Laser fabrication of Ti stent and facile MEMS flow sensor integration for implantable respiration monitoring

TL;DR

This work tackles the need for reliable respiration monitoring in preclinical animal studies by integrating a MEMS-based calorimetric airflow sensor with a biocompatible Ti stent. A fiber-laser kirigami/origami approach fabricates a 50 µm Ti stent, while a MEMS sensor on a 7.5 µm PI film with a $50^ circumf C$ heater provides real-time flow measurement via differential heating. Calibrations reveal a TCR of $2{,}677$ ppm/$^\u00b0C$ and a linear airflow response, demonstrated in an airway-mimicking tube and validated in a proof-of-concept ventilator setup, showing bidirectional flow detection and a tidal volume near $10 ext{ mL}$ per cycle. The study offers a viable path toward enhanced preclinical respiratory assessments through integrated, implantable MEMS sensing, with clear future directions toward in vivo testing, mucus/inflammation considerations, and wireless power/data solutions for clinical translation.

Abstract

Animal experiments play a vital role in drug discovery and development by providing essential data on a drug's efficacy, safety, and physiological effects before advancing to human clinical trials. In this study, we propose a stent-based flow sensor designed to measure airflow in the airways of laboratory animals. The stent was fabricated from biocompatible Ti using a combination of fiber laser digital processing and an origami-inspired folding technique. The sensing structure was developed through standard micro-electromechanical systems (MEMS) microfabrication technology. To integrate the sensing structure with the metallic stent, a facile insertion process was employed, where the sensor film was positioned at the stent's center using its natural buckling mechanism. Once fabricated, the stent implant was expanded and installed within an airway-mimicking tube to validate its functionality. A proof-of-concept trial using an artificial ventilator successfully demonstrated real-time respiration monitoring, confirming the feasibility of the proposed system for airflow measurement in preclinical studies. This stent-based sensor offers a promising approach for enhancing respiratory assessments in laboratory animals, potentially improving the accuracy of drug evaluations and respiratory disease research.

Figures (10)

• Figure 1: Respiration airflow sensing using thermal calorimetry. (a) Micrograph of the fabricated MEMS thermal flow sensing structure. Sensing mechanism using heat distribution around the sensing structure in the (a) absence and (b) presence of airflow.
• Figure 2: Externally installed heater actuation circuit.
• Figure 3: Laser ablated Ti foil with variable laser power of (a) 8 W, (b) 10 W, (c) 12 W, and (d) 14 W; variable laser scanning speed of (e) 50 mm/s, (f) 20 mm/s, (g) 10 mm/s, and (h) 5 mm/s; variable laser emission frequency of (i) 50 kHz, (j) 25 kHz, (k) 10 kHz, and (l) 5 kHz. Scale bars are of 1 mm length. Scale bars of the inset micrographs are of 10 µ m length.
• Figure 4: Planar Ti stent structure.
• Figure 5: Sensor integration through a facile insertion process.