Trick or Heat? Manipulating Critical Temperature-Based Control Systems Using Rectification Attacks

Temperature sensing and control systems are widely used in the closed-loop control of critical processes such as maintaining the thermal stability of patients, or in alarm systems for detecting temperature-related hazards. However, the security of these systems has yet to be completely explored, leaving potential attack surfaces that can be exploited to take control over critical systems. In this paper we investigate the reliability of temperature-based control systems from a security and safety perspective. We show how unexpected consequences and safety risks can be induced by physical-level attacks on analog temperature sensing components. For instance, we demonstrate that an adversary could remotely manipulate the temperature sensor measurements of an infant incubator to cause potential safety issues, without tampering with the victim system or triggering automatic temperature alarms. This attack exploits the unintended rectification effect that can be induced in operational and instrumentation amplifiers to control the sensor output, tricking the internal control loop of the victim system to heat up or cool down. Furthermore, we show how the exploit of this hardware-level vulnerability could affect different classes of analog sensors that share similar signal conditioning processes. Our experimental results indicate that conventional defenses commonly deployed in these systems are not sufficient to mitigate the threat, so we propose a prototype design of a low-cost anomaly detector for critical applications to ensure the integrity of temperature sensor signals.Comment: Accepted at the ACM Conference on Computer and Communications Security (CCS), 201

An Implantable Low Pressure Biosensor Transponder

The human body’s intracranial pressure (ICP) is a critical element in sustaining healthy blood flow to the brain while allowing adequate volume for brain tissue within the relatively rigid structure of the cranium. Disruptions in the body’s maintenance of intracranial pressure are often caused by hemorrhage, tumors, edema, or excess cerebral spinal fluid resulting in treatments that are estimated to globally cost up to approximately five billion dollars annually. A critical element in the contemporary management of acute head injury, intracranial hemorrhage, stroke, or other conditions resulting in intracranial hypertension, is the real-time monitoring of ICP. Currently such monitoring can only take place short-term within an acute care hospital, is prone to measurement drift, and is comprised of externally tethered pressure sensors that are temporarily implanted into the brain, thus carrying a significant risk of infection. To date, reliable, low drift, completely internalized, long-term ICP monitoring devices remain elusive. In addition to being safer and more reliable in the short-term, such a device would expand the use of ICP monitoring for the management of chronic diseases involving ICP hypertension and further expand research into these disorders. This research studies the current challenges of existing ICP monitoring systems and investigates opportunities for potentially allowing long-term implantable bio-pressure sensing, facilitating possible improvements in treatment strategies. Based upon the research, this thesis evaluates piezo-resistive strain sensing for low power, sub-millimeter of mercury resolution, in application to implantable intracranial pressure sensing

A Power-Efficient Bio-Potential Acquisition Device with DS-MDE Sensors for Long-Term Healthcare Monitoring Applications

This work describes a power-efficient bio-potential acquisition device for long-term healthcare applications that is implemented using novel microelectromechanical dry electrodes (MDE) and a low power bio-potential processing chip. Using micromachining technology, an attempt is also made to enhance the sensing reliability and stability by fabricating a diamond-shaped MDE (DS-MDE) that has a satisfactory self-stability capability and superior electric conductivity when attached onto skin without any extra skin tissue injury technology. To acquire differential bio-potentials such as ECG signals, the proposed processing chip fabricated in a standard CMOS process has a high common mode rejection ratio (C.M.R.R.) differential amplifier and a 12-bit analog-to-digital converter (ADC). Use of the proposed system and integrate simple peripheral commercial devices can obtain the ECG signal efficiently without additional skin tissue injury and ensure continuous monitoring more than 70 hours with a 400 mAh battery

