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Urinary bladder volume monitoring can benefit from contactless measurements, as alternative to the traditional medical methods of transurethral catheterization or ultrasound examination. The emerging modality of Magnetic Induction Tomography (MIT) offers the possibility for estimation of the intravesical volume in the physiological and pathological states using conductivity map reconstructions of the tissues present in the pelvic region. Within MIT, eddy currents originating from the conductive urine can produce their own magnetic field in response to an external magnetic source that is susceptible of being detected outside the body by means of a static ring of sensing coils. However, the ill-conditioned and ill-posed nature of the MIT Inverse Problem make the numerical implementation and conductivity estimation highly laborious. In this paper, we present a rotational frame model based on the MIT principles with application in urodynamic studies, which allows to extend the number of contactless measurements without increasing the overall dimension of the simulation domain, at the expense of solving multiple MIT Forward Problems. On the inversion process, the single-step Gauss-Newton method with Laplacian regularizer is recruited to estimate the bladder volume non-invasively and remotely (estimation error of 19%) using a simplified (quasi 2D) approximation to the distribution of eddy currents in the examined region, therefore paving the way for this technique to surpass the current limitations found in intravesical volume monitoring.

Ultrasounds (US) are one of the most used imaging and sensing modalities in the medical field. Apart from therapeutic applications, most interactions between the acoustic waves and tissue occur passively without any substantial modification to the physiology of the later. However, US can also be used to power actively implanted devices with the same energy-carrying waves. In this article, we propose small-form implantable devices for monitoring of physiological parameters in soft tissue (bio-potential and temperature), together with electric stimulation using a specially designed handheld scanning probe. The ultra-low power consumption of the devices ( $110~\mu \text{W}$ in average) and operation with harvested voltage levels as low as 0.5 V, allows deployment up to 25 mm from the probe. Sensing data is then transmitted by an ON-OFF Keying modulation scheme (OOK) and detected by an overly sensitive demodulator with carrier-to-noise ratio of– 57 dB. We went further to incorporate electronic modules for tissue impedance imaging in situ for detection of impairment to the normal conductivity of tissues caused by inflammation, bacterial infection or cancer. Potential applications of this technology include the detection of endogenous and exogenous sources of electric potential, useful in the evaluation of soft tissue healing and recovery after surgery, as a diagnostic complement to the more traditional methods of US imaging or alternative to other implantable devices, which are limited by inductive and radiofrequency powering links.

Excessive stress is one of the main causes of mental illness. Long-term exposure of stress could affect one's physiological wellbeing (such as hypertension) and psychological condition (such as depression). Multisensory information such as heart rate variability (HRV) and pH can provide suitable information about mental and physical stress. This paper proposes a novel approach for stress condition monitoring using disposable flexible sensors. By integrating flexible amplifiers with a commercially available flexible polyvinylidene difluoride (PVDF) mechanical deformation sensor and a pH-type chemical sensor, the proposed system can detect arterial pulses from the neck and pH levels from sweat located in the back of the body. The system uses organic thin film transistor (OTFT)-based signal amplification front-end circuits with modifications to accommodate the dynamic signal ranges obtained from the sensors. The OTFTs were manufactured on a low-cost flexible polyethylene naphthalate (PEN) substrate using a coater capable of Roll-to-Roll (R2R) deposition. The proposed system can capture physiological indicators with data interrogated by Near Field Communication (NFC). The device has been successfully tested with healthy subjects, demonstrating its feasibility for real-time stress monitoring.

In this article, a novel method for measuring the volume of the urinary bladder non-invasively is presented that relies on the principles dictated by Electrical Impedance Tomography (EIT). The electronic prototype responsible for injecting innocuous electrical currents to the lower abdominal region and measuring the developed voltage levels is fully described, as well as the computational models for resolution of the so-called Forward and Inverse Problems in Imaging. The simultaneous multi-tone injection of current provided by a high performance Field Programmable Gate Array (FPGA), combined with impedance estimation by the Discrete Fourier Transform (DFT) constitutes a novelty in Urodynamics with potential to monitor continuously the intravesical volume of patients in a much faster and comfortable way than traditional transurethral catheterization methods. The resolution of the Inverse Problem is performed by the Gauss-Newton method with Laplacian regularization, allowing to obtain a sectional representation of the volume of urine encompassed by the bladder and surrounding body tissues. Experimentation has been carried out with synthetic phantoms and human subjects with results showing a good correlation between the levels of abdominal admittivity acquired by the EIT system and the volume of ingested water.

