Electrolyte Ionic Strength Research Articles

PH Sensitivity Estimation in Potentiometric Metal Oxide pH Sensors Using the Principle of Invariance

A numerically solvable engineering model has been proposed that predicts the sensitivity of metal oxide- (MOX-) based potentiometric pH sensors. The proposed model takes into account the microstructure and crystalline structure of the MOX material. The predicted pH sensitivities are consistent with experimental results with the difference below 6% across three MOX (RuO2, TiO2, and Ta2O5) analysed. The model distinguishes the performance of different MOX phases by the appropriate choice of surface hydroxyl site densities and dielectric constants, making it possible to estimate the performance of MOX electrodes fabricated through different high-temperature and low-temperature annealing methods. It further addresses the problem, cited by theoreticians, of independently determining the C1 inner Helmholtz capacitance parameter while applying the triple-layer model to pH sensors. This is done by varying the C1 capacitance parameter until an invariant pH sensitivity across different electrolyte ionic strengths is obtained. This invariance point identifies the C1 capacitance. The corresponding pH sensitivity is the characteristic sensitivity of MOX. The model has been applied across different types of metal oxides, namely, expensive platinum group oxides (RuO2) and cheaper nonplatinum group MOX (TiO2 and Ta2O5). High temperature annealed, RuO2 produced a high pH sensitivity of 59.1082 mV/pH, while TiO2 and Ta2O5 produced sub-Nernstian sensitivities of 30.0011 and 34.6144 mV/pH, respectively. Low temperature annealed, TiO2 and Ta2O5 produced Nernstian sensitivities of 59.1050 and 59.1081 mV/pH, respectively, illustrating the potential of using cheaper nonplatinum group MOx as alternative sensor electrode materials. Separately, the usefulness of relatively less investigated, cheap, and readily available MOX, viz. Al2O3, as the electrode material was analysed. Low-temperature-annealed Al2O3 with a Nernstian sensitivity of 59.1050 mV/pH can be considered as a potential electrode material. The proposed engineering model can be used as a preliminary prediction mechanism for choosing potentially cheaper alternative sensor electrode materials.

Novel Approach toward Electrofluidic Substrates Utilizing Textile-Based Braided Structure.

Electrofluidics is the unique combination of electrophoresis and microfluidics, which has opened up broad opportunities for bioanalysis and multiplexed assay. These systems typically comprise inaccessible and fully enclosed microcapillary or microchannels, with limited sample loading capacities and no direct access to the solutes within. Here, we investigate the application of multiyarn textile assemblies which provides an open and surface accessible electrophoretic separation platform. Three-dimensional (3D) textile structures have been produced using conventional knitting and braiding techniques from a range of commercially available yarns. Capillary zone electrophoresis separation studies have been carried out on these substrates using fluorescent anionic (fluorescence, FL) and cationic (rhodamine-B, Rh-B) markers. The effects of different yarn surface chemistry, textile fabrication technique, and electrolyte ionic strength on the electrophoretic mobility of the test analytes have been studied. From the broad range of yarns investigated, polyester was shown to have the highest electrophoretic mobility for Rh-B (6 × 10-4 cm2 V-1 s-1) and for FL (4 × 10-4 cm2 V-1 s-1). The braiding approach, being simple and versatile, was found to be the most effective route to produce 3D textile-based structures and offered the potential for selective movement and targeted delivery to different channels. Composite braids made with yarns of differential surface chemistries further revealed a unique behavior of separation and parallel movement of oppositely charged ionic species. We also demonstrate the feasibility to apply isotachophoresis (ITP) on these braided textile substrates to rapidly focus dispersed FL sample bands. Here, we demonstrate the focusing of FL from a dispersed band into narrow band with a 400 times reduction in sample width over 90 s. Owing to the simplicity and reproducibility of the developed approach, textile-based inverted microfluidic applications are expected to enable opportunities in bioanalysis, proteomics, and rapid clinical diagnostics.

