Christian Chamberlayne - Academia.edu (original) (raw)

Papers by Christian Chamberlayne

RSC Advances

Controlled release using electroresponsive nanoparticles and an ultrasonically powered battery-fr... more Controlled release using electroresponsive nanoparticles and an ultrasonically powered battery-free implant demonstrate a potential implantable drug delivery system platform.

Journal of Physical Chemistry B, Oct 4, 2022

Journal of Physical Chemistry Letters, Sep 11, 2020

Many common experimental systems have electric double layers containing weak electrolytes, includ... more Many common experimental systems have electric double layers containing weak electrolytes, including systems with buffers. The pH at the boundary of the diffuse layer is an important parameter for determining the physicochemical state of the system, including surface charge density. We show that the Boltzmann equilibrium relation can be used as an exact solution for weak electrolyte electric double layers. Using these results, we provide a closed-form relation for the maximum pH change in a buffered electric double layer, in terms of the boundary potential. Importantly, our results suggest that equilibrium electric double layer concepts developed for strong electrolytes can be expanded to include weak electrolytes.

Journal of Chemical Physics, Feb 7, 2022

A water microdroplet in air or oil typically possesses an electric double layer (EDL) from prefer... more A water microdroplet in air or oil typically possesses an electric double layer (EDL) from preferential adsorption of surface-bound ions at the periphery. We present calculations of the ion gradients within a microdroplet at equilibrium, including systems containing buffers and water autoionization. These ion gradients are used to calculate the potential energy stored within the microdroplet. We consider how this stored potential energy can be utilized to drive chemical reactions, much like an electrochemical cell. Effective voltages as high as 111 mV are found for microdroplets having a low surface charge density (0.01 ions per nm 2). Two sources of potential energy are investigated: (1) the electrostatic energy of the microdroplet's EDL; and (2) shifts in other chemical equilibria coupled to the main reaction through the EDL. A particularly important example of the latter is water autoionization, wherein the reaction of interest causes a flattening of the [H + ] gradient within the EDL, resulting in a net recombination of H + and OHthroughout the microdroplet. Numerical calculations are performed using a continuum model consisting of a balance between electromigration and diffusion of ions throughout the microdroplet. Our treatment accounts for the autoionization of water and any chemical equilibrium of buffers present. Results are presented for uncharged water microdroplets with low amounts of salts and simple buffers in them. However, the calculational method presented here can be applied to microdroplets of any net charge, composed of any solvent, containing ions of any valence, and containing complex mixtures of chemical equilibria.

PubMed, Oct 1, 2020

Small water microdroplets in microfluidic systems have a high surface charge density resulting fr... more Small water microdroplets in microfluidic systems have a high surface charge density resulting from charged surfactants. As a result, an electric double layer forms inside the droplet. Depletion of ions from the center of the droplet to form the double layer can shift the concentration of ions dramatically from that of the microdroplet precursor solution. Here we show numerical solutions to the Gouy-Chapman model in spherical coordinates. Some notable effects include: 1) large percentages of the microdroplet volume experience very large DC electric fields; 2) many ions get forced into a Stern layer giving dramatically different conditions from the bulk.

QRB discovery, 2021

Mist is generated by ultrasonic cavitation of water (Fisher Biograde, pH 5.5-6.5) at room tempera... more Mist is generated by ultrasonic cavitation of water (Fisher Biograde, pH 5.5-6.5) at room temperature (20-25°C) in open air with nearly constant temperature (22-25°C) but varying relative humidity (RH; 24-52%) over the course of many months. Water droplets in the mist are initially about 7 μm in diameter at about 50% RH. They are collected, and the concentration of hydrogen peroxide (H 2 O 2) is measured using commercial peroxide test strips and by bromothymol blue oxidation. The quantification method is based on the Fenton chemistry of dye degradation to determine the oxidation capacity of water samples that have been treated by ultrasonication. It is found that the hydrogen peroxide concentration varies nearly linearly with RH over the range studied, reaching a low of 2 parts per million (ppm) at 24% RH and a high of 6 ppm at 52% RH. Some possible public health implications concerning the transmission of respiratory viral infections are suggested for this threefold change in H 2 O 2 concentration with RH.

