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.

This paper presents design and optimization methods for spiral coils utilized for wireless power transfer in wireless medical implant applications. A theoretical model was examined for near-field distributions of spiral-type transmitter antennas in both orthogonal components. Finite-element simulations were performed to verify the theoretical radiation patterns. Receiver antenna voltages were measured at planes of interest as a means to map field distributions. Theoretical, simulation, and experimental results were conducted in free space and they agreed well. Understanding the orthogonal field components and their distributions in various distances between the worn transmitter coil outside the body and the receiver coil of implant that has a much smaller size provides a means to find the optimal location and angle to harvest maximum energy. The analysis method for near-field wireless power transmission can be utilized to determine design strategies of the transmitter spiral coil with considerations also in the amplifier circuit and physical constraints in practical scenarios to obtain maximum power and link efficiency for the implant devices. The method can be extended to investigate field distributions affected by human tissues, which construct a much more complex environment, and will be conducted in future works.

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 (IrO_x) 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 IrO_x 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 IrO_x/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.

Electrospinning and polymer blending have been the focus of research and the industry for their versatility, scalability, and potential applications across many different fields. In tissue engineering, nanofiber scaffolds composed of natural fibers, synthetic fibers, or a mixture of both have been reported. This review reports recent advances in polymer blended scaffolds for tissue engineering and the fabrication of functional scaffolds by electrospinning. A brief theory of electrospinning and the general setup as well as modifications used are presented. Polymer blends, including blends with natural polymers, synthetic polymers, mixture of natural and synthetic polymers, and nanofiller systems, are discussed in detail and reviewed.

In this paper, we investigated the effect of power combining and delivering in multiinput and multioutput wireless energy transmission systems, which consist of more than one transmitter antennas as sources and more than one receiver antennas as loads and repeaters. Theoretical expressions were developed to model the system operation that can be in a large-scale wireless energy network architecture. System characteristics, such as power transfer between antennas, power losses induced in each antenna, wireless efficiency, coil misalignment, and power fluctuation due to the loss of frequency synchronization were examined by theory and verified with experiments. Measurement results matched well with the theory demonstrating the feasibility of combining and delivering power with high efficiencies in large-scale wireless energy transmission systems.

This review provides a comprehensive understanding about how different classes of biomaterials, starting from macroscale to nanoscale, interact with bacteria and viruses to exert their antimicrobial properties through diverse mechanisms of action.