Surface modified carbon nanomats provide cationic and anionic rectifier membranes in aqueous electrolyte media

Carbon nanofibers (CNFs) are converted into anionic current rectifiers by surface modification with amine functional groups using hydrothermal means (forming modified CNFs, with generation-3 poly (propylene imine) dendrimer, urea and boric acid). To confirm surface charge, morphological changes and carbon nanomat thickness, zeta potential analysis, transmission electron microscopy (TEM) and scanning electron microscopy (SEM), were used. When a dispersion of surface modified carbon nanofibers in DMF is drop-cast asymmetrically to form nanomats onto laser drilled microholes (5, 10, or 20 µm diameter) of poly (ethylene terephthalate) substrates and immersed into aqueous electrolyte solutions, anionic diode behaviour is observed (in contrast to pristine carbon nanofibers, which exhibit cationic diode behaviour). The effects of electrolyte type, ionic strength, and microhole diameter on ionic diode performance were investigated using cyclic voltammetry, chronoamperometry, and impedance spectroscopy. Future applications in desalination are proposed.

A closed-loop detection system based on orthogonal phase locking for EISCAP sensor

Electrolyte-insulator-semiconductor capacitor (EISCAP) is a potentiometric (bio)chemical sensing device based on semiconductor field effect principle. All the (bio)chemical substances giving rise to surface potential reactions can be detected by EISCAP. To improve measuring efficiency, based on orthogonal phase locking mechanism, a new closed-loop detection system for EISCAP sensor is developed. In this paper, principle of the system is presented, and its performance is evaluated. Theoretical and experimental studies indicate, the detection result is almost not affected by fluctuation of electrolyte ionic strength, this closed-loop detection method is more efficient than conventional methods, and the detection performance is favorable.

Counterintuitive Electrostatic Forces in Liposome Colloidal Crystals

We previously studied the repulsive electrostatic forces among like-charged liposomes in deionized water by measuring the shear moduli (rigidity, stiffness) of liposome-water suspensions as a function of liposome charge and concentration (Cohen, Wei & Ou-Yang). The liposomes were extruded, unilamellar, 100 nm, made of weak-acid POPG and zwitterionic POPC mixtures in incremental ratios. At low charge the shear moduli increased with liposome PG content as expected, reaching a maximum at ∼20% PG, then decreased with further increase of PG. At 100% PG the suspension was flaccid with a shear modulus near zero. Our measurements show that in deionized water weakly-charged liposomes interact strongly, and strongly-charged liposomes interact weakly. Here we analyze this counterintuitive finding. We use a Debye-Hückel (DH) Wigner-Seitz (WS) model to calculate electrostatic potentials and electric fields in the suspensions analytically. The unusual bulk behavior arises from a strict correlation, mandated by global electroneutrality, between the deprotonated PG liposome charge and the number of solvated H+ ions in a WS cell. We map the conditions for weak vs. strong inter-liposome forces in terms of the H+ screening length relative to the WS sphere radius, which is a measure of the mean distance between liposomes. The H+ screening length depends on the solvated H+ mean concentration, hence on the net liposome charge including charge-regulation effects. The liposome surface potentials are shown to be small, which justifies use of the DH approximation. We plot electrostatic-potential and pH profiles in a WS cell as a function of the liposome PG/PC ratio, calculate PG/PC at the crossover from strong to weak coupling, and determine the added-salt concentration required to mask the above effects. These results may be relevant to protein-protein interactions in low ionic-strength electrolytes.

Chemically modified electrode based on dihexadecyl hydrogen phosphate and carbonaceous materials: improvement of analytical and electrochemical features applied to uranium determination

This work deals about the evaluation and improvement of analytical and electrochemical features of chemically modified electrode based on dihexadecyl hydrogen phosphate (DPH) and carbonaceous materials. The electrochemical features of films obtained were evaluated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Between the modifications evaluated, the glassy carbon electrode (GCE) modified with CB and DPH (DHP-CB/GCE) showed lower resistance to charge transfer and higher electron transfer rate. Additionally, the highest current of U(VI) was obtained with DHP-CB/GCE in a very stable way, the process present quasi-reversible behavior and it is controlled by a mixture of diffusion and absorption. The best instrumental conditions for U(VI) determination were obtained applying frequency of 15 Hz, amplitude of 100 mV, and deposition potential of − 0.1 V (by square wave cathodic stripping voltammetry). Among the electrolyte compositions (acetate and citrate buffers), ionic strength (from 0.10, 0.15, to 0.20 mol L−1), and pH (from 3.6 to 5.6) evaluated, the highest current of U(VI) were obtained in 0.15 mol L−1 of acetate buffer, pH 5.6. The method was accurate, linear, and sensitive (detection limit of 0.088 μg L−1 using 300 s of deposition).