Chemical Communications, 2016

Nanoscale, 2018

Drug delivery systems (DDS) that allow spatially and temporally controlled release of drugs are o... more Drug delivery systems (DDS) that allow spatially and temporally controlled release of drugs are of particular interest in the field of drug delivery. These systems create opportunities for individually tailored doses of drugs to be administered as well as reduce side effects by localizing the initial drug dose to the organ of interest. We present an electroresponsive DDS in the form of a bioresorbable nanocomposite film which operates at low voltages (<−2 V). The method is based on electrochemically generating local pH changes at an electrode surface to induce dissolution of a pH-sensitive polymer, which is used as the carrier material. We previously demonstrated this proof-of-concept using a poly(methyl methacrylate-co-methacrylic acid) (co-PMMA) copolymer commercially marketed as Eudragit S100 (EGT). However, as EGT is soluble at a pH above 7, experiments were performed in isotonic saline solutions (pH ~6.4). In this work, we have synthesized co-PMMA with a variety of monomer ratios to shift the solubility of the copolymer to higher pH values, and developed a polymer that can be used under physiologically relevant conditions. The generalizability of this system was demonstrated by showing controlled release of different drug molecules with varying parameters like size, hydrophobicity, and pK a. Fluorescein, a hydrophilic model compound, meloxicam, a hydrophobic anti-arthritic medication, curcumin, a small molecule with anti-cancer therapeutic potential, and insulin, a polypeptide hormone used in the treatment of hypoglycemia, could all be released on demand with minimal leakage. The drug loading achieved was ~32 wt% by weight of the co-polymer.

Journal of Chemical Physics, May 14, 2020

It is well established that the chemistry in microdroplets has been found to be radically differe... more It is well established that the chemistry in microdroplets has been found to be radically different from reactions in bulk, particularly in the case of water. It has also been established that there is a threshold size for microdroplets to behave differently than droplets near the 10 µm diameter range. We present a three-dimensional electrostatic treatment in the spirit of the Gouy–Chapman model for double layers at interfaces. Our treatment predicts a strong concentration of charged molecules toward the surface of the droplet. As the droplet size deceases, the majority of the volume of the liquid experiences a large DC electric field. Such electric fields are highly unusual in a conducting fluid such as water. We believe that this unique environment helps to explain the reaction rate acceleration and new chemistry that have been observed in microdroplets compared to bulk phase.

We have proposed and demonstrated a robust coherent optical technique, the "Stark induced adiabat... more We have proposed and demonstrated a robust coherent optical technique, the "Stark induced adiabatic Raman passage" or SARP for preparing single vibrational energy eigenstate of a molecule. Using SARP we have, for the first time, demonstrated population inversion between a ground vibrational (v=0, J) and an excited (v > 0, J') vibrational level of H2 within the ground X 1?g+ electronic state. In addition, we have prepared a coherent superposition of degenerate M-states belonging to a single rovibrational (v=1, J=2) energy eigenstate within the ground X 1?g+ electronic state of H2. The phase entangled superposition states opened new avenues to coherently

Topics in Catalysis, Mar 23, 2021

Redox reactions have been observed when an electrostatically charged insulator is placed in conta... more Redox reactions have been observed when an electrostatically charged insulator is placed in contact with a solution, and this phenomenon is referred to as single-electrode electrochemistry. In this study we explore how important is the chemical reactivity of the charge carriers on the surface compared to the voltage caused by the density of charges on the surface which set up an electric double layer. We address complications arising from the surface potential’s dependence upon the electrolyte concentration caused by the fixed surface charge density of the electrode. We present an analytical solution for the effective potential in single-electrode electrochemistry at a planar surface and show that it is not the same as the potential at the insulating surface. We reach two major conclusions: (1) the voltage applied to the reaction from discharging the electrode approaches a limiting value, and (2) the majority of single-electrode reactions are caused primarily by the chemical reactivity of the charge carrier on the electrode surface and not from discharging the static charge on the electrode.

