Passive Wireless Pressure Sensing for Gastric Manometry

Intelligent Ureteral Stent Placeable via Standard Procedure for Kidney Pressure Telemetry: An Ex-Vivo Study

This paper reports the first telemetric ureteral stent compatible with common placement procedure, enabling wireless sensing and detection of ureteral obstruction and resultant kidney swelling known as hydronephrosis at an early stage. This sensor-integrated "intelligent" ureteral stent is prototyped via the design and fabrication approaches that raise the practicality of the device and tested in a harvested swine kidney-ureter model ex vivo. Leveraging a polymeric double-J stent and micro-electro-mechanical systems technology, the intelligent stent is built by embedding micro pressure sensors and a radiofrequency antenna, forming a resonant circuit that enables wireless kidney pressure monitoring in an operating frequency of 40-50 MHz. The stent device is entirely packaged with Parylene-C for both biocompatibility and electrical insulation of the device in order to function in the real environment including urine, an electrically conductive liquid. A comparison between the results measured in in-vitro and ex-vivo settings show a good match in the sensitivity to applied pressure. In particular, the ex-vivo test in the kidney-ureter model pressurized with artificial urine in a cycled manner demonstrates wireless pressure tracking with a response of 1.3 kHz/mmHg, over pressures up to 37 mmHg that well covers a range of pressure increase known for chronic obstruction. This testing is enabled by the prototype placement into the ex-vivo model using the standard stenting technique and tools without noticeable functional degradation or failures, showing potential compatibility of the device with today's clinical need as a ureteral stent.

Smart capsules for sensing and sampling the gut: status, challenges and prospects

Smart capsules are developing at a tremendous pace with a promise to become effective clinical tools for the diagnosis and monitoring of gut health. This field emerged in the early 2000s with a successful translation of an endoscopic capsule from laboratory prototype to a commercially viable clinical device. Recently, this field has accelerated and expanded into various domains beyond imaging, including the measurement of gut physiological parameters such as temperature, pH, pressure and gas sensing, and the development of sampling devices for better insight into gut health. In this review, the status of smart capsules for sensing gut parameters is presented to provide a broad picture of these state-of-the-art devices while focusing on the technical and clinical challenges the devices need to overcome to realise their value in clinical settings. Smart capsules are developed to perform sensing operations throughout the length of the gut to better understand the body's response under various conditions. Furthermore, the prospects of such sensing devices are discussed that might help readers, especially health practitioners, to adapt to this inevitable transformation in healthcare. As a compliment to gut sensing smart capsules, significant amount of effort has been put into the development of robotic capsules to collect tissue biopsy and gut microbiota samples to perform in-depth analysis after capsule retrieval which will be a game changer for gut health diagnosis, and this advancement is also covered in this review. The expansion of smart capsules to robotic capsules for gut microbiota collection has opened new avenues for research with a great promise to revolutionise human health diagnosis, monitoring and intervention.

Electromechanically Functionalized Ureteral Stents for Wireless Obstruction Monitoring

While millions of ureteral stents are placed in patients with urinary tract issues around the world every year, hydronephrosis still poses great danger to these patients as a common complication. In the present work, an intelligent double-J ureteral stent equipped with a micro pressure sensor and antenna circuitry is investigated and prototyped toward enabling continuous wireless monitoring of kidney pressure to detect a ureteral obstruction and the resultant hydronephrosis via the indwelling stent. This electromechanically functionalized "intelligent" ureteral stent acts as a radiofrequency resonator with a pressure-sensitive resonant frequency that can be interrogated using an external antenna to track the local pressure. The prototype passes mechanical bending tests of up to 15 cm radius of curvature and shows wireless sensing with a sensitivity of 3.1 kHz/mmHg in artificial urine, which represents 25× enhancement over the preceding design, using an in vitro model with test tissue layers and a pressure range that functions within the conditions found in hydronephrotic conditions. These promising results are expected to propel intelligent ureteral stent technology into further clinical research.

