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

Abstract 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. 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. The capsule prototype has dimensions of ø 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. The experimental results indicate that the proposed capsule can achieve Bluetooth remote-triggered liquid sampling in the digestive tract and satisfy the clinical requirements.