RSC Advances, 2013

The thiol-ene photopolymerization of resorcinarene cavitand thiol with various alkene building bl... more The thiol-ene photopolymerization of resorcinarene cavitand thiol with various alkene building blocks led to the formation of hollow nanocapsules of varying thickness and rigidity, depending on the valency of the alkenes.

The Journal of Physical Chemistry B

Analytical Chemistry, 2022

Sonic spray creates a stream of neutral and charged microdroplets without application of voltage,... more Sonic spray creates a stream of neutral and charged microdroplets without application of voltage, heating, laser irradiation, or corona discharge. The solvent of interest flows through an inner capillary (usually constructed of fused silica) that is surrounded by an outer stainless-steel tube through which a nebulizing gas flows under pressure. This technique has been widely used as the interface in mass spectrometric studies for chemical analysis and for understanding microdroplet chemistry. We have used light scattering to characterize the size distribution and density for water microdroplets as a function of several parameters, such as water quality, water flow rate, nebulizing gas pressure, and sonic sprayer geometry. We find that the size distribution of the microdroplets, which is critical to many applications, depends most sensitively on the distance between the inner and outer capillary outlets and the gas flow pressure. The best performance as measured by the smallness of the microdroplet diameters is obtained when the gas flow pressure is the highest and there is no separation distance, d, between the two capillary outlets. In addition, at d = 0 mm, the microdroplet diameter distribution is nearly independent of the water flow rate, indicating that studies under these conditions can be scaled up.

The Journal of Chemical Physics, 2022

A water microdroplet in air or oil typically possesses an electric double layer (EDL) from the pr... more A water microdroplet in air or oil typically possesses an electric double layer (EDL) from the preferential adsorption of surface-bound ions at the periphery. We present the calculations of the ion gradients within a microdroplet at equilibrium, including systems containing buffers and water autoionization. These ion gradients are used to calculate the potential energy stored within the microdroplet. We consider how this stored potential energy can be utilized to drive chemical reactions, much like an electrochemical cell. Effective voltages as high as 111 mV are found for microdroplets having a low surface charge density (0.01 ions per nm2). Two sources of potential energy are investigated: (1) the electrostatic energy of the EDL of the microdroplet and (2) shifts in other chemical equilibria coupled to the main reaction through the EDL. A particularly important example of the latter is water autoionization, wherein the reaction of interest causes a flattening of the [H+] gradient ...

2021 IEEE Biomedical Circuits and Systems Conference (BioCAS), 2021

Implantable drug delivery systems can enable targeted, personalized, and on-demand treatments whi... more Implantable drug delivery systems can enable targeted, personalized, and on-demand treatments while minimizing the risk of side effects. In this work, we present an ultrasonically powered implantable potentiostat with bidirectional communication for programmable electrochemically controlled drug delivery. The system consists of piezoelectric transducers for wireless power and data, a 180 nm CMOS integrated circuit, and a custom drug delivery module containing drug-loaded electroresponsive nanoparticles. The chip includes power and downlink data recovery circuits for simultaneous power and data transfer up to 50 kbps, a programmable wide-range potentiostat capable of providing potentials up to ±1.5 V and sensing current up to ±100 µA, and a 125 kbps data transmitter. Wirelessly powered and controlled fluorescein release is used to demonstrate the drug delivery system.

Micro total analysis systems : proceedings of the ... [Mu] TAS International Conference on Miniaturized Chemical and Biochemical Analysis Systems. [Mu] TAS, 2020