Structure Design and Experimental Study on a Shape Memory Alloy based Negative Pressure Sampling Capsule

Purpose: This study aims to introduce a wireless, remotely triggered biopsy capsule based on shape memory alloy(SMA). This capsule utilizes the negative pressure suction principle to achieve liquid sampling within the digestive tract. Methods: The proposed capsule is designed with an SMA spring-driven sampling trigger mechanism. An external magnetic field directs the capsule to the sampling area and aligns the sampling port with the sampling liquid. A Bluetooth signal is then sent and energizes the SMA spring, causing deformation and generating negative pressure for liquid sampling. Results: The capsule prototype has dimensions of ϕ 15.0 mm × 30.0 mm. Both simulation and in-vitro experiments have been carried out. Results showed that the proposed capsule has a rapid response time of 1.4 s and can sample liquids with viscosities ranging from 0.7 mPa⋅s to 100 mPa⋅s with the maximum sampling volume around 0.2 mL. Furthermore, the capsule's sealing performance has also been verified. Conclusion: The experimental results indicate that the proposed capsule can achieve Bluetooth remote-triggered liquid sampling in the digestive tract and satisfy the clinical requirements.