Hongjie Hu

Options for the continuous and non-invasive monitoring of blood pressure are limited. Cuff-based sphygmomanometers are widely available, yet provide only discrete measurements. The clinical gold-standard approach for the continuous monitoring of blood pressure requires an arterial line, which is too invasive for routine use. Wearable ultrasound for the continuous and non-invasive monitoring of blood pressure promises to elevate the quality of patient care, yet the isolated sonographic windows in the most advanced prototypes can lead to inaccurate or error-prone measurements, and the safety and performance of these devices have not been thoroughly evaluated. Here we describe validation studies, conducted during daily activities at home, in the outpatient clinic, in the cardiac catheterization laboratory and in the intensive care unit, of the safety and performance of a wearable ultrasound sensor for blood pressure monitoring. The sensor has closely connected sonographic windows and a backing layer that improves the sensor’s accuracy and reliability to meet the highest requirements of clinical standards. The validation results support the clinical use of the sensor.

Wearable electromyography devices can detect muscular activity for health monitoring and body motion tracking, but this approach is limited by weak and stochastic signals with a low spatial resolution. Alternatively, echomyography can detect muscle movement using ultrasound waves, but typically relies on complex transducer arrays, which are bulky, have high power consumption and can limit user mobility. Here we report a fully integrated wearable echomyography system that consists of a customized single transducer, a wireless circuit for data processing and an on-board battery for power. The system can be attached to the skin and provides accurate long-term wireless monitoring of muscles. To illustrate its capabilities, we use this system to detect the activity of the diaphragm, which allows the recognition of different breathing modes. We also develop a deep learning algorithm to correlate the single-transducer radio-frequency data from forearm muscles with hand gestures to accurately and continuously track 13 hand joints with a mean error of only 7.9°.

Accurate and continuous monitoring of cerebral blood flow is valuable for clinical neurocritical care and fundamental neurovascular research. Transcranial Doppler (TCD) ultrasonography is a widely used non-invasive method for evaluating cerebral blood flow¹, but the conventional rigid design severely limits the measurement accuracy of the complex three-dimensional (3D) vascular networks and the practicality for prolonged recording². Here we report a conformal ultrasound patch for hands-free volumetric imaging and continuous monitoring of cerebral blood flow. The 2 MHz ultrasound waves reduce the attenuation and phase aberration caused by the skull, and the copper mesh shielding layer provides conformal contact to the skin while improving the signal-to-noise ratio by 5 dB. Ultrafast ultrasound imaging based on diverging waves can accurately render the circle of Willis in 3D and minimize human errors during examinations. Focused ultrasound waves allow the recording of blood flow spectra at selected locations continuously. The high accuracy of the conformal ultrasound patch was confirmed in comparison with a conventional TCD probe on 36 participants, showing a mean difference and standard deviation of difference as −1.51 ± 4.34 cm s⁻¹, −0.84 ± 3.06 cm s⁻¹ and −0.50 ± 2.55 cm s⁻¹ for peak systolic velocity, mean flow velocity, and end diastolic velocity, respectively. The measurement success rate was 70.6%, compared with 75.3% for a conventional TCD probe. Furthermore, we demonstrate continuous blood flow spectra during different interventions and identify cascades of intracranial B waves during drowsiness within 4 h of recording.

The weight of conventional photovoltaic (PV) solar panels is a significant challenge in applications that can benefit from the integration of this renewable energy source, but are sensitive to increased weight loads. Numerous commercial buildings and auxiliary structures are designed with little to no spare structural capacity. Vehicle fuel efficiency is directly tied to the total vehicle weight. Lightweight modules can address this challenge by reducing weight, enabling PV elements to be installed or retrofitted at low cost for parking roofs, in building structures (Building Integrated PV or BIPV), and in vehicles (Vehicle Integrated PV VIPV). The main challenge in acheiving lightweight PV modules is replacing the glass frontsheet while maintaining transparency, mechanical stability and weatherability over the lifetime of the module. Transparent Tedlar® PVF films have been used for decades in protecting graphics and signage and photovoltaic backsheets. Building on years of successful field performance, a new transparent Tedlar® TFS15BM3 film has been designed to provide a high level of outdoor UV stability and protection, offering a significantly lighter technologically advanced alternative to traditional glass. In this paper, we present the performance of this film as a protective frontsheet of solar modules. The unique balance of durability, UV resistance, high level of light transmittance, lasting UV protection, mechanical toughness, chemical resistance, good adhesion to encapsulant, easy cleaning, light weight and flexibility makes this an attractive alternative to traditional glass in applications necessitating lightweight.

Ultrasound adds the third dimension to wearable sensors.