Cardiac-related diseases are still the number one cause of death worldwide. Methods and technologies to suppress this problem are currently being investigated by integrating electrocardiographic (ECG) monitoring with other sensing modalities in order to detect these diseases more accurately and in due course of time. In this paper, we propose a battery-less and flexible device to be worn as a chest patch for monitoring cardiac and hemodynamic parameters through electrical and acoustic measurements, combined with sweat pH level estimation and skin temperature, by swiping a smartphone over the patch area for enough time (≃5 seconds) to allow adequate acquisition and estimation of the aforementioned parameters. Fast screening of vital signals from patients in ambulatory or emergency scenarios can thus be achieved by this Near Field Communication (NFC) powered device, as well as home or office monitoring for those individuals suffering from diseases affecting the hemodynamic, cardiac and endocrine parameters detected by the proposed technology. Current consumption of the device is 1 mA for harvested levels of 1.8 V, yielding a power requirement of 1.8 mW. Within these conditions, the sensitivities achieved by each sensing modality are 42 mV/unit for pH, 0.12 °C for temperature, 48 dB SNR for ECG and -56 dBA for acoustic measurements.

Sound monitoring from sources inside the human body can have important diagnostic relevance in medicine. Cardiac sounds originated from the pumping activity of the heart structure is such an example, with valuable cardiovascular parameters being extracted from the signal, including heart rate (HR) and the systolic intervals. Novel non-invasive methods for early detection of potential life-threatening risks convoyed by unbalanced cardiovascular parameters are essential to reduce the mortality rates associated with cardiac diseases nowadays. In this paper, we propose a small-form wearable device for longterm monitoring of the cardiac sounds through a miniaturized microphone in contact with the body surface at specific locations, which extend from the chest region to the upper and lower body parts. Powered by battery, the device can measure signals for a consecutive period of 28 h in continuous recording mode that is extensive up to 7 days in discontinuous mode, achieving signal amplitude resolution of 0.81 μV and optimal bandwidth between 5 to 20 Hz (infrasound range). The proposed device was able to detect cardiac sound patterns in locations as distant as the forehead, wrist, or ankle, thus paving the way to the use of acoustic signals for wearable heartbeat estimators still relying on optical or bio-potential methods, while replacing the obtrusive and expensive cardiography equipment dedicated to the estimation of the systolic intervals directly from the chest.

Implantable devices represent the future of remote medical monitoring and administration of both chemical and physical therapies to the patients. Although some of these devices are already in the market, the security mechanisms deployed inside them to withstand deliberate external influence are still decades away from the robust digital data security schemes employed in modern distributed networks these days. Medical data theft, spoofing, and disclosure pose serious threats that can ultimately lead to individual and social stigmas or even death. In this article, we present a small-form and batteryless implantable device with acquisition channels for biopotential (30-dB gain and 16-Hz bandwidth), arterial pulse oximetry, and temperature (0.12°C accuracy) recordings, suitable for cardiovascular, neuronal, and endocrine parameters assessment. The proposed device is powered by the near-field communication (NFC) interface with an external mobile phone, with a power consumption of 0.9 mW and achieving the full operation for distances close to 1 cm under the skin. In situ encryption of the acquired physiological signals is performed by a lightweight and short-term symmetric-key distribution scheme with data stream hopping, in order to ensure secure data transference over the air between the patient and trusted entities only, complemented by data storage, processing, and recovery through a medical blockchain type of network that involves the main stakeholders inside a medical community.

