Sanchali Deb

A Passive Radio-Frequency pH-Sensing Tag for Wireless Food-Quality Monitoring

We present a new method, suitable for food quality management by wirelessly monitoring pH level changes in food with a flexible pH sensor embedded in a batteryless radio-frequency (RF) transponder. The wireless sensor tag includes a flexible pH sensor based on miniature iridium oxide (IrOx) and silver chloride (AgCl) sensing electrodes integrated on a deformable substrate, and batteryless wireless communication circuitry. The sensor tag and reader system is designed to achieve convenient, long-term, and on-demand wireless in situ monitoring of food quality, especially for large-quantity applications and continuous monitoring from place of production to retail stores. Low-cost IrOx sol-gel fabrication process was applied on polymeric substrates to form the flexible sensing films, and a sensitivity of -49.7 mV/pH was achieved. Inducting coupling provides electromagnetic energy from the reader to drive the transponder circuits that retransmit the sensor-data modulated signals back to the reader. The electrochemical potential created by the IrOx/AgCl sensing electrodes is converted to a modulated frequency and the system achieves a sensitivity of 633 Hz/pH. The wireless pH sensing system was tested for in situ monitoring of the spoilage processes in fish meats continuously for over 18 h. The feasibility of wirelessly monitoring pH values in fish meats that could be used to identify spoilage remotely has been demonstrated.

An endoscopic wireless gastrostimulator (with video)

BACKGROUND Gastric electric stimulation (GES) at a high-frequency, low-energy setting is an option for treating refractory gastroparesis. The currently available commercial stimulator, the Enterra neurostimulator (Medtronic Inc, Minneapolis, MN), however, requires surgical implantation and is powered by a nonrechargeable battery. OBJECTIVE To develop and test a miniature wireless GES device for endoscopic implantation in an experimental model. DESIGN In-vivo gastric signals were recorded and measured in a nonsurvival swine model (n = 2; 110-lb animals). INTERVENTION An endoscopically placed, wireless GES device was inserted into the stomach through an overtube; the two GES electrodes were endoscopically attached to the gastric mucosa and secured with endoclips to permit stimulation. MAIN OUTCOME MEASUREMENTS Stable electrogastrogram measures were observed during GES stimulation. RESULTS Electrogastrogram recordings demonstrated that gastric slow waves became more regular and of constant amplitudes when stomach tissues were stimulated, in comparison with no stimulation. The frequency-to-amplitude ratio also changed significantly with stimulation. LIMITATION Nonsurvival pig studies. CONCLUSION Gastric electric stimulation is feasible by our endoscopically implanted, wireless GES device.

Development of innovative techniques for the endoscopic implantation and securing of a novel, wireless, miniature gastrostimulator (with videos)

BACKGROUND Gastric stimulation via high-frequency, low-energy pulses can provide an effective treatment for gastric dysmotility; however, the current commercially available device requires surgical implantation for long-term stimulation and is powered by a nonrechargeable battery. OBJECTIVE To test and describe endoscopic implantation techniques and testing of stimulation of a novel, wireless, batteryless, gastric electrical stimulation (GES) device. DESIGN Endoscopic gastric implantation techniques were implemented, and in vivo gastric signals were recorded and measured in a non-survival swine model (n = 2; 50-kg animals). INTERVENTION Five novel endoscopic gastric implantation techniques and stimulation of a novel, wireless, batteryless, GES device were tested on a non-survival swine model. MAIN OUTCOME MEASUREMENTS Feasibility of 5 new endoscopic gastric implantation techniques of the novel, miniature, batteryless, wireless GES device while recording and measurement of in vivo gastric signals. RESULTS All 5 of the novel endoscopic techniques permitted insertion and securing of the miniaturized gastrostimulator. By the help of these methods and miniaturization of the gastrostimulator, successful GES could be provided without any surgery. The metallic clip attachment was restricted to the mucosal surface, whereas the prototype tacks, prototype spring coils, percutaneous endoscopic gastrostomy wires/T-tag fasteners, and submucosal pocket endoscopic implantation methods attach the stimulator near transmurally or transmurally to the stomach. They allow more secure device attachment with optimal stimulation depth. LIMITATIONS Non-survival pig studies. CONCLUSION These 5 techniques have the potential to augment the utility of GES as a treatment alternative, to provide an important prototype for other dysmotility treatment paradigms, and to yield insights for new technological interfaces between non-invasiveness and surgery.

Investigation of repeatability of sol-gel iridium oxide pH sensor on flexible substrate

In this paper, we presented the fabrication process of miniature pH sensor arrays on flexible polymer substrates. The repeatability of the sensors based on sol-gel fabrication processes was investigated. The sensor repeatability was characterized with linearity, decay time, environmental parameter control and potential stability. Similar linear responses were found in different batches of sensor arrays. Near super- Nernstian responses were measured on each sensor with slope ranges from -71.6 to -110 mV/pH within a pH range between 2 and 12. The response times were compared in different batches. Six to twenty five seconds of average decay time were shown in each sample repeatedly. Three sensors showed the close potential response in different volumes of pH buffer solution. The sensor showed good stability in each step of the titration process between pH values of 1.8 and 11.9. The peak and saturated potential values presented high correlation with pH values with minor noises. The results showed good sensitivity, stability and repeatability using the sol-gel processes for iridium-oxide pH sensors on flexible substrates.

Wireless implants for in vivo diagnosis and closed-loop treatment

In this presentation, we will review and discuss recent advances in the research of wireless telemetry for medical applications in our group at UT-Arlington, particularly those based on a similar platform for in vivo monitoring of physiological parameters. System for recording ECoG signals in brain, recording in vivo gastric myoelectric activities in stomach, sensing in vivo strain variations in bladder, and detecting reflux episodes in esophagus have been demonstrated. These systems consist of passive transducers for physiological signal transduction and an active transceiver for signal relay and recording. The real-time in vivo physiological signal acquisition and related neuro-/gastro-stimulation form a closed loop between the human body and control electronics. Continuous feedback mechanisms that could be implemented in the closed loop provide treatment strategies for optimization to reach a desired comfort level for individual patient. The wireless systems quantitatively document symptoms and associated physiological signals over a long term while allowing the patients to resume regular daily activities. This will enable more precise diagnosis and prognosis of diseases for the caregivers.

A patch antenna-based strain sensor for structural health monitoring

A passive strain sensor was investigated using patch antennas. For early damage detection in structures due to external loads, reliable strain information is necessary. A noninvasive method of measuring strain using a patch antenna was investigated to overcome the limitations of existing strain sensing technologies. The metal patch antenna was made on a thin sheet of low-loss polymer with a ground plane on the opposite side. When fed with RF signals, the patch antenna radiates at its resonant frequency. The resonant frequency of the patch antenna varies with its dimensions. Strain-induced change in the dimensions results in a shift in the resonant frequency. A single-frequency antenna, designed and simulated using the Sonnet simulation tool, has a resonant frequency corresponding to its length, so the antenna is sensitive only to the length-direction strain yet insensitive to the width-direction strain. Effect of strain on frequency shift and its sensitivity to strain were calculated. The antenna was fabricated using conventional micromachining techniques. Effects of strain on resonant frequency were verified experimentally and in good agreement with simulated results.