Uday Tata

Exploiting a patch antenna for strain measurements

The feasibility of applying patch antennas for strain measurement is investigated. The resonance frequency of a patch antenna is determined by the size of its metallic patch. An applied strain changes the dimensions of the metallic patch, resulting in a shift in the antenna resonant frequency. Therefore, the applied strains can be measured from the changes in antenna resonant frequency. A dual-frequency patch antenna was designed and fabricated using conventional photolithography techniques. The application of the patch antenna for strain measurement was evaluated by bonding the patch antenna to an aluminum cantilever beam and applying loads at the free end of the cantilever beam. The shifts of the return loss S11 curves under loads were correlated to the strains experienced by the patch antenna. The strain sensitivity of the antenna obtained from experimental measurements agreed well with the analytical prediction.

An Implantable, Batteryless, and Wireless Capsule With Integrated Impedance and pH Sensors for Gastroesophageal Reflux Monitoring

In this study, a device for gastroesophageal reflux disease (GERD) monitoring has been prototyped. The system consists of an implantable, batteryless and wireless transponder with integrated impedance and pH sensors; and a wearable, external reader that wirelessly powers up the transponder and interprets the transponded radio-frequency signals. The transponder implant with the total size of 0.4 cm ×0.8 cm ×3.8 cm harvests radio frequency energy to operate dual-sensor and load-modulation circuitry. The external reader can store the data in a memory card and/or send it to a base station wirelessly, which is optional in the case of multiple-patient monitoring in a hospital or conducting large-scale freely behaving animal experiments. Tests were carried out to verify the signal transduction reliability in different situations for antenna locations and orientation. In vitro, experiments were conducted in a mannequin model by positioning the sensor capsule inside the wall of a tube mimicking the esophagus. Different liquids with known pH values were flushed through the tube creating reflux episodes and wireless signals were recorded. Live pigs under anesthesia were used for the animal models with the transponder implant attached on the esophageal wall. The reflux episodes were created while the sensor data were recorded wirelessly. The data were compared with those recorded independently by a clinically used wireless pH sensor capsule placed next to our implant transponder. The results showed that our transponder detected every episode in both acid and non-acid nature, while the commercial pH sensor missed events that had similar, repeated pH values, and failed to detect pH values higher than 10. Our batteryless transponder does not require a battery thus allowing longer diagnosis and prognosis periods to monitor drug efficacy, as well as providing accurate assessment of GERD symptoms.

Simulation, implementation, and analysis of an optical fiber bundle distance sensor with single mode illumination

A simulation model for an optical fiber bundle distance sensor with a single mode fiber as the illumination fiber and a multimode fiber as the receiving fiber is presented. Approximating the illumination light exiting the single mode fiber as having a Gaussian intensity profile, a closed-form solution of the reflected light coupled into the receiving fiber was derived. A distance sensor was implemented and the measured sensor outputs were compared with the simulation data to verify the theoretical model. The performance of the distance sensor with different design parameters was analyzed. Design guidelines for achieving desired sensor performances are suggested.

Sol-Gel Iridium Oxide-Based pH Sensor Array on Flexible Polyimide Substrate

Iridium oxide pH sensing film is demonstrated with wide pH-sensing ranges, high durability, and small drifts in potentials. Using sol-gel process, a lower fabrication cost and less labor-intensive method, to deposit iridium oxide thin films for pH sensing is reported previously by our group with expected advantages. In this paper, we fabricate and test pH sensing characteristics of 4 × 4 anhydrous iridium oxide thin-film electrode arrays on flexible substrates. The sensors in arrays exhibit Nernstian potential responses in the range of 57.0-63.4 mV/pH. Stability, repeatability, and hysteresis effects of the pH sensor arrays are examined. A multichannel recording system is built to demonstrate the functionality of the pH sensor arrays in monitoring spatial and temporal pH changes across a surface.

Flexible Sputter-Deposited Carbon Strain Sensor

In this letter, we report a piezoresistive amorphous carbon strain sensor fabricated on a flexible polyimide substrate. Amorphous carbon was sputter-deposited onto a 125-μm-thick polyimide film and the strain gauges were tailored using laser micromachining. The strain sensors were tested by using a cantilever setup to obtain sensitivity, hysteresis, repeatability, and dynamic response. Gauge factors in the range of 6-9 have been achieved.

The Migration of Cancer Cells in Gradually Varying Chemical Gradients and Mechanical Constraints

We report a novel approach to study cell migration under physical stresses by utilizing established growth factor chemotaxis. This was achieved by studying cell migration in response to epidermal growth factor (EGF) chemoattraction in a gradually tapered space, imposing mechanical stresses. The device consisted of two 5-mm-diameter chambers connected by ten 600 µm-long and 10 µm-high tapered microchannels. The taper region gradually changes the width of the channel. The channels tapered from 20 µm to 5 µm over a transition length of 50 µm at a distance of 250 µm from one of the chambers. The chemoattractant drove cell migration into the narrow confines of the tapered channels, while the mechanical gradient clearly altered the migration of cells. Cells traversing the channels from the wider to narrow-end and vice versa were observed using time-lapsed imaging. Our results indicated that the impact of physical stress on cell migration patterns may be cell type specific.