Measurements of the Electric Conductivity of MWCNT Suspension Electrodes with Varying Potassium Bromide Electrolyte Ionic Strength

Suspension electrodes are under intense investigation due to their use in electrochemical systems such as redox flow batteries, capacitive deionization cells and flow supercapacitors. They provide novel functionalities not available with static electrodes, such as spatial power-energy decoupling for flow hybrid batteries, and continuous water desalination by capacitive deionization cells. Yet their electric conductivity is low relative to static electrodes made of the same material. It was previously found that suspension electrodes employing multi-walled carbon nanotubes (MWCNTs) demonstrate among the highest electric conductivities in deionized water, yet the effect of electrolyte ionic strength on their electric conductivity of was not elucidated. We here measure the electric conductivity of MWCNTs suspensions in a KBr electrolyte under flow using two- and four-electrode setups with alternative and direct current (DC) techniques. Only the two-electrode DC technique measured solely electronic conductivity, while all the other techniques measured the combined ionic and electronic conductivity. The electronic conductivity increased with MWCNT concentration in accordance with percolation theory power law. It increased also with electrolyte concentration by one to two orders of magnitude, with the critical exponent value transitioning from ∼2 to ∼1 with the increasing KBr concentration, which was explained in terms of the Derjaguin-Landau-Verwey-Overbeek theory.

Adsorption of Carboxymethyl Cellulose onto Titania Particle Films Studied with in Situ IR Spectroscopic Analysis.

Adsorption of carboxymethyl cellulose (CMC) in aqueous solution onto a titania nanoparticle film has been studied using in situ attenuated total reflectance infrared spectroscopy (ATR-IR). CMC was adsorbed onto the positively charged titania surface in neutral, partially charged, and fully charged state. The response of the adsorbed polyelectrolyte layer was monitored upon changing the electrolyte pH and ionic strength. The degree of dissociation of the CMC increased upon adsorption onto the titania surface and changed with the surface coverage. Ionic strength change was observed to influence the degree of dissociation of the adsorbed CMC similar as when in solution. No significant peak shifts were observed in the spectrum of the adsorbed CMC during adsorption or in response to changing solution conditions; therefore, inner-sphere complexation between the carboxyl groups and the titania could not be confirmed. The effect of ion identity on the adsorption process was studied using soft and hard cations and mono- and divalent cations. The presence of a divalent counterion was observed to cause changes in the carboxymethyl vibrations, which can be related to formation of intra- or interchain linkages.

Ideal‐filter capillary electrophoresis: A highly efficient partitioning method for selection of protein binders from oligonucleotide libraries

Selection of affinity ligands for protein targets from oligonucleotide libraries currently involves multiple rounds of alternating steps of partitioning of protein-bound oligonucleotides (binders) from protein-unbound oligonucleotides (nonbinders). We have recently introduced ideal-filter capillary electrophoresis (IFCE) for binder selection in a single step of partitioning. In IFCE, protein-binder complexes and nonbinders move inside the capillary in the opposite directions, and the efficiency of their partitioning reaches 109 , i.e., only one of a billion molecules of nonbinders leaks through IFCE while all binders pass through. The condition of IFCE can be satisfied when the magnitude of the mobility of EOF is smaller than that of the protein-binder complexes and larger than that of nonbinders. The efficiency of partitioning in IFCE is 10 million times higher than those of solid-phase-based methods of partitioning typically used in selection of affinity ligands for protein targets from oligonucleotide libraries. Here, we provide additional details on our justification for IFCE development. We elaborate on electrophoretic aspects of the method and define the theoretical range of EOF mobilities that support IFCE. Based on these theoretical results, we identify an experimental range of background electrolyte's ionic strength that supports IFCE. We also extend our interpretation of the results and discuss in-depth IFCE's prospective in practical applications and fundamental studies.

The Electrolytic Ionic Strength Effect on Corrosion Resistance and Crystallinity of Plasma Electrolytic Oxidation (PEO) Coating Developed on Ti6Al4V

The aim of this paper was to investigate the formation of an amorphous phase in the coating structure due to reduction in porosity and improvement in corrosion resistance of Ti6Al4V alloy during PEO process. The effect of crystallization on the electrochemical corrosion behavior and surface property of Ti6Al4V coating fabricated by plasma electrolytic oxidation (PEO) technique, was investigated in 5 wt %HCl solution. The coating compositions and electrochemical behaviors were examined by X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS) and polarization tests. The results showed that an increase in the ionic strength of electrolyte had a direct effect on the crystal size, the lattice strain and corrosion resistance. An increase in lattice strain due to Ti–O–Si led to a reduction in coating adhesion and corrosion resistance. A significant effect in phase transformation for Titania in the PEO process was not only led to an increase in polarization resistance but also reduced the number and size of porosity.

