(H-318) Flow Regulator for Stable Output Flow in Connection with Elastomeric Pumps

Introduction:: Precise and controlled drug delivery is crucial for the safety and efficacy of continuous infusion systems used for drug treatment, anesthesia, cancer treatment, diabetes treatment, and pain management^1-4 Two types of pumps, electronic and non-electronic, are used in these systems. The elastomeric pump is a type of non-electronic pump that has a simple design and is more affordable than the electronic pump. However, the generated pressure by elastomeric pumps is often unstable, resulting in low injection accuracy compared to electronic pumps⁵. Therefore, a flow rate regulator capable of stabilizing the output flow rate is required. Previous flow regulators can be classified as active or passive types. Among them, passive regulators can adjust the output flow rate by self-deforming the internal structure tailored to the input pressure without the need for additional active devices^{6, 7}. We propose a new flow regulator that can be fabricated through a simple, low-cost fabrication method and can control the output flow rate by a self-adjustable deformable membrane in response to input pressure. The device consists of an open-end microchannel, a closed-end microchannel (no outlet), and a flexible membrane in the middle. Because of the double-layer structure, a pressure difference occurs between the two channels when fluid flows. The membrane is deformed by the pressure difference, the channel structure is changed. As a result, the hydraulic resistance is changed. Therefore, it can maintain a stable output flow rate over a target pressure range without the need for additional equipment.


Materials and Methods:: KMPR1025, polydimethylsiloxane elastomer kit (PDMS, Sylgard 184), and Microscope slides were purchased from MicroChem, Dow Corning (Midland, MI, USA), and LK LAB KOREA, respectively.

The device fabrication process involved creating a master mold using photolithography with KMPR1025 on a silicon wafer. The wafer was coated with KMPR and exposed to UV light through a photomask, post-exposure baked, and immersed in TMAH aqueous alkaline developer for pattern development. To make microchannels, PDMS was spin-coated onto the mold and cured at 80 ℃ for 30 min before being detached and bonded onto a glass slide. Finally, two microchannels were bonded to each other after O₂ plasma treatment to seal the device.

We conducted the following experiments to verify the flow rate controllability of the regulator in an elastomeric pump system. First, the elastomeric pump (M20-O, Neofuser, S&SMED Co., Korea) filled with saline solution was connected to the inlet of the regulator. At this time, a pressure gauge was connected between the pump and the regulator to measure the supply pressure of the pump. The outlet of the regulator was connected to the reservoir placed on an electric balance. Then, the output flow rate was measured every 10 minutes with the electric balance.


Results, Conclusions, and Discussions:: We developed two types of flow regulators: the straight type and the diaphragm type. We evaluated the output flow rate controllability of the flow regulator depending on the design (height, width, diaphragm location, and diaphragm diameter) of the regulator. The target pressure range is determined to be between 400 and 500 mbar whose range is mainly used for pain relief¹.

Each device was found to have a non-linear increase in output flow rate as the inlet pressure increased. We experimentally verified that the output flow rate at the target supply pressure varied depending on the design of the device, and the flow rate variation was stable within 9%. Through this, it was confirmed that adjusting the device dimensions allows for output at the desired flow rate.

Finally, we assessed the practicality of the flow regulator in an actual drug infusion system by testing the flow rate controllability of the regulator when connected to an elastomeric pump. The average input pressure from the pump was recorded at 41.91 kPa with a maximum deviation of 28.7%. While the existing pump system had a maximum deviation of 29.87% in output flow rate without the flow regulator connection, the maximum deviation decreased to 13.16% and 13.81% respectively when straight type with a height of 50 µm and width of 500 µm, and diaphragm type with a height of 50 µm, width of 500 µm and diaphragm with diameter of 3.0 mm was located in the middle of the channel devices were connected. By incorporating the flow regulator, the output flow rate deviation was reduced by approximately 45%. Since commercial elastomeric pumps have flow rate deviations of up to 15%, an elastomeric pump with the present flow regulator can be clinically acceptable8. We confirmed that the flow regulator has flow controllability in a clinical setup. Therefore, we believe that our device can provide a new route for drug infusion systems that can achieve on-demand therapeutic efficacy.


Acknowledgements (Optional): : This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government(MSIT) (NRF-2021R1A2C1009326, RS-2023-00207801)


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