Evaluation of Cytotoxic Effects of Different Concentrations of Porous Hollow Au Nanoparticles (PHAuNPs) on Cells

Nanoparticles (NPs) have been introduced as a suitable alternative in many in vivo bioapplications. The risks of utilizing nanoparticles continue to be an ongoing research. Furthermore, the various chemicals used in their synthesis influence the cytotoxic effects of nanoparticles. We have investigated the cytotoxicity of Porous Hollow Au Nanoparticles (PHAuNPs) on cancer cell lines PC-3, PC-3ML, and MDA-MB-231 and the normal cell line PNT1A. Cell proliferation for the different cells in the presence of different concentrations of the PHAuNPs was assessed after 24 hours and 72 hours of incubation using MTT assay. The study also included the cytotoxic evaluation of pegylated PHAuNPs. Identical cell seeding densities, particle concentrations, and incubation times were employed for these two types of Au nanoparticles. Our results indicated that (1) impact on cell proliferation was concentration dependent and was different for the different cell types without cellular necrosis and (b) cellular proliferation might be impacted more based on the cell line.

A Novel Multiwell Device to Study Vascular Smooth Muscle Cell Responses Under Cyclic Strain

Vascular smooth muscle cells (VSMCs) are constantly exposed to cyclic stretch in the body, which makes it beneficial to study the effects of cyclic stretch on VSMCs. In this study, we developed a poly(dimethyl siloxane) (PDMS) compact six-well device that can be used to study the combined effect of cyclic strain and various growth factors on cultured VSMCs. Cell adhesion, alignment, and proliferation under 10% or 20% cyclic strain at 1 Hz were studied using this surface-enhanced PDMS device. The combined effects of cyclic strain with either transforming growth factor-β, vascular endothelial growth factor, fibroblast growth factor, or epidermal growth factor on VSMC proliferation was also examined. Results showed that VSMCs adhered well on the surface-enhanced multiwell device and they aligned perpendicularly to the direction of the cyclic strain. Cell proliferation was inhibited by 10% cyclic strain at 1 Hz compared with static control. The mitogenic effects of the growth factor were less potent under either 10% or 20% cyclic strain. With simple modification to accommodate more wells, this device could potentially be a useful tool for more economical, high throughput screening application.

Study of lung-metastasized prostate cancer cell line chemotaxis to epidermal growth factor with a BIOMEMS device

Understanding the effects of different growth factors on cancer metastasis will enable researchers to develop effective post-surgery therapeutic strategies to stop the spread of cancer. Conventional Boyden chamber assays to evaluate cell motility in metastasis studies require high volumes of reagents and are impractical for high-throughput analysis. A microfluidic device was designed for arrayed assaying of prostate cancer cell migration towards different growth factors. The device was created with polydimethylsiloxane (PDMS) and featured two wells connected by 10 micro channels. One well was for cell seeding and the other well for specific growth factors. Each channel has a width of 20??m, a length of 1?mm and a depth of 10??m. The device was placed on a culture dish and primed with growth media. Lung-metastasized cells in suspension of RPMI 1640 media supplemented with 2% of fetal bovine serum (FBS) were seeded in the cell wells. Cell culture media with epidermal growth factor (EGF) of 25, 50, 75, 100 and 125?ng?ml?1 concentrations were individually added in the respective growth factor wells. A 5-day time-lapsed study of cell migration towards the chemoattractant was performed. The average numbers of cells per device in the microchannels were obtained for each attractant condition. The results indicated migration of cells increased from 50 to 100?ng?ml?1 of EGF and significantly decreased at 125?ng?ml?1 of EGF, as compared to control.

A Microfluidic Assay for Metastasis Potential Analysis

We have designed and characterized a poly-dimethyl-siloxane (PDMS) based microfluidic device called MiMiC™ that enables time-lapse study of cell migration. Cell migration is a key step of malignant metastasis during cancer progression. The device mimics the narrow confines the cells need to traverse and the microenvironments that are similar to the ones inside human body. Photolithography and soft lithography processes were used to fabricate the microfluidic devices. The device consists of two separate chambers connected by microfluidic channels allowing introduction of cells in one chamber and chemoattractants in the other. The response of lung-metastasized prostate cancer (PC-3-ML) cells and their migration response to chemoattractants were observed and analyzed. The numbers of cells under migration were determined from time-lapse images and compared to control groups. Our microfluidic assays provide advantages over the traditional Boyden chambers such as time-lapse observation, use of smaller amounts of reagents and direct assessment of cells under migration.Copyright