Monitoring Wound Health through Bandages with Passive LC Resonant Sensors

Abstract

This paper details a passive, inductor–capacitor (LC) resonant sensor embedded in a commercial dressing for low-cost, contact-free monitoring of a wound; this would enable tracking of the healing process while keeping the site closed and sterile. Spiral LC resonators were fabricated from flexible, copper-coated polyimide and interrogated using external reader antennas connected to a two-port vector network analyzer; the forward transmission scattering parameter (S21) magnitude was collected, and the resonant frequency (MHz) and the peak-to-peak amplitude of the resonant feature were identified. These increase during the healing process as the permittivity and conductivity of the tissue change. The sensor was first tested on gelatin-based tissue-mimicking phantoms that simulate layers of muscle, blood, fat, and skin at varying phases of wound healing. Finite element modeling was also used to verify the empirical results based on the expected variations in dielectric properties of the tissue. The performance of the resonant sensors for in vivo applications was investigated by conducting animal studies using canine patients that presented with a natural wound as well as a controlled cohort of rat models with surgically administered wounds. Finally, transfer functions are presented that relate the resonant frequency to wound size using an exponential model (R 2 = 0.58–0.96). The next steps in sensor design and fabrication as well as the reading platform to achieve the goal of a universal calibration curve are then discussed.

Multifunctional Dressing for Wound Diagnosis and Rehabilitation

“…[75] In addition to electrochemical and resistive detection approaches, there are some wearable sensors based on capacitive, electromagnetic, and resonant sensing methods. [76][77][78] Charkhabi et al [79] embedded a inductor-capacitor (LC) resonant [48] Copyright 2019, Wiley-VCH GmbH. b) Visible color changes of PAN-Eu CPs15% mats with different concentrations of H 2 O 2 and on the wound under the ultraviolet condition.…”

“…d) Illustration of the resonant sensor system consisting of an LC sensor and an external 2-loop reader antenna for wound health monitoring. Reproduced with permission [79]. Copyright 2021, American Chemical Society.…”

A Review of Recent Advances in Flexible Wearable Sensors for Wound Detection Based on Optical and Electrical Sensing

“…While the above applications involve sensitive materials in electrical monitoring, initiatory analyses have found that the dielectric properties of wound tissues are relevant to the trabecular evolution process. Charkhabi et al [ 142 ] used the wound region as a self-capacitance medium to reflect the state of the wound with the help of a passive LC resonant circuit. During the healing process, the monitoring parameters such as the amplitude of the scattering parameter S 21 and the resonance frequency gradually rose.…”

Intelligent Wearable Sensors Interconnected with Advanced Wound Dressing Bandages for Contactless Chronic Skin Monitoring: Artificial Intelligence for Predicting Tissue Regeneration

“…In recent decades, intelligent wearable sensors with human-machine interfaces have gathered keen research interest for their potential to revolutionize modern medical technologies with the real-time feature to examine physiological cues of the human body. , Wireless electronics elicited great promise for real-time data acquisition of vital signs of human health, body motion movement, and signal transmission of emergency requests and furthered a new field of advanced wound monitoring. − Currently, complex chronic wounds represent a tremendous challenge to modern healthcare providers as they affect around 2% of the world population with a high cost of medical care worldwide . Generally, the wound healing process undergoes different stages, including hemostasis, inflammation, proliferation, and remodeling .…”