Development of a Portable, Spring-based, and Non-electric Syringe Pump for Microfluidic Device Operation

Abstract

We developed a syringe pump powered by a spring mechanism. It doesn't require any external power source during operation. Flow control is achieved by adjusting the gear teeth ratio connected to the spring. The spring maintains a constant angular velocity, resulting in linear movement of the rack gear and syringe. The pump can operate for more than 50 minutes without a decrease in flow rate over time. The Micro Droplet Generator utilizes a needle and tubing connector. By employing multiple pumps with different flow rates, microdroplet generation can achieve oil-to-water ratios ranging from 1:30 to 1:315. This system allows for flexible utilization in confined spaces like biosafety cabinets or radiation shielding boxes, as it doesn't rely on a power supply line and is not affected by the surrounding environment. To produce injectable radioactive 131I-HAMA microgels, a portable infusion pump-based approach was used, ensuring immediate therapeutic use with minimal radiation loss. The efficacy of these radioactive hydrogel microdroplets in treating HeLa cells was confirmed using the spring pump and droplet generator. In response to the limitations of the previous pump design, which had a maximum operation time of one hour and lacked flow rate adjustment during operation, a follow-up study was conducted. To extend the operation time, mainsprings, serving as power sources, were stacked, and holders were added to the escapement mechanism within each mainspring to prevent simultaneous unwinding. When the upper mainspring rotates beyond a certain angle, it sequentially activates the lower mainspring by disengaging from the holder that locks the escapement wheel. This sequential mainspring operation mechanism increased the operating time to three hours using a triple-structured spring. The capability of maintaining a constant flow rate over time was demonstrated by implementing gradient flow using two syringe pumps running for three hours.