Dynamic viscosity of colloidal silica suspensions at low and high volume fractions

A comprehensive study was carried out on the dynamic viscosity of X30 silica dispersions at both high and low volume fractions of colloidal silica particles at various electrolyte ionic strength and pH values. Booth and Ruiz-Reina and Carrique theoretical models (R-R&C) were compared in predicting the primary electroviscous effect (PEE) for viscosity at low volume fractions. To this respect the colloidal dispersion was well characterised with regards to electrolyte properties such as the Debye length, κ−1, calculated from the ionic strength, and zeta potential, ζ, calculated from the electrophoretic mobility using the full numerical model by O’Brien and White (O’B&W). R-R&C hard sphere model (which is a modified version of Simha hard sphere model that includes a boundary condition by Happel on the outer radius of the cell) and the semi-empirical Krieger-Dougherty (K-D) models were fitted to the experimental data at high volume fractions. At both low and high volume fractions the viscosity increased with pH and decreased with ionic strength. At low volume fractions both theoretical models significantly underestimated the experimental dynamic viscosities obtained in this work. This could be attributed to the fuzzy structures for silica particles in aqueous conditions reported previously in the literature, where a significantly larger electroviscous parameter, p, was obtained experimentally for silica particles. The experimental electroviscous parameter, pexp, in this work was found to be roughly an order of magnitude up to 26 times larger than that predicted by Booth and around 5 ± 1 times larger than the predicted p by R-R&C model allowing the introduction of a correction factor in the PEE coefficient obtained from R-R&C model enabling good prediction for X30 silica dispersions by the latter model. The significant improvement of the electroviscous effect predictions by R-R&C model compared to Booth model may be attributed to the limitations invalidating the Booth model at the electrolyte conditions in this study. At high volume fractions, the R-R&C hard sphere cell model, gave a much better fit to the experimental data compared to the K-D model, which also had the advantage of being only dependent on a coefficient that linearly relates an effective volume fraction postulated for the fuzzy silica particles to the experimental. The K-D model however, depends on the intrinsic viscosity, [η], which requires the calculation of the experimental slope of the dynamic viscosity against volume fraction in the dilute limit, and also on a maximum packing fraction as a fitting parameter. Due to the effect of the fuzzy structures on the viscosity, the latter effective volume fraction ϕeff was calculated using two approaches: (i) as a fitting parameter by fitting the R-R&C hard sphere model to the experimental viscosity data over the entire volume fraction range, and (ii) by fitting only the linear part of the experimental viscosity at low volume fractions, It is concluded that the R-R&C hard sphere model with the effective volume fraction accounting for the fuzzy structures fits reasonably well the full range of experimental results at low and high volume fractions. When the model was used with the Adamczyk effective volume fraction (i.e., considering only the dilute region in the fitting procedure), the predictions became worse at high volume fractions where significant deviations from the experimental results were found upon the increase of pH.

Combined Ion Conductance and Atomic Force Microscope for Fast Simultaneous Topographical and Surface Charge Imaging.

We report here an advanced approach for simultaneous and independent submicroscale imaging of local surface charge and topography using microchanneled cantilevers, also known as FluidFM nanopipette probes. These hollow cantilevers with a 300 nm opening are employed for ion current measurements that provide access to the local properties of the electrical double layer using the phenomenon of ion current rectification, while also taking advantage of the force sensing capabilities for accurate probe vertical positioning and topography imaging. The independent nature of this atomic force microscope (AFM) feedback opens up a possibility to significantly increase the sensitivity for probing local surface charges in a wider range of salt concentrations, especially in electrolytes of low ionic strength (below 10 mM), where classical local ion conductance measurements with glass nanopipettes would suffer from inaccuracies and instabilities, but where the electrical double layer extends further into the liquid medium and has stronger effect on the measured ion currents for charge imaging. We demonstrate that the measurements with FluidFM do not compromise the positioning accuracy and enable accurate and simultaneous topographical and charge imaging in contact mode (similar to AFM) at high scanning rates, approaching thousands of pixels per second, therefore overtaking state-of-the-art techniques for charge mapping by at least 2 orders of magnitude (the probes reach translation rates of 120 μm s-1 equating to 2 ms per image pixel). We also reveal experimentally the physical limit of this high speed scanning, constrained by the rate of ion redistribution in surface-induced rectification required for double layer sensing and charge mapping.