With an increasingly aging population and a need for decentralization of health care and remote, at-home, and bedside monitoring, there is a growing necessity for wearables and implantables with advanced capabilities that provide data suitable for clinical diagnostics. In this chapter, musculoskeletal applications serve as the exemplar for these technologies. The clinical drives for sensing and augmented therapy are highlighted for conditions including bone fractures, nonunions, ligament tears, stroke, and arthritis. Piezoresistive strain sensors based on elastomeric composites, hydrogels, liquid-metals, and magnetoelastic sensors are discussed, together with electrophysiological recordings to monitor mechanical loading and muscle activity coupled with discussions on bioimpedance, motion sensors, hydrogels, regenerative methods, and electrical stimulation. Passive approaches based on resonant systems with sensing capabilities are highlighted as an approach for implantables. The necessity for biocompatibility and appropriate packaging, as well as the potential for biodegradability, are also emphasized.

Aims Recently, the cardiovascular outcomes for people using anticoagulation strategies (COMPASS) trial demonstrated that dual therapy reduced cardiovascular outcomes compared with aspirin alone in patients with stable atherosclerotic disease. Methods and results We sought to assess the proportion of patients eligible for the COMPASS trial and to compare the epidemiology and outcome of these patients with those without COMPASS inclusion or with any exclusion criteria in a contemporary, nationwide cohort of patients with stable coronary artery disease. Among the 4068 patients with detailed information allowing evaluation of eligibility, 1416 (34.8%) did not fulfil the inclusion criteria (COMPASS-Not-Included), 841 (20.7%) had exclusion criteria (COMPASS-Excluded), and the remaining 1811 (44.5%) were classified as COMPASS-Like. At 1 year, the incidence of major adverse cardiovascular event (MACE), a composite of cardiovascular death, myocardial infarction, and stroke, was 0.9% in the COMPASS-Not-Included and 2.0% in the COMPASS-Like (P = 0.01), and 5.0% in the COMPASS-Excluded group (P Conclusion In a contemporary real-world cohort registry of stable coronary artery disease, most patients resulted as eligible for the COMPASS. These patients presented a considerable annual risk of MACE that consistently increases in the presence of multiple risk factors.

All wearable and implantable devices require power to operate, while they also need to have communication capabilities to transmit sensory data to secondary devices to aid clinical decision making, while often bidirectional communication is required for the proper control of the wearable or implantable device. Traditionally batteries are used for power. Batteries and supercapacitors are thus initially discussed, with a focus on flexible and stretchable implementations. Battery-powered systems face the issue that their power will eventually be depleted. Biofuel cells are a form of energy harvesting that has significantly advanced over the last few years, with interests particularly focused around energy generation via enzymatic fuel cells exploiting metabolites, such as glucose and lactate that can be found in abundance in biofluids, such as sweat and blood. Recent advances as well as the fundamental architectures, materials, enzymes, and operational principles are elucidated in detail. Alternative energy harvesting approaches, such as piezoelectricity are also briefly discussed. These are followed by an overview of wireless powering and communication methods, which includes inductive, capacitive, electromagnetic, and galvanic couplings, as well as modulation methods. The communication channel needs to be secure, since personal and sensitive information are transmitted, while when bidirectional communication takes place, involving the transmission of data for the control of the wearable or implantable device, safety becomes also an issue.

Accurate detection of blood biomarkers related to neurodegenerative diseases could provide a shortcut to identifying early stage patients before the onset of symptoms. The specificity, selectivity and operational requirements of the current technologies, however, preclude their use in the primary clinical setting for early detection. Graphene, an emerging 2D nanomaterial, is a promising candidate for biosensing which has the potential to meet the performance requirements and enable cost-effective, portable and rapid diagnosis. In this review, we compare graphene-based immunosensing technologies with conventional enzyme-linked immunosorbent assays and cutting-edge single molecule array techniques for the detection of blood-based neurodegenerative biomarkers. We cover the progress in electrical, electrochemical and optical graphene-based immunosensors and outline the barriers that slow or prevent the adoption of this emerging technology in primary clinical settings. We also highlight the possible solutions to overcome these barriers with an outlook on the future of the promising, graphene immunosensor technology.

