Assistant Professor Vanderbilt University Nashville, Tennessee, United States
Introduction: Sensing the mucus conditions of the airway is vital for diagnosing lung diseases and monitoring airway health when implantable devices such as stents are in place. However, current methods, reliant on bronchoscope inspection, lack the ability to provide continuous real-time feedback in a prolonged time. Here, we introduce artificial cilia equipped with sensory capabilities to detect mucus conditions, including viscosity and level which are crucial biomarkers for disease diagnosis. Our method leverages external magnetic fields to actuate the cilia for viscosity sensing, while the sensor’s shape-sensing ability further enhances mucus assessment. Additionally, mucus level sensing is achieved through capacitance measurement, offering self-calibration and adjustable sensitivity and range, enabled by external magnetic fields. To enable prolonged and wireless data access, we integrate Bluetooth Low Energy communication and onboard power. We validate our method by deploying the sensor independently or in conjunction with an airway stent within a trachea phantom and ovine trachea ex vivo. This advancement empowers real-time monitoring of mucus conditions, facilitating early disease detection and providing stent patency alerts. Our method promises to elevate patient outcomes and enhance quality of life by ensuring timely interventions and personalized care.
Materials and
Methods: As shown in Fig. 1A, we propose a cilia-inspired sensory device for sensing airway mucus conditions, which has onboard sensors, data processing and transmission units, and power module. Figure 1A shows that the device could be integrated with an airway stent for continuously monitoring the advanced mucus conditions such as viscosity and layer thickness inside the human central airway which are important biomarkers for disease diagnosis and stent patency. In addition to the on-board components, an external magnetic field easily generated by a light-weight wearable system plays a key role in enabling the advanced sensing functions.
On one hand, Figure 1B illustrates the mechanism for sensing mucus viscosity. The viscosity sensor, inspired by biological cilium, is made of magnetic composite, which could beat inside the liquid upon applying a rotating magnetic field. Integrating artificial cilia in airway stents have demonstrated mucus transportation by fluid-structure interaction but sensing mucus property is still limited. The envelope of its motion is larger when the sensor is beating in a less viscous fluid when actuating with the same rotating magnetic field. Consequently, the fluid viscosity can be interpreted from deformation of the artificial cilium, which could be estimated by integrating a strain-gauge sensor, when the deformation can be obtained by measuring the sensor electrical resistance (Fig. 1C). On the other hand, Figure 1D-E shows the mucus level sensor and the mechanism of sensing mucus layer thickness using a capacitor-based sensor. Figure 1F-H demonstrate the wireless electronics and Figure I-J show the user interface.
Results, Conclusions, and Discussions: In summary, our research has culminated in the development of an innovative airway stent equipped with integrated artificial cilia. These cilia possess the remarkable ability to sense various mucus conditions, including viscosity, thickness, and temperature, thereby holding promise for monitoring stent patency. Our viscosity sensor operates on the principle of an artificial cilium actuated by an external magnetic field, while a flexible strain gauge sensor measures the curvature of the cilium. For mucus thickness sensing, we employ a capacitor that can be tilted by an external magnetic field for self-calibration. Furthermore, temperature data is captured using an onboard sensor. The artificial cilium sensors are activated by wearable magnetic actuation systems, facilitating real-time monitoring of lung physiology and mucus properties. By continuously gathering data on mucus viscosity, quantity, and other pertinent parameters, these sensors furnish invaluable insights for patients fitted with airway stents.
In the future, we will develop customized wireless electronics to scale down the electronic circuits and chips for wireless communication. We will also integrate wireless charging unit for remote powering of the stent. The resilience of the circuit could be further improved by developing liquid metal elastomer. Multimodal sensors merging temperature sensor, color sensor, and hydration sensor could be integrated to allow multi-modal sensing of the mucus properties. This continuous monitoring allows for early detection of changes in mucus properties or the onset of complications, facilitating timely interventions and personalized treatment plans. By closely monitoring mucus properties and airway health, medical practitioners can tailor treatment strategies to each patient’s unique needs, optimizing therapeutic outcomes and preventing disease exacerbations.