The influence of pulp and interfacial chemistry and mode of electrical power input on electroosmotic dewatering of Na-exchanged smectite dispersions

Abstract In this study, pulp and interfacial chemistry, gravity settling/drainage and electroosmotic (EO) dewatering behaviour of two types of fine, Na-exchanged smectite clay (high and low Na content montmorillonites) slurries were investigated as a function of background electrolyte ionic strength and time at pH 7.5 with constant voltage (0.5 vs. 1 V/cm initial field strength) or current density (12.5 vs. 25 A/m2). The two smectite variants displayed significantly different mineral chemistry and particle zeta potential, the latter dependent on Ca(II) background. Suppressed swelling and marked reduction in zeta potential magnitude occurred at 0.03–0.3 M Ca(II) ionic strength, the extent of which was greater for low than high Na-smectite pulps. Ca(II) ionic strength of ~0.1 M improved pre-EO gravity dewatering from

Electrodeposition of rhenium with suppressed hydrogen evolution from water-in-salt electrolyte

The electrodeposition of rhenium was studied using a “water-in-salt” type of electrolyte with a superhigh concentration of lithium chloride to suppress the proton activity. Cyclic voltammetry and DC plating were carried out on rotating disc electrodes to characterize the electrolyte and to prepare thin films. Electrolytes without metal cations were also studied, where the cathodic reduction of proton was significantly suppressed when the concentration of supporting salt approached the solubility limit. Film cracks were eliminated for rhenium films deposited from this superhigh ionic strength electrolyte.

Influence of Feed-Electrode Concentration Differences in Flow-Electrode Systems for Capacitive Deionization

The common performance metrics ascribed to flow electrode capacitive deionization systems can vary significantly depending on the mode of operation and initial system conditions. Through varying the flow electrolyte ionic strength, performance values such as average salt adsorption rate and energy consumption can vary by as much as 51 and 55%. This variability from cycle to cycle is in part due to changes in the electrical conductivity (ohmic) but is also due to the introduction of competing transport processes. Diffusive transport can enhance or diminish the rate of desalination and energy recovery, creating a larger degree of error in reported values. Here, we propose a dimensionless ratio comparing diffusion and electromigration-based transport to measure performance stability. Unstable system performance is most prominent when the feed ionic strength does not match the flow electrode ionic strength. In this scenario, the ratio of the diffusion to electromigration transport reached a maximum. Conversel...

Cyclic band compression in toroidal capillary electrophoresis delivers an unlimited number of theoretical plates with a quadratic growth in time and a constant peak capacity.

Analytical instruments able to provide extremely high sensitivities, separation efficiencies, and peak capacities are important for both applied sciences and basic research. It is even more interesting if this can be achieved within organic, aqueous, and physiological solutions without restricting the operation parameters, such as buffer pH, temperature, ionic strength, and background electrolyte composition. Toroidal capillary electrophoresis offers this potential, as was recently proposed and demonstrated. In this platform, the analytes perform continuous round trips inside a fused-silica capillary having a torus-like shape. In the present work, the equations of the number of plates and peak capacity are deduced when on-column cyclic thermal band compression is applied. They are expressed as a function of the number of turns performed by the analyte, axial length of the toroid, number of microholes (reservoirs), compression factor, number of compression events performed per turn, and applied voltage. It was found that the variances of the bands reach a steady state, regardless of the number of dispersion mechanisms present. Consequently, the number of theoretical plates grows indefinitely as the square of time. The expression of peak capacity shows a well-defined limiting value that remains constant over time.