Infection by the parasite of malaria is a serious healthcare problem for populations residing primarily in tropical and subtropical countries. Early detection of the disease is essential to reduce both the mortality rate and spreading of the disease in the infected areas. Current methods for malaria diagnosis still rely on microscopic analysis of blood smears, which is a time-consuming and expensive process, in addition of requiring trained examiners to perform the analysis. In this paper, we introduce a novel fast screening tool for malaria based on a portable blood impedance analyzer. The simultaneous multi-tone injection of current and voltage detection of the device allow reducing the screening time (order of seconds) while enhancing the differences in impedance signal registered among frequencies to increase parasitemia level discrimination. We went further to demonstrate the possibility of directly applying the device on blood samples collected from volunteers to distinguish between infected and non-infected samples. Minimum parasitemia level discriminated was 0.0078% (or, equivalently 390 parasites/μl), which closely approaches the international standard set to 200 parasites/μl. Finally, we also show the frequency dependency of ring-synchronized and unsynchronized blood samples, which can constitute the basis for development of a point-of-care and laboratory-free method to distinguish different stages of malaria infection in economic stagnated communities.

Aims We evaluated the 1-year clinical events, pharmacological management, and quality of life in a contemporary cohort of stable coronary artery disease (CAD) patients managed by cardiologists. Methods and results START (STable Coronary Artery Diseases RegisTry) was a prospective, observational, nationwide study that enrolled 5070 stable CAD patients over 3 months in 183 cardiology centres in Italy. At 1 year, 4790 (94.5%) patients had data on vital status. Death occurred in 107 (2.2%) patients and the cause of death was cardiovascular in 41 (38.3%) of cases. Among the 4775 patients with follow-up data on clinical events available, a hospitalization due to cardiovascular and non-cardiovascular causes occurred in 523 (11.0%) and in 231 (4.8%) of cases, respectively. Over 60% of patients reported as ‘no problems’ in all domains (61.4–84.5%) of the EuroQoL quality of life 5D-5L questionnaire. Among the 3239 patients with clinical visit/telephone interview at follow-up, in whom optimal medical therapy (OMT; aspirin or thienopyridine, β-blocker, and statin) was prescribed at enrolment, 2971 (91.7%) were still receiving OMT at follow-up. At multivariable analysis, only increasing age (odds ratio 0.98; 95% confidence interval 0.97–0.99; P = 0.04) resulted as independent negative predictor of OMT persistence at 1 year from enrolment. Conclusion In this large, contemporary registry, stable CAD patients managed by cardiologists presented a high rate of clinical events at 1 year. Nevertheless, the persistence to OMT and quality of life appeared reasonable.

Recent developments in wearable electronics have fueled research into new materials, sensors, and microelectronic technologies for the realization of devices that have increased functionality and performance. This is further enhanced by advances in fabr ication methods and printing techniques, stimulating research on implantables and the advancement of existing medical devices. This article provides an overview of new designs, embodiments, fabrication methods, instrumentation, and informatics as well as the challenges in developing and deploying such devices and clinical applications that can benefit from them. The need for and use of these technologies across the perioperative surgical-care pathway are highlighted, along with a vision for the future and how these tools can be adopted by potential end users and health-care systems.

Sleep perturbations are well-know causes of general uneasiness for many individuals during the daily course of life. Environmental and social stressors derived from the modern lifestyle can affect the quality of sleep, dis-regulating some of the physiological processes taking place during this body and mind resting period. In this paper, we propose a small-form and wearable device for electroencephalography (EEG) monitoring, combined with head motion detection (acceleration) and chemical information collected from off-body sensors targeting sweat pH and cortisol measurements. The incorporated EEG channel has been designed with a cascaded amplification gain of 80 dB, whereas the sensitivity achieved for the developed pH sensor is 48 mV/unit and, for cortisol, a 7 µA current decay is obtained per decade of concentration, within the range from 1 µM to 1 fM. Potential applications of the device include the tracking of the aforementioned chemical analytes during a circadian cycle, which mediate vital brain functions such as neuronal plasticity, maturation, memory formation and cognition, with repercussions in the EEG patterns detected externally. Future incorporation into an eye-shade (EEG and acceleration) and earplug (chemical sensors) will help monitoring the sleep process more easily and accurately, without causing discomfort or pain for patients suffering from sleep-related diseases or other brain conditions.