Low-Power Instrumentation Amplifier IC Design for ECG System Applications

AbstractThis paper describes the development of a low-power instrumentation amplifier (IA) intended for use in recording of the human electrocardiogram (ECG). With the wide-swing cascade bias circuit design, the IA realizes a very high power-supply rejection ratio (PSRR), and can be operated at signal supply voltage in the rage between 2.5 and 5.5 V. It was fabricated using 0.5um double-poly triple-metal CMOS technology, and occupies a die area of 0.2mm2.The amplifier provides a gain of 40 dB and has high common-mode rejection ration (CMRR) better than 100 dB. The IA has a power consumption of 160uW operating from a 3.3 V power supply

Amplifiers in Biomedical Engineering: A Review from Application Perspectives

Continuous monitoring and treatment of various diseases with biomedical technologies and wearable electronics has become significantly important. The healthcare area is an important, evolving field that, among other things, requires electronic and micro-electromechanical technologies. Designed circuits and smart devices can lead to reduced hospitalization time and hospitals equipped with high-quality equipment. Some of these devices can also be implanted inside the body. Recently, various implanted electronic devices for monitoring and diagnosing diseases have been presented. These instruments require communication links through wireless technologies. In the transmitters of these devices, power amplifiers are the most important components and their performance plays important roles. This paper is devoted to collecting and providing a comprehensive review on the various designed implanted amplifiers for advanced biomedical applications. The reported amplifiers vary with respect to the class/type of amplifier, implemented CMOS technology, frequency band, output power, and the overall efficiency of the designs. The purpose of the authors is to provide a general view of the available solutions, and any researcher can obtain suitable circuit designs that can be selected for their problem by reading this survey

A Novel Low Noise High Gain CMOS Instrumentation Amplifier for Biomedical Applications

This work describes a novel technique of designing a low noise high gain CMOS instrumentation amplifier for biomedical applications. A three op-amp instrumentation amplifier have been designed by employing two simple op-amps at the two inputs and a folded cascode op-amp at the output. Both input and output stage op-amps are 2-stage. Most of the earlier designed op-amp in literature uses same type of op-amp at the input and output stages of instrumentation amplifier. By using folded cascode two stage op-amp at the output, we have achieved significant improvement in gain and CMRR. Transistors sizing plays a vital role in achieving high gain and CMRR. To achieve a desirable gain, common mode rejection ratio and other performance metrics, selection of most appropriate op-amp circuit topologies & optimum transistor sizing was the main criteria for design of instrumentation amplifier for biomedical applications. The instrumentation amplifier is simulated using Cadence Spectre tool and layout is designed in Cadence Layout editor at 0.18µm CMOS technology. Each of the input op-amp provides a gain and CMRR of 45dB and 72dB respectively. The output stage folded cascode amplifier provides a gain of 82dB and a CMRR of 92dB. The design achieves an overall gain and CMRR of 67dB and 92db respectively. The designed instrumentation amplifier consumes only 263µW of power suitable for biomedical signal processing applications.DOI:http://dx.doi.org/10.11591/ijece.v3i4.317

An Energy-Efficient Bridge-to-Digital Converter for Implantable Pressure Monitoring Systems

This paper presents an energy-efficient, duty-cycled, and spinning excitation bridge-to-digital converter (BDC) designed for implantable pressure sensing systems. The circuit provides the measure of the pulmonary artery pressure that is particularly relevant for the monitoring of heart failure and pulmonary hypertension patients. The BDC is made of a piezoresistive pressure sensor and a readout integrated circuit (IC) that comprises an instrumentation amplifier (IA) followed by an analog-to-digital converter (ADC). The proposed design spins both the bridge excitation and the ADC’s sampling input voltages simultaneously and exploits duty cycling to reduce the static power consumption of the bridge sensor and IA while cancelling the IA’s offset and 1/f noise at the same time. The readout IC has been designed and fabricated in a standard 180-nm CMOS process and achieves 8.4 effective number of bits (ENOB) at 1 kHz sampling rate while drawing 0.53 µA current from a 1.2 V supply. The BDC, built with the readout IC and a differential pressure sensor having 5 kΩ bridge resistances, achieves 0.44 mmHg resolution in a 270 mmHg pressure range at 1 ms conversion time. The current consumption of the bridge sensor by employing duty cycling is reduced by 99.8% thus becoming 0.39 µA from a 1.2 V supply. The total conversion energy of the pressure sensing system is 1.1 nJ, and achieves a figure-of-merit (FoM) of 3.3 pJ/conversion, which both represent the state of the art