Biocompatible and Long-Term Monitoring Strategies of Wearable, Ingestible and Implantable Biosensors: Reform the Next Generation Healthcare

Sensors enable the detection of physiological indicators and pathological markers to assist in the diagnosis, treatment, and long-term monitoring of diseases, in addition to playing an essential role in the observation and evaluation of physiological activities. The development of modern medical activities cannot be separated from the precise detection, reliable acquisition, and intelligent analysis of human body information. Therefore, sensors have become the core of new-generation health technologies along with the Internet of Things (IoTs) and artificial intelligence (AI). Previous research on the sensing of human information has conferred many superior properties on sensors, of which biocompatibility is one of the most important. Recently, biocompatible biosensors have developed rapidly to provide the possibility for the long-term and in-situ monitoring of physiological information. In this review, we summarize the ideal features and engineering realization strategies of three different types of biocompatible biosensors, including wearable, ingestible, and implantable sensors from the level of sensor designing and application. Additionally, the detection targets of the biosensors are further divided into vital life parameters (e.g., body temperature, heart rate, blood pressure, and respiratory rate), biochemical indicators, as well as physical and physiological parameters based on the clinical needs. In this review, starting from the emerging concept of next-generation diagnostics and healthcare technologies, we discuss how biocompatible sensors revolutionize the state-of-art healthcare system unprecedentedly, as well as the challenges and opportunities faced in the future development of biocompatible health sensors.

Passive Wireless Pressure Gradient Measurement System for Fluid Flow Analysis

Using distributed MEMS pressure sensors to measure small flow rates in high resistance fluidic channels is fraught with challenges far beyond the performance of the pressure sensing element. In a typical core-flood experiment, which may last several months, flow-induced pressure gradients are generated in porous rock core samples wrapped in a polymer sheath. Measuring these pressure gradients along the flow path requires high resolution pressure measurement while contending with difficult test conditions such as large bias pressures (up to 20 bar) and temperatures (up to 125 °C), as well as the presence of corrosive fluids. This work is directed at a system for using passive wireless inductive-capacitive (LC) pressure sensors that are distributed along the flow path to measure the pressure gradient. The sensors are wirelessly interrogated with readout electronics placed exterior to the polymer sheath for continuous monitoring of experiments. Using microfabricated pressure sensors that are smaller than ø15 × 3.0 mm³, an LC sensor design model for minimizing pressure resolution, accounting for sensor packaging and environmental artifacts is investigated and experimentally validated. A test setup, built to provide fluid-flow pressure differentials to LC sensors with conditions that mimic placement of the sensors within the wall of the sheath, is used to test the system. Experimental results show the microsystem operating over full-scale pressure range of 20,700 mbar and temperatures up to 125 °C, while achieving pressure resolution of <1 mbar, and resolving gradients of 10-30 mL/min, which are typical in core-flood experiments.

Novel Production Methods of Polyhydroxyalkanoates and Their Innovative Uses in Biomedicine and Industry

Polyhydroxyalkanoate (PHA), a biodegradable polymer obtained from microorganisms and plants, have been widely used in biomedical applications and devices, such as sutures, cardiac valves, bone scaffold, and drug delivery of compounds with pharmaceutical interests, as well as in food packaging. This review focuses on the use of polyhydroxyalkanoates beyond the most common uses, aiming to inform about the potential uses of the biopolymer as a biosensor, cosmetics, drug delivery, flame retardancy, and electrospinning, among other interesting uses. The novel applications are based on the production and composition of the polymer, which can be modified by genetic engineering, a semi-synthetic approach, by changing feeding carbon sources and/or supplement addition, among others. The future of PHA is promising, and despite its production costs being higher than petroleum-based plastics, tools given by synthetic biology, bioinformatics, and machine learning, among others, have allowed for great production yields, monomer and polymer functionalization, stability, and versatility, a key feature to increase the uses of this interesting family of polymers.

Rapid Characterization of Solid Tumors Using Resonant Sensors

Cancer continues to be a significant cause of non-traumatic pediatric mortality. Diagnosis of pediatric solid tumors is paramount to prescribing the correct treatment regimen. Recent efforts have focused on non-invasive methods to obtain tumor tissues, but one of the challenges encountered is the ability to obtain an adequate amount of viable tissue. In this study, a wireless, inductor-capacitor (LC) sensor was employed to detect relative permittivity of pediatric tumor tissues. There is a comparison of resonant frequencies of tumor tissues between live versus dead tissues, the primary tumor tissue versus tissue from the organs of origin or metastasis, and treated versus untreated tumors. The results show significant shifts in resonant frequencies between the comparison groups. Dead tissues demonstrated a significant shift in resonant frequencies compared to alive tissues. There were significant differences between the resonant frequencies of normal tissues versus tumor tissues. Resonant frequencies were also significantly different between primary tumors compared to their respective metastases. These data indicate that there are potential clinical applications of LC technology in the detection and diagnosis of pediatric solid tumors.