Contact-based skin measurements represent the standard setup for biopotential acquisition in clinical practice. The techniques for ECG, EMG, EOG or EEG recordings have remained largely unchanged for the past decades, apart from electronic circuit miniaturization and ease of connectivity to the Internet of Things. Electrode placement over the skin needs to consider the endogenous currents generated by the body flowing into the terminal inputs of an external amplifier. Although much effort has been devoted lately to the design of electrodes with better conductivity and signal-to-noise ratios, a physical connection between the skin and electronics is still necessary to accommodate the circulation of these currents. In this paper, we present a capacitive sensor for distant ECG acquisition without physical contact with the skin, combining the non-invasiveness nature of the method with contact-less measurements. A high impedance front-end amplifier assures a deviation of the corner frequency to the mHz range for the high-pass filter generated between body surface and amplifier, thus allowing the detection of cardiac events produced by slowly moving AC currents.

Ultrasounds (US) has been used in the past decades as a non-invasive imaging modality. Although employed extensively in clinical applications for soft tissue imaging, the acoustic beams can also be used for sensing and actuation for biological implants. In this paper we present a unified three dimensional (3D) computational framework to simulate the performance and response of deeply implanted devices to US stimulation and composed by a double piezoelectric layer with different material composition and configurations. The model combines the temporally-invariant distribution of the scattered pressure field arising from the presence of scatterers and attenuators in the domain of simulation, with the time-delay propagation of waves caused by refraction, to solve the Forward Problem in US within the breast and lower abdominal regions. It was found that a lens-shaped implant produces higher peak echoes in the breast for frequencies ≤ 6 MHz whereas, in the liver, similar strengths are obtained for the lens and disk-shaped implants in the higher spectrum. Regarding material composition, a combination of LiNbO3 with PZT-5A yielded higher amplitude signals, when the double layer thickness is comparable to the wavelength of excitation. Experimental validation of the proposed model was carried out in the presence of a synthetic anatomical phantom of the breast and water tank to investigate the acoustic signals generated by disk-shaped implants when stimulated by external US sources in the harmonic and impulsive regimes of wave propagation. The implantation of a double piezoelectric layer inside the human body can, in the future, provide a high resolution system for the detection of surgical site infection as well as tumour growth and other systemic inflammatory responses originating deeply in soft tissues.

Food intake is a major healthcare issue in developed countries that has become an economic and social burden across all sectors of society. Bad food intake habits lead to increased risk for development of obesity in children, young people and adults, with the latter more prone to suffer from health diseases such as diabetes, shortening the life expectancy. Environmental, cultural and behavioural factors have been appointed to be responsible for altering the balance between energy intake and expenditure, resulting in excess body weight. Methods to counteract the food intake problem are vast and include self-reported food questionnaires, body-worn sensors that record the sound, pressure or movements in the mouth and GI tract or image-based approaches that recognize the different types of food being ingested. In this paper we present an ear-worn device to track food intake habits by recording the acoustic signal produced by the chewing movements as well as the glucose level amperiometrically. Combined with a small camera on a future version of the device, we hope to deliver a complete system to control dietary habits with caloric intake estimation during satiation and deficit during satiety periods, which can be adapted to the physiology of each user.

Monitoring of intrabody cardiovascular parameters can benefit from implantation of miniature devices close to anatomical targets, thereby surpassing signal attenuation problems related to the propagation toward body surface while allowing localized sensing at the target site with higher precision. With proper electronic miniaturization, packaging, robustness, and power consumption reduction, such devices can harvest enough energy from the surrounding environment for proper operation. Herein, a near-field communication (NFC)-powered implantable device with acquisition channels for electrocardiogram, arterial pulse, and temperature measurements is introduced. It has been successfully deployed inside rodents for a 72-h trial period to assess external powering and data communication in living animals. Experimental results obtained by this device demonstrate the potential for providing more reliable diagnostic information than that of external wearable devices.

