Shideh Kabiri Ameri

All electronic approach for high-throughput cell trapping and lysis with electrical impedance monitoring

We present a portable lab-on-chip device for high-throughput trapping and lysis of single cells with in-situ impedance monitoring in an all-electronic approach. The lab-on-chip device consists of microwell arrays between transparent conducting electrodes within a microfluidic channel to deliver and extract cells using alternating current (AC) dielectrophoresis. Cells are lysed with high efficiency using direct current (DC) electric fields between the electrodes. Results are presented for trapping and lysis of human red blood cells. Impedance spectroscopy is used to estimate the percentage of filled wells with cells and to monitor lysis. The results show impedance between electrodes decreases with increase in the percentage of filled wells with cells and drops to a minimum after lysis. Impedance monitoring provides a reasonably accurate measurement of cell trapping and lysis. Utilizing an all-electronic approach eliminates the need for bulky optical components and cameras for monitoring.

Flexible pH-Sensing Hydrogel Fibers for Epidermal Applications

Epidermal pH is an indication of the skins physiological condition. For example, pH of wound can be correlated to angiogenesis, protease activity, bacterial infection, etc. Chronic nonhealing wounds are known to have an elevated alkaline environment, while healing process occurs more readily in an acidic environment. Thus, dermal patches capable of continuous pH measurement can be used as point-of-care systems for monitoring skin disorder and the wound healing process. Here, pH-responsive hydrogel fibers are presented that can be used for long-term monitoring of epidermal wound condition. pH-responsive dyes are loaded into mesoporous microparticles and incorporated into hydrogel fibers using a microfluidic spinning system. The fabricated pH-responsive microfibers are flexible and can create conformal contact with skin. The response of pH-sensitive fibers with different compositions and thicknesses are characterized. The suggested technique is scalable and can be used to fabricate hydrogel-based wound dressings with clinically relevant dimensions. Images of the pH-sensing fibers during real-time pH measurement can be captured with a smart phone camera for convenient readout on-site. Through image processing, a quantitative pH map of the hydrogel fibers and the underlying tissue can be extracted. The developed skin dressing can act as a point-of-care device for monitoring the wound healing process.

Three dimensional graphene scaffold for cardiac tissue engineering and in-situ electrical recording

In this paper, we present a three-dimensional graphene foam made of few layers of CVD grown graphene as a scaffold for growing cardiac cells and recording their electrical activity. Our results show that graphene foam not only provides an excellent extra-cellular matrix (ECM) for the culture of such electrogenic cells but also enables recording of its extracellular electrical activity in-situ. Recording is possible due to graphenes excellent conductivity. In this paper, we present our results on the fabrication of the graphene scaffold and initial studies on the culture of cardiac cell lines such as HL-1 and recording of their real-time electrical activity.

A Flexible Gastric Gas Sensor Based on Functionalized Optical Fiber

We present a gastric gas sensor based on conjoined dual optical fibers functionalized with sensitive optical dyes for sensing gases in both fluidic and gaseous environments. The sensor aims to sense various concentrations of carbon dioxide (CO2) and ammonia (NH3), which are two significant biomarkers of H. pylori infection in the stomach. It is known that CO2 and NH3 are released during the hydrolysis of urea by H. pylori, a bacterium that may cause stomach cancer with relatively high probability. CO2 and NH3 sensitive optical dyes, cresol red ion pair and zinc tetraphenylporphyrin, are embedded in silica beads and then functionalized onto the thin PDMS-coated fiber tip. Each type of dye provides a unique spectral emission response when excited with light ranging from 450 to 700 nm. Two SMA connector legs of the as-functionalized sensor are connected to an external light source for illumination and a ultraviolet-visible-near infrared (UV-Vis-NIR) spectrometer for signal collection/readout. To perform the measurements, one fiber illuminates while the other fiber collects the back-scattered light and feeds it to the UV-Vis-NIR spectrometer to measure the change in light spectrum as a function of CO2 or NH3 concentration. This method is easy and flexible and achieves ppm level sensitivity to targeted gas analytes. The proposed sensor can be integrated into a customized tethered capsule for adjunctive diagnosis of H. pylori infection to improve the accuracy of visual endoscopic inspection.

Three dimensional monolayer graphene foam for ultra-sensitive pH sensing

In this work, we present liquid gated three-dimensional graphene transistor for pH sensing. The sensor is made of three-dimensional network of graphene coated with hafnium oxide (HfO2) operating as a pH-sensitive liquid gated field effect transistor with super-nerstian sensitivity. We attribute high sensitivity in this device to the coating of HfO2 which provides increased interaction with hydrogen ions in the solution and on the three dimensional foam-like structure of the graphene transistor which provides very high surface-to-volume ratio.

Disposable colorimetric geometric barcode sensor for food quality monitoring

In this work, we present a disposable paper-based optical sensor arranged as barcode for monitoring food spoilage. The color-changing barcode is embedded in the food packaging and monitored using smart phone. The color change of different optical sensing dyes that make up the barcode is due to the emission of volatile organic compounds (VOCs) from food. Different geometric shapes are assigned to each sensing dye for identification. The sensor fabrication is low-tech and easy to perform. A smart phone quantifies the color change in the barcode food sensor, which provides a non-contact metric of food freshness/spoilage.

pH-Sensing Hydrogel Fibers: Flexible pH-Sensing Hydrogel Fibers for Epidermal Applications (Adv. Healthcare Mater. 6/2016)

On page 711 S. Sonkusale, A. Khademhosseini, and co-workers present pH-responsive hydrogel fibers that can be used for long-term monitoring of epidermal wound conditions. pH-responsive dyes are loaded into mesoporous microparticles, which are then embedded into hydrogel fibers developed through microfluidic spinning. The fabricated pH-responsive microfibers are flexible and can create conformal contact with skin. Images of the pH-sensing fibers during real-time pH measurement can be captured with a smart phone camera for convenient readout on-site.

Microfluidic optoelectronic sensor array for detection of dissolved CO 2 based on halocromic dye-doped polymeric microbeads

We present a microfluidic optoelectronic sensor for detection of dissolved CO2 in aqueous samples. The sensor contains an array of wells embedded in a microfluidic device and filled with ion-exchange polymeric microbeads doped with halocromic dyes. We have developed a simple procedure for microbeads deposition that allows incorporation of virtually any combination of halocromic dyes, providing a route for cross-reactive sensing. Due to a versatile optical arrangement, using LEDs and photodiodes, optical signals are easily translated into electronic readouts. We demonstrate the sensor ability to provide distinct responses to different concentrations of dissolved CO2. Moreover, the sensor shows no cross sensitivity to acidity not related to dissolved CO2.