Hidden Features: Characterizing Carbon Electrodes in Low Ionic Strength Electrolytes for Capacitive Desalination Applications

Capacitive desalination (CDI) is a promising technology for reducing the salinity of brackish water streams. CDI typically employs a nanoporous carbon supercapacitor architecture with the added ability to flow electrolyte through the cell for deionization. Unlike supercapacitors, though, CDI operates with low ionic-strength liquids (e.g., 20 mM NaCl). Characterization in these electrolytes unveils important features in the CV and EIS data that are not commonly observed in supercapacitor studies. Examples of such features are the emergence of a strong “charge-transfer” resistance at mid-to-high frequencies in the EIS spectrum, local minima in the CV curves that are related to a point of zero charge, and potential artifacts due to ion depletion. These features ultimately underlie the system capacitance, device resistance, and effective operational voltage window, which are all strongly related to desalination performance. Here we examine these features in flow-through electrode CDI devices (fteCDI) with activated hierarchical carbon aerogel monoliths (HCAMs) derived from carbonized and activated resorcinol-formaldehyde aerogel. Work at LLNL was performed under the auspices of the US DOE by LLNL under Contract DE-AC52-07NA27344.

Electroanalytical determination of eugenol in clove oil by voltammetry of immobilized microdroplets

The determination of eugenol employing voltammetry of immobilized microdroplets (VIM) is reported in this work. The construction of the electrode was based on a glassy carbon substrate modified with carbon black nanoparticles and eugenol standard or clove oil sample within a dihexadecyl hydrogen phosphate (DHP) film. The different experimental parameters related to this proposed procedure, i.e., supporting electrolyte composition, pH, ionic strength, and square-wave voltammetry (SWV) parameters (amplitude, frequency, and step potential) were optimized. By doing that, the SWV measurements were performed on the following optimum experimental conditions: 0.2 mol L−1 phosphate buffer solution (pH 2.0), amplitude 90 mV, frequency 30 Hz, and step potential 5 mV. The analytical curve for eugenol was linear in the wide range from 0.03 to 26 μg (r = 0.999) with limits of detection (LOD) and quantification (LOQ) of 0.13 and 0.42 ng, respectively. Three commercial clove oil samples were successfully immobilized and analyzed using the proposed VIM procedure showing eugenol concentrations ranging from 14.0 to 68.3%. Comparing the results obtained by the proposed and comparative procedure (spectrophotometric), relative standard deviations (RSDs) lower than 5.0% were verified, demonstrating the concordance of the results obtained by both methods.

If Squeezed, a Camel Passes Through the Eye of a Needle: Voltage-Mediated Stretching of Dendrimers Facilitates Passage Through a Nanopore.

Herein, we report uni-molecular observations of electric potential- and electrolyte-dependent elasticity of poly(amidoamine) (PAMAM)-G1.5 dendrimers containing sodium carboxylate surface groups, using the electric field-assisted migration through the α-hemolysin nanopore (α-HL). Although at moderate transmembrane potentials the dendrimer (~ 2.5nm in diameter) is sterically excluded from translocation across the constriction region of the nanopore (~ 1.5nm in diameter), we found a threshold for its translocation that depends on both the electrolyte pH and ionic strength. We posit that the decreased repulsive intramolecular interactions among dendrimer's branches at low when compared to neutral pH, caused mainly by the protonation of surface groups on the dendrimer, determine a larger propensity of the dendrimer to collapse and deform. This in turns enables the dendrimer to adopt more favorably conformations that facilitate its optimal squeezing through the α-HL's constriction region at low pH, despite the fact that the estimated net force acting on it becomes approximately one order of magnitude lower than at neutral pH. Experiments performed in a low ionic strength buffer, which decreases Coulombic screening, enhance the intramolecular forces on the dendrimer and renders the dendrimer stiffer than in high ionic strength buffer, confirming the dendrimer elastic properties-dependent threshold for deformation inside the nanopore.

A precision structured smart hydrogel for sensing applications

We report on a macroinitiator based smart hydrogel film applied on a microcantilever for sensing applications. The studied hydrogel features a comparatively wide dynamic range for changes in the electrolyte's ionic strength. Furthermore, it offers a simple spin coating process for thin film deposition as well as the capability to obtain high aspect ratio microstructures by reactive ion etching. This makes the hydrogel compatible to microelectromechanical system integration. As a proof of concept, we study the response of hydrogel functionalized cantilevers in aqueous sodium chloride solutions of varying ionic strength. In contrast to the majority of hydrogel materials reported in the literature, we found that our hydrogel still responds in high ionic strength environments. This may be of future interest for sensing e.g., in sea water or physiological environments like urine.