Skin cancer is a medical condition that is becoming more common in many countries as a result of excessive exposure of individuals to sunlight. The ultraviolet range of the electromagnetic radiation is responsible for 90% of the cases involving the development of melanomas. Additional factors like the skin tone and texture can increase the risk of radiation exposure when the water content retained by the skin starts to drop dramatically. In this paper we present a small, batteryless wearable device that combines the computation of sunlight exposure with the measurement of the impedance of the skin and temperature, at any time of the day and independently of the location of the person wearing the sensor. Results have shown a good performance in tracking the ultraviolet index and the variation of impedance for different levels of skin hydration.

Ultrasounds are a proven medical tool to assess some biological processes, including breast cancer screening, fetal development and blood perfusion. However, ultrasounds also have the potential to deliver power and telemetry capabilities to deeply implant devices, surpassing some of the challenges faced by coils or antennas operating inside the human body. In this paper, we present a small-form implantable device activated by ultrasounds that can perform in situ tissue impedance imaging. The goal is to provide a diagnosis tool to evaluate soft tissue healing after surgery, by searching for areas of bacterial infection as the normal conductivity of tissue will be impaired, a phenomena undetected by standard imaging methods. The benefits that can come from this technology are the reduction of the morbidity rate associated with wound infections and recovery time for patients in hospital. The results obtained by the device have already shown a good performance in tracking conductivity perturbations in two-dimensional domains as part of the experimental setup devised for impedance measurements.

Wearable technology has become ubiquitous in recent years due to the miniaturization of circuit electronics and advances in smart materials that can conform to the requirements posed by the human body, behaviour and experience. Sensors of this type are found attached almost to every body segment, capable of delivering signals even in harsh activity scenarios. The reliability and relevance of the physiological data retrieved by wearables have yet to surpass the conventional technologies in the healthcare system today. In this paper we present a small device incorporated inside an headphone set that continuously monitors the ECG, impedance and acceleration of the head. As opposed to most biometric sensors, ECG measurement relies on non-optical methods by capturing the electrical potential around the ear in both sides of the head, whereas impedance monitoring involves AC stimulation instead of DC, the latter commonly involved in skin galvanic response estimation. Signal processing of impedance parameters is performed in situ using a fast variant of the Discrete Fourier Transform in order to save computational resources and power expenditure from a microcontroller equipped with Bluetooth Low Energy. Applications that can benefit from this device include cardiovascular and stress level assessment of individuals for whom an hearable is a requirement for work or leisure.

Ultrasound imaging is a proven diagnostic tool to assess a myriad of physiological and pathological conditions in patients. Throughout the years, ultrasounds have been used as a passive recording modality where the backscattered echo arising from the interaction of the sound waves with the acoustic properties of the biological tissues helps to identify them. Apart from a wide range of therapeutic applications, the acoustic beam has not yet been explored to actuate within the biological environment in an active way. In this paper we present an implantable electronic device to be actuated remotely by ultrasounds with capabilities for measuring several physiological parameters of tissues: pH, temperature, electrolyte concentration and biopotentials. The small factory form device (with no attached batteries) harvests energy from the incoming ultrasound waves and uses it to power the embedded electronics. It operates from voltage levels as low as 0.8 V and consuming a total current of 60 μA (or an average power consumption of 84 μW) in the active mode when deployed at a distance of 3 cm from the active source of ultrasounds in vitro, excited by a sinusoid at 400 kHz with power density of 20 mWcm-2. The sensor can be actuated by a specifically-designed readout device (as detailed in this paper) or using the traditional medical probes for ultrasound imaging. The actual device can present an alternative to surpass the limitations of inductive and RF-powered sensors implanted in soft tissues.

This paper presents a distributed online method for joint state and parameter estimation in a Jump Markov NonLinear System based on a distributed recursive Expectation Maximization algorithm. State inference is enabled via the use of Rao-Blackwellized Particle Filter and, for the parameter estimation, the E-step is performed independently at each sensor with the calculation of local sufficient statistics. An average consensus algorithm is used to diffuse local sufficient statistics to neighbors and approximate the global sufficient statistics throughout the network. The evaluation of the proposed algorithm is carried out on a Terrain Based Navigation problem where the unknown parameters of the observation noise model contain relevant information about the terrain properties.