This paper presents a sub–0.1-mm ³ , fully integrated, injectable ultrasonic wireless device for biomedical temperature sensing.

Piezoelectric Micromachined Ultrasonic Transducers (PMUT) and Capacitive Micromachined Ultrasonic Transducers (CMUT) have seen great developments in recent years, both in terms of performance and scope of applications within the biomedical ultrasound domain. This paper presents a review of the state-of-the-art of PMUT and CMUT technologies, focusing on their principle of operation, microfabrication techniques and use in different biomedical imaging and therapeutic applications. The advantages and drawbacks of PMUT and CMUT technologies in comparison with conventional bulk transducers are highlighted, the trade-offs among PMUTs and CMUTs are discussed, and their relevance in the current landscape of medical diagnostics and therapeutic uses is outlined, thus providing a clear overview of these promising technologies for the present and the next generation biomedical ultrasound applications.

Emerging non-imaging ultrasound applications, such as ultrasonic wireless power delivery to implantable devices and ultrasound neuromodulation, require wearable form factors, millisecond-range pulse durations and focal spot diameters approaching 100 μm with electronic control of its three-dimensional location. None of these are compatible with typical handheld linear array ultrasound imaging probes. In this work, we present a 4 mm × 5 mm 2D ultrasound phased array transmitter with integrated piezoelectric ultrasound transducers on complementary metal-oxide-semiconductor (CMOS) integrated circuits, featuring pixel-level pitch-matched transmit beamforming circuits which support arbitrary pulse duration. Our direct integration method enabled up to 10 MHz ultrasound arrays in a patch form-factor, leading to focal spot diameter of ∼200 μm, while pixel pitch-matched beamforming allowed for precise three-dimensional positioning of the ultrasound focal spot. Our device has the potential to provide a high-spatial resolution and wearable interface to both powering of highly-miniaturized implantable devices and ultrasound neuromodulation.

In this work an alternative neuroscience tool for electromagnetic measurements of neurons at the level of individual cells is developed. To perform such measurements we propose the integration of an array of magnetoresistive sensors on micro-machined Si probes capable of being inserted within the brain without further damage. Si-etch based micromachining process for neural probes is demonstrated in the manufacture of a probe with 15 magnetoresistive sensors in the tip of each shaft. Magnetic tunnel junction sensors with dimensions of 30 μm × 2 μm, sensitivities of 3.32 V/T and detectivity of ≈13 nT/Sqrt (Hz) are placed in the end of the sharply defined probe tips. In order to measure the small signals coming from the neurons, a homemade signal amplifying system was used with a noise level of 240 n V_RMS for the system bandwidth. The full system noise is 2772 n V_RMS.

Bovine mastitis is the most costly disease for dairy farmers and the most frequent reason for the use of antibiotics in dairy cattle; thus, control measures to detect and prevent mastitis are crucial for dairy farm sustainability. The aim of this study was to develop and validate a sensitive method to magnetically detect Streptococcus agalactiae (a Group B streptococci) and Streptococcus uberis in raw milk samples. Mastitic milk samples were collected aseptically from 44 cows with subclinical mastitis, from 11 Portuguese dairy farms. Forty-six quarter milk samples were selected based on bacterial identification by conventional microbiology. All samples were submitted to PCR analysis. In parallel, these milk samples were mixed with a solution combining specific antibodies and magnetic nanoparticles, to be analyzed using a lab-on-a-chip magnetoresistive cytometer, with microfluidic sample handling. This paper describes a point of care methodology used for detection of bacteria, including analysis of false positive/negative results. This immunological recognition was able to detect bacterial presence in samples spiked above 100 cfu/mL, independently of antibody and targeted bacteria used in this work. Using PCR as a reference, this method correctly identified 73% of positive samples for streptococci species with an anti-S. agalactiae antibody, and 41% of positive samples for an anti-GB streptococci antibody.

The development of giant magnetoresistive (GMR) sensors has demonstrated significant advantages in nanomedicine, particularly for ultrasensitive point-of-care diagnostics. To this end, the detection system is required to be compact, portable, and low power consuming at the same time that a maximum signal to noise ratio is maintained. This paper reports a CMOS front-end with integrated magnetoresistive sensors for biomolecular recognition detection applications. Based on the characterization of the GMR sensor's signal and noise, CMOS building blocks (i.e., current source, multiplexers, and preamplifier) were designed targeting a negligible noise when compared with the GMR sensor's noise and a low power consumption. The CMOS front-end was fabricated using AMS 0.35 μm technology and the magnetoresistive sensors were post-fabricated on top of the CMOS chip with high yield (97.9%). Due to its low circuit noise (16 nV/√Hz) and over all equivalent magnetic noise (11.5 nT/√Hz), the full system was able to detect 250 nm magnetic nanoparticles with a circuit imposed signal-to-noise ratio degradation of only -1.4 dB. Furthermore, the low power consumption (6.5 mW) and small dimensions (7.59 mm²) of the presented solution guarantees the portability of the detection system allowing its usage at the point-of-care.