 26, 27. The scanning electron microscope images were made by S‐3000 N SEM (Hitachi, Japan).…”

Section: Resultsmentioning

confidence: 99%

“…To observe a phase separation, the terpolymer AM-NaAA-DNDA was dissolved in the degassed and distilled water as a solution (wt% ¼ 300 mg/L). 26,27 The scanning electron microscope images were made by S-3000 N SEM (Hitachi, Japan). The resolution of the SEM was 3 lm, and the magnifying multiple ranges from 3 to 30,000 and analysis was achieved at 20 kV of acceleration voltage and 120-500 Pa of pressure in the sample chamber.…”

Section: Environmental Scanning Electron Microscope (Esem) Imagesmentioning

confidence: 99%

A water‐soluble acrylamide hydrophobically associating polymer: Synthesis, characterization, and properties as EOR chemical

Lai

Dong

et al. 2012

J of Applied Polymer Sci

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A water-soluble acrylamide hydrophobically associating terpolymer for polymer flooding was successfully synthesized via free radical polymerization using acrylamide (AM), acrylic acid (AA), and N,N-divinylnonadeca-1,10-dien-2-amine (DNDA) as raw materials. The terpolymer was characterized by IR spectroscopy and fluorescence spectra. Compared with partially hydrolyzed polyacryamide (HPAM), the terpolymer showed a stronger link and better dimensional network structure under the environmental scanning electron microscope (ESEM). The results of rheology indicated that the terpolymer (AM-NaAA-DNDA) showed an excellent shear-resistance in high shear rate (1000 s À1 ) and remarkable temperature-tolerance (above 110 C). The salt-resisting experiment revealed that this terpolymer had a better anti-salt ability. According to the core flooding test, it could be obtained that oil recovery was enhanced more than 15% under conditions of 2000 mg/L terpolymer in the mineralization of 8000 mg/L at 60 C.

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“…In order to observe the films with higher resolution, environmental scanning electron microscopy (eSEM) was performed on the silicon substrate after film deposition. This technique permits SEM measurements in finite humidity and pressure, p . In Figure f, a monolayer of PNIPAM particles can be clearly seen with neck‐like connections between many neighboring particles, which we identify as interparticle cross‐links.…”

Section: Resultsmentioning

confidence: 97%

Temperature‐Sensitive Hydrogel‐Particle Films from Evaporating Drops

Still

Yunker

Hanson

et al. 2015

Adv Materials Inter

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that was initially suspended. This highly nonuniform deposition is known as the coffee-ring effect; it is produced when the drop edges are pinned during evaporation and subsequent radial capillary fl ows from the drop center carry suspended solutes to the drop perimeter. [5][6][7] The coffeering effect, however, can be ameliorated in aqueous systems of large (>10 µm) suspended spheres, [ 8 ] in suspensions of ellipsoidal particles with strong capillary interactions, [ 9 ] via electrowetting, [ 10 ] in systems with strong attractive forces between particles and substrate, [ 11 ] and in the presence of surfactants that lead to strong Marangoni fl ows, [ 12,13 ] among other techniques. [14][15][16] In these cases, the drying drop system provides experimenters with an opportunity to make uniform thin particle coatings and fi lms.The present contribution builds on investigations of Horigome and Suzuki, which demonstrated that drying aqueous suspensions of PNIPAM particles on polystyrene substrates did not yield typical coffee-ring deposition. [ 17 ] Rather, the hydrogel particles tend to act as amphiphilic moieties, populating the air-water interface fairly uniformly during evaporation. [ 18 ] This behavior, also observed for linear PNIPAM polymers, [ 19,20 ] induces a predominantly uniform deposition of hydrogel particles on the substrate. In our work, we employ micrometersize (diameter d = 1-4 µm) PNIPAM microgel particles with comonomer 2-aminoethylmethacrylate hydrochloride (AEMA) in the suspension. Importantly, the AEMA comonomer introduces primary amine groups onto the microgel particle surfaces that can be used for subsequent cross-linking. Much smaller (<100 nm) PNIPAM particles are feasible, [ 21 ] but systematic studies on the introduction of amine groups still have to be performed. On the other end of the spectrum, we can prepare functionalized particles with amine groups up to approximately 10 µm with the referenced methods. Even larger particles are achievable using microfl uidic techniques.After the water has evaporated, a mostly uniform microgel particle fi lm remains on the substrate. It is kept untouched for another 24 h to ensure cross-linking of neighboring particles by glutaraldehyde that is also mixed into the original droplet suspension. The resultant hydrogel-particle fi lm is temperature-sensitive because the hydrogel particles that compose it are temperature-sensitive. Thus, fi lm size, shape, porosity, and even optical properties are readily varied with temperature control.Our novel responsive fi lms can be utilized as membranes that differ from fi lm structures that have been previously A simple method to prepare temperature-sensitive fi lms composed of micrometer-sized colloidal hydrogel particles using evaporating drops of colloidal suspensions is demonstrated. The fi lms range in thickness from a monolayer to approximately fi fty particle diameters depending on initial particle volume fraction. Sessile droplets of hydrogel-particle suspensions are evaporated on silicon wafers. The fi lm i...

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Use of Environmental Scanning Electron Microscopy to image poly(N-isopropylacrylamide) microgel particles

Cited by 22 publications

References 77 publications

Enhancing the Detection Limit of Nanoscale Biosensors via Topographically Selective Functionalization

Enhancing the Detection Limit of Nanoscale Biosensors via Topographically Selective Functionalization

A water‐soluble acrylamide hydrophobically associating polymer: Synthesis, characterization, and properties as EOR chemical

Temperature‐Sensitive Hydrogel‐Particle Films from Evaporating Drops

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