Continuous wireless pressure monitoring and mapping with ultra-small passive sensors for health monitoring and critical care

Abstract

Continuous monitoring of internal physiological parameters is essential for critical care patients, but currently can only be practically achieved via tethered solutions. Here we report a wireless, real-time pressure monitoring system with passive, flexible, millimetre-scale sensors, scaled down to unprecedented dimensions of 1 Â 1 Â 0.1 cubic millimeters. This level of dimensional scaling is enabled by novel sensor design and detection schemes, which overcome the operating frequency limits of traditional strategies and exhibit insensitivity to lossy tissue environments. We demonstrate the use of this system to capture human pulse waveforms wirelessly in real time as well as to monitor in vivo intracranial pressure continuously in proof-of-concept mice studies using sensors down to 2.5 Â 2.5 Â 0.1 cubic millimeters. We further introduce printable wireless sensor arrays and show their use in real-time spatial pressure mapping. Looking forward, this technology has broader applications in continuous wireless monitoring of multiple physiological parameters for biomedical research and patient care.

Polyurethane foam coated with a multi-walled carbon nanotube/polyaniline nanocomposite for a skin-like stretchable array of multi-functional sensors

“…The sensitivity is a normalized change in resistance, ðR NH3 À R 0 Þ=R 0 × 100(%) upon exposure to NH 3 gas, where R NH3 and R 0 are the resistance with and without NH 3 gas, respectively. The selectivity of the sensor was measured at room temperature with the two environmentally toxic gases NH 3 and NO 2 at the same concentration (25 p.p.m.). As is clearly shown in Figure 5d, higher sensitivity to NH 3 was observed.…”

Recent Progress in Electronic Skin

“…Effective signal transduction that converts external stimuli into an analog electronic signal is an important component of accurate quantitative monitoring. Traditional transduction methods (e.g., piezoresistivity,13 capacitance,14 and piezoelectricity15 are widely used in different types of sensors, and other transduction methods (e.g., optics, wireless antennas, and triboelectricity) are undergoing rapid development to meet new challenges and opportunities that will broaden the applications of e‐skin to robotics, prosthesis, and human–machine interaction 16. The details of selected methods are presented in this section.…”

A microscale optical implant for continuous in vivo monitoring of intraocular pressure

“…Moreover, the area of the core optomechanical cavity is 0.283 mm 2 (600 μm in diameter) occupying only 44% of the entire sensor area and suggesting further miniaturization. This compact size is an order of magnitude smaller than the state-of-the-art research devices 46,62,63 and three orders of magnitude smaller than commercially available sensors 65 . For IOP monitoring, the sensor is implanted into the eye where its deformable SiN membrane is exposed to the IOP and interrogated using the broadband invisible NIR regime (800-1100 nm) of a tungsten light bulb (Figure 1f) (see in vivo testing below for details on the sensor implantation).…”

“…Such measurements can only be obtained for up to 24 h because of side complications that accompany long-term use [41][42][43] . To overcome the aforementioned limitations, implants based on radio-frequency (RF) technologies have been used to monitor endovascular pressure 44 , intracranial pressure (ICP) 45,46 , and IOP [47][48][49][50][51][52][53][54][55][56][57][58] . The typical size of these implants ranges from a millimeter to a few centimetres.…”