Relative Humidity Sensors Based on an Environment-Sensitive Fluorophore in Hydrogel Films

Abstract

A fluorescence-based sensing scheme exploiting an environment-sensitive fluorophore embedded in a hydrogel has been developed for measurement of relative humidity (RH). The fluorophore, dapoxyl sulfonic acid (DSA), is incorporated into two different hydrogel films, agarose and a copolymer of acrylamide and 2-(dimethylamino)ethyl methacrylate (DMAEM) cross-linked with N,N'-methylenebisacrylamide. The swelling and contracting of the hydrogels in response to relative humidity alters the polarity of the environment of DSA, stimulating a shift in the emission wavelength. From 0 to 100% RH, acrylamide-DMAEM sensors exhibited a 40 and 15 nm wavelength shift in still air and flowing gas, respectively. Agarose sensors showed a 40 nm wavelength shift from 0 to 100% RH in still air and a 30 nm shift from 0 to 70% RH in flowing gas. Response times for both sensors were 15 min in still air and less than 5 min in flowing gas. The sensing approach is straightforward and cost-effective, yields sensors with characteristics suitable for commercial measurement of RH (i.e., sensitivity, response times, reproducibility), and allows ease of adaptability to specific RH measurement requirements. The results support the potential extension of the method to a wide variety of analytes in the vapor phase and aqueous solution by incorporation of functionalized "smart" hydrogels.

Inkjet‐Printable Amphiphilic Polydiacetylene Precursor for Hydrochromic Imaging on Paper

“…The solution was stirred at ambient temperature overnight and concentrated in vacuo to give a residue that was subjected to a silica gel column chromatography (methylene chloride/methanol, 96/4) to give the desired product as yellow liquid (0.57 g, 77%). 1 Inkjet Printing of DA-1 : Black ink was removed from a cartridge (HP 703) of a commercial inkjet printer (HP Deskjet Ink Advantage K209g). After washing with ethanol and water, the cartridge was dried with nitrogen purging.…”

“…These materials have found great utility in sensing humidity [1][2][3][4][5][6][7][8][9][10][11][12] and measuring the water contents of organic solvents. [13][14][15][16][17][18] Designs of hydrochromic humidity sensors can be based on conjugated organic molecules that undergo color changes associated with polarity changes caused by exposure to water.…”

“…[13][14][15][16][17][18] Designs of hydrochromic humidity sensors can be based on conjugated organic molecules that undergo color changes associated with polarity changes caused by exposure to water. [ 1,2 ] Certain periodically ordered polymer fi lms, which have refl ectance wavelengths that the interchain distance in this polymer leads to partial distortion of the arrayed p-orbitals and an associated change in the wavelength maximum for visible light absorption. Importantly, exceedingly small quantities of water secreted from sweat pores are suffi cient to promote an instantaneous colorimetric transition of the polymer.…”

Cavitation in a swollen elastomer constrained by a non-swellable shell

“…Recently, swelling elastomers have been intensively explored in diverse applications, ranging from swellable packers in oil field 1 to soft actuators and sensors. [2][3][4][5][6] In the applications of swollen elastomer, different mechanical instabilities have been observed and studied. For instance, it has been shown that creases, a newly identified mechanical instability mode, can form on the surface of a constrained swelling gel when its swelling ratio is beyond a critical value.…”

Permeability characterization of hydroxypropylcellulose/ polyacrylonitrile blend membranes

“…Gawel paid attention to synthesizing novel materials, he grafted sulfobetaine side onto HPC backbone, and found that the novel polymers did not interact with model anionic, cationic and zwitterionic surfactants, and were resistant to proteins adhesion, so they can be used for preparation of antiadhesive surface [7]. Mucha and his research groups studied the water adsorption on 2 chitosan film and on its blend films of chitosan and HPC, described the isotherms of water adsorption in resultant films [8].The investigation of antibacterial activity of HPC films associated with chitosan exhibited an excellent inhibition on solid medium [9].…”