Cuffless Blood Pressure Monitoring: Academic Insights and Perspectives Analysis

In recent decades, cuffless blood pressure monitoring technology has been a point of research in the field of health monitoring and public media. Based on the web of science database, this paper evaluated the publications in the field from 1990 to 2020 using bibliometric analysis, described the developments in recent years, and presented future research prospects in the field. Through the comparative analysis of keywords, citations, H-index, journals, research institutions, national authors and reviews, this paper identified research hotspots and future research trends in the field of cuffless blood pressure monitoring. From the results of the bibliometric analysis, innovative methods such as machine learning technologies related to pulse transmit time and pulse wave analysis have been widely applied in blood pressure monitoring. The 2091 articles related to cuffless blood pressure monitoring technology were published in 1131 journals. In the future, improving the accuracy of monitoring to meet the international medical blood pressure standards, and achieving portability and miniaturization will remain the development goals of cuffless blood pressure measurement technology. The application of flexible electronics and machine learning strategy in the field will be two major development directions to guide the practical applications of cuffless blood pressure monitoring technology.

A Circularly Polarized Implantable Rectenna for Microwave Wireless Power Transfer

A circularly polarized implantable antenna integrated with a voltage-doubled rectifier (abbr., rectenna) is investigated for microwave wireless power transfer in the industrial, scientific, and medical (ISM) band of 2.4–2.48 GHz. The proposed antenna is miniaturized with the dimensions of 7.5 mm × 7.5 mm × 1.27 mm by etching four C-shaped open slots on the patch. A rectangular slot truncated diagonally is cut to improve the circular polarization performance of the antenna. The simulated impedance bandwidth in a three-layer phantom is 30.4% (1.9–2.58 GHz) with |S11| below −10 dB, and the 3-dB axial-ratio bandwidth is 16.9% (2.17–2.57 GHz). Furthermore, a voltage-doubled rectifier circuit that converts RF power to DC power is designed on the back of the antenna. The simulated RF-to-DC conversion efficiency can be up to 45% at the input power of 0 dBm. The proposed rectenna was fabricated and measured in fresh pork to verify the simulated results and evaluate the performance of wireless power transfer.

Fabrication of Suspended PMMA-Graphene Membrane for High Sensitivity LC-MEMS Pressure Sensor

The LC-MEMS pressure sensor is an attractive option for an implantable sensor. It senses pressure wirelessly through an LC resonator, eliminating the requirement for electrical wiring or a battery system. However, the sensitivity of LC-MEMS pressure sensors is still comparatively low, especially in biomedical applications, which require a highly-sensitive sensor to measure low-pressure variations. This study presents the microfabrication of an LC wireless MEMS pressure sensor that utilizes a PMMA-Graphene (PMMA/Gr) membrane supported on a silicon trench as the deformable structure. The (PMMA/Gr) membrane was employed to increase the sensor's sensitivity due to its very low elastic modulus making it easy to deform under extremely low pressure. The overall size of the fabricated sensor was limited to 8 mm × 8 mm. The experimental results showed that the capacitance value changed from 1.64 pF to 12.32 pF when the applied pressure varied from 0 to 5 psi. This capacitance variation caused the frequency response to change from 28.74 MHz to 78.76 MHz. The sensor sensitivity was recorded with a value of 193.45 kHz/mmHg and a quality factor of 21. This study concludes that the (PMMA/Gr) membrane-based LC-MEMS pressure sensor has been successfully designed and fabricated and shows good potential in biomedical sensor applications.

In vitro models to evaluate ingestible devices: Present status and current trends

Orally ingestible medical devices offer significant opportunity in the diagnosis and treatment of gastrointestinal conditions. Their development necessitates the use of models that simulate the gastrointestinal environment on both a macro and micro scale. An evolution in scientific technology has enabled a wide range of in vitro, ex vivo and in vivo models to be developed that replicate the gastrointestinal tract. This review describes the landscape of the existing range of in vitro tools that are available to characterize ingestible devices. Models are presented with details on their benefits and limitations with regards to the evaluation of ingestible devices and examples of their use in the evaluation of such devices is presented where available. The multitude of models available provides a suite of tools that can be used in the evaluation of ingestible devices that should be selected on the functionality of the device and the mechanism of its function.

Smart pills for gastrointestinal diagnostics and therapy

Ingestible smart pills have the potential to be a powerful clinical tool in the diagnosis and treatment of gastrointestinal disease. Though examples of this technology, such as capsule endoscopy, have been successfully translated from the lab into clinically used products, there are still numerous challenges that need to be overcome. This review gives an overview of the research being done in the area of ingestible smart pills and reports on the technical challenges in this field.