Low-Noise Micro-Power Amplifiers for Biosignal Acquisition

There are many different types of biopotential signals, such as action potentials (APs), local field potentials (LFPs), electromyography (EMG), electrocardiogram (ECG), electroencephalogram (EEG), etc. Nerve action potentials play an important role for the analysis of human cognition, such as perception, memory, language, emotions, and motor control. EMGs provide vital information about the patients which allow clinicians to diagnose and treat many neuromuscular diseases, which could result in muscle paralysis, motor problems, etc. EEGs is critical in diagnosing epilepsy, sleep disorders, as well as brain tumors. Biopotential signals are very weak, which requires the biopotential amplifier to exhibit low input-referred noise. For example, EEGs have amplitudes from 1 μV [microvolt] to 100 μV [microvolt] with much of the energy in the sub-Hz [hertz] to 100 Hz [hertz] band. APs have amplitudes up to 500 μV [microvolt] with much of the energy in the 100 Hz [hertz] to 7 kHz [hertz] band. In wearable/implantable systems, the low-power operation of the biopotential amplifier is critical to avoid thermal damage to surrounding tissues, preserve long battery life, and enable wirelessly-delivered or harvested energy supply. For an ideal thermal-noise-limited amplifier, the amplifier power is inversely proportional to the input-referred noise of the amplifier. Therefore, there is a noise-power trade-off which must be well-balanced by the designers. In this work I propose novel amplifier topologies, which are able to significantly improve the noise-power efficiency by increasing the effective transconductance at a given current. In order to reject the DC offsets generated at the tissue-electrode interface, energy-efficient techniques are employed to create a low-frequency high-pass cutoff. The noise contribution of the high-pass cutoff circuitry is minimized by using power-efficient configurations, and optimizing the biasing and dimension of the devices. Sufficient common-mode rejection ratio (CMRR) and power supply rejection ratio (PSRR) are achieved to suppress common-mode interferences and power supply noises. Our design are fabricated in standard CMOS processes. The amplifiers’ performance are measured on the bench, and also demonstrated with biopotential recordings

Advanced sensors technology survey

This project assesses the state-of-the-art in advanced or 'smart' sensors technology for NASA Life Sciences research applications with an emphasis on those sensors with potential applications on the space station freedom (SSF). The objectives are: (1) to conduct literature reviews on relevant advanced sensor technology; (2) to interview various scientists and engineers in industry, academia, and government who are knowledgeable on this topic; (3) to provide viewpoints and opinions regarding the potential applications of this technology on the SSF; and (4) to provide summary charts of relevant technologies and centers where these technologies are being developed

Wireless Telemetry System for Implantable Sensors

Advanced testing of medical treatments involves experimentation on small laboratory animals, such as genetically modified mice. These subjects are used to help researchers develop medication and cures for humans. To understand the effects of the treatments, innovative telemetry systems are developed, that enable remote real-time cardiac monitoring. The latest research in the field of cardiac monitoring has revealed two major limitations with wireless implantable systems: a) the current size of implantable electronics limits the physical size of the system to larger subjects; and b) the systems only interface with one sensor type (e.g., pressure sensor only). This research focuses on the design of a wireless telemetry system architecture, intended to retrieve blood pressure and volume data. A physical prototype is created that is 2.475 cm3 and weights 4.01 g. This thesis will enable a path towards miniaturization, leading to the incorporation of a wireless system into small laboratory animals