# A Sensitive Thermoelectric Respiratory Sensor Using a Hollow‐Square Structure of Cubic Silicon Carbide‐Based Heterojunction

## TL;DR

A new self-powered respiratory sensor using silicon carbide improves sensitivity and durability for monitoring breathing in hot environments.

## Contribution

A hollow-square cubic silicon carbide heterojunction sensor with enhanced thermal voltage output for respiratory monitoring.

## Key findings

- The hollow-square design increases thermal voltage output by 3.5 times compared to conventional structures.
- The sensor maintains stable performance across 1000 airflow cycles and functions effectively in high-temperature environments.
- Integration into a functional mask enables real-time respiratory rate monitoring and alerts for workers in hot conditions.

## Abstract

Respiratory rates play a crucial role in health assessment and rehabilitation. However, current respiratory monitoring devices often rely on metal‐ or polymer‐based sensors, and skin‐mounted electronics, face challenges such as low sensitivity, limited durability/stability, and substantial power demands in complex respiratory environments. Herein, we introduce innovations in design and fabrication of a hollow‐square cubic silicon carbide (3C‐SiC)‐based self‐powered sensor, which operates via the Seebeck effect in 3C‐SiC/Si heterojunction, for respiratory rate monitoring. Through manipulating thermal transport, this design significantly enhances airflow sensing performance, yielding a thermal voltage output approximately 3.5 times higher than that of conventional solid structures. The sensor exhibits remarkable repeatability and durability, maintaining stable voltage responses across 1000 airflow testing cycles. Moreover, elevated temperatures drive a transition from conventional Seebeck effect in a single semiconductor layer to heterojunction‐driven effects, resulting in a higher thermal voltage and enabling further sensor optimization under high‐temperature environments. By integrating this hollow‐square 3C‐SiC sensor into a functional mask, the sensor enables real‐time monitoring respiratory rate of workers in hot environments. An integrated alarm system provides alerts to the users in response to sudden changes in their respiratory rates, offering a reliable and practical tool for continuous health surveillance of workers in high‐temperature environments.

A sensitive self‐powered respiratory sensor is developed using a hollow‐window structure implemented on a 3C‐SiC/Si heterojunction‐based platform. This design enables the manipulation of thermal transport with the heterojunction regulating the flow of thermally generated charge carriers, yielding a significantly higher output thermal voltage than that of conventional designs.