Systematic Review of Diagnostic Sensors for Intra-Abdominal Pressure Monitoring

Intra-abdominal pressure (IAP) is defined as the steady-state pressure within the abdominal cavity. Elevated IAP has been implicated in many medical complications. This article reviews the current state-of-the-art in innovative sensors for the measurement of IAP. A systematic review was conducted on studies on the development and application of IAP sensors. Publications from 2010 to 2021 were identified by performing structured searches in databases, review articles, and major textbooks. Sixteen studies were eligible for the final systematic review. Of the 16 articles that describe the measurement of IAP, there were 5 in vitro studies (31.3%), 7 in vivo studies (43.7%), and 4 human trials (25.0%). In addition, with the advancement of wireless communication technology, an increasing number of wireless sensing systems have been developed. Among the studies in this review, five presented wireless sensing systems (31.3%) to monitor IAP. In this systematic review, we present recent developments in different types of intra-abdominal pressure sensors and discuss their inherent advantages due to their small size, remote monitoring, and multiplexing.

Next-generation ingestible devices: sensing, locomotion and navigation

There is significant interest in exploring the human body's internal activities and measuring important parameters to understand, treat and diagnose the digestive system environment and related diseases. Wireless capsule endoscopy (WCE) is widely used for gastrointestinal (GI) tract exploration due to its effectiveness as it provides no pain and is totally tolerated by the patient. Current ingestible sensing technology provides a valuable diagnostic tool to establish a platform for monitoring the physiological and biological activities inside the human body. It is also used for visualizing the GI tract to observe abnormalities by recording the internal cavity while moving. However, the capsule endoscopy is still passive, and there is no successful locomotion method to control its mobility through the whole GI tract. Drug delivery, localization of abnormalities, cost reduction and time consumption are improvements that can be gained from having active ingestible WCEs. In this article, the current technological developments of ingestible devices including sensing, locomotion and navigation are discussed and compared. The main features required to implement next-generation active WCEs are explored. The methods are evaluated in terms of the most important features such as safety, velocity, complexity of design, control, and power consumption.

16.8 nW Ultra-Low-Power Energy Harvester IC for Tiny Ingestible Sensors Sustained by Bio-Galvanic Energy Source

Herein, we present a 16.8 nW ultra-low-power (ULP) energy harvester integrated circuit (IC) for ingestible biomedical sensors. The energy harvester can be powered from the electro-galvanic operation inside a human body, which provides a sustainable and long-term energy source. The challenge of dealing with relatively high input impedance (∼kΩ) of the bio-galvanic energy source is addressed by introducing two design techniques. The first technique is an adaptive V_MPP-controlled algorithm (AVCA) for a maximum power point tracking (MPPT) controller, and the second technique is a ULP delay-line-based zero current switching (ZCS) controller. Different from the conventional fractional open-circuit voltage (FOCV) method for MPPT, the proposed AVCA allows continuous source tracking without detachment of the harvester from the source. The ZCS operation is achieved using a delay-line controller without using either a comparator or an opamp. The proposed AVCA is realized using a 12.1 nW MPPT controller. Successful ZCS operation is achieved using a 2.1 nW delay controller. Overall power consumption of the IC is 16.8 nW. The converter has been fabricated in a 0.18 μm CMOS process with 2 μm thick top-metal option. The measured result shows that the converter achieves a peak efficiency of 72.1% to generate 507 nW output power. The ULP operation allows a significant reduction in electrode size down to the submillimeter scale (∼0.4 mm²), demonstrating the good potential of the proposed energy harvester IC.

An Ingestible Electronics for Continuous and Real-Time Intraabdominal Pressure Monitoring

Abdominal compartment syndrome can be treated through decompressive surgery if intraabdominal hypertension (IAH) can be detected in time. Treatment delays due to manual, conventional intravesical pressure (IVP) monitoring using a Foley catheter have been reported. In this work, we present an innovative gastrointestinal intraluminal pressure (GIP) measurement-based method to monitor and improve pressure-guided relief of intraabdominal pressure (IAP). A novel algorithm for detecting IAH in the gastrointestinal tract of a live porcine model is reported. A wireless pressure-sensing capsule (10 × 13 mm) was developed for absolute measurement. The IAP was estimated during artificial pneumoperitoneum. The pressure waveform-based measurements indicated that the wireless pressure sensor could be used to predict IAP. To enhance GIP monitoring for predicting IAH, the proposed continuous ingestible wireless electronics-based pressure waveform measurement device can be used as a complement to existing modalities. The use of the proposed pressure measurement and communication technology can help provide valuable data for digital health platforms.