Microvalves are useful components for several microfluidic applications in which they control the fluid flow in a microfluidic system. Most microvalves to date are made by using silicon micro-machining, which is a complex manufacturing process, or soft lithography using Polydimethylsiloxane (PDMS) which has a high gas permeability. Next to that most microvalves in literature have small actuation forces resulting in small pressure ranges and large leakages at low pressure levels. In this paper, a normally open microvalve which is fabricated by only using 3D printing techniques with a bio-compatible resin is presented, making it more easy and accessible to manufacture. The novelty is the integrated micro-channels, membrane and microfluidic connections in a single 3D printed piece. The utilized actuator is a commercially available piezo stack, which has a displacement of 34 µm at 150V. Due to its large actuation force the microvalve can modulate fluids from -600 to 600 mbar, with measured flow-rate levels between 0-90 µl/min and projected flow-rate levels between 0-410 µl/min. In fully closed state the leakage-rate of the microvalve is 1.67 µl/min at 600 mbar, with a static power consumption of 442.5 mW. Subsequently it is shown that after using higher clamping torques (> 0.7 Nm) the microvalve can operate leakage free up to 1.5 bar. Additionally a 3-to-1 fluid selector is designed using three microvalves, which can be integrated into a portable microfluidic platform for Organ-on-Chip (OoC) applications.

An Organ-on-a-Chip (OoC) is a microfluidic device that mimics an organ function on a chip. The goal of the OoC technology is to create disease models of various organs and use them to minimise animal testing. One of the important parameters to maintain the cells/tissues on the OoC is the temperature, typically at 37 °C. Usually, cell culture incubators are used to maintain the temperature of cells on the OoC. However, it is inconvenient for external flow control instrumentation to interface with OoC inside the incubator, and other temperatures being not possible. Therefore, an on-chip temperature controller is needed. In this report, a temperature control system for an OoC is designed, implemented and tested. To cover a wide temperature range, multiple peltier elements are chosen to confine the temperature control only at the region close to cell chambers in the OoC. A resistive temperature detector (RTD) is used as feedback to control the temperature by a proportional-integral-derivative (PID) controller. To avoid any heat loss beyond the Organ-on-a-Chip, a 3D-printed polylactic acid (PLA) holder with good thermal insulating properties is used. The holder is designed for four chips to accommodate control chips along with test chips. A dedicated PCB with control electronics is designed and implemented to control the temperature on all four chips powered by a battery. A temperature uniformity of +/- 0.7 °C of 19 mm at 68 μL/min and 23 mm at 10 μL/min along a total microfluidic channel length of 40 mm (from inlet to outlet), a width of 5 mm, and a depth of 0.3 mm before compression, was achieved. The response time to recover from changes in the temperature is approximately 2 minutes. With a power consumption of 0.84 Watts per chip to maintain 37 °C, four chips can function on a 20000 mAh battery for a minimum of 4.5 hours (only cooling at a minimum of 18 °C) and a maximum of 8.3 hours (only heating at 37 °C) before recharge. The temperature control system was tested on Hepatocytes and Cholangiocytes for liver-on-a-chip applications, which showed that the oxygen disappearance rate is 9.87 times faster when maintained at 37 °C compared to room temperature.

Due to the developments of microfluidics, Organ-On-Chip (OOC) technology is developing rapidly in recent years. Microflow plays a vital role in OOC applications, thus a microfluidic platform that can generate high-quality flow is always needed. However, the existing OOC systems contain bulky peripheral components, incompact design and low-quality fluid flow (bubbles and fluctuations). To deal with these issues, a portable and integrated OOC flow control platform system has been developed. The platform is designed for three kinds of popular Organ-On-Chip models: Lung-On-Chip, Gut-On-Chip and Tissue-On-Chip,and is able to change the fluid (both liquid and gas) automatically and control their flow rate on the chip. The fluid actuation is based on a stable vacuum tank and therefore can create high-quality flow without fluctuations. PID flow controllers are used to maintain the desired flow rate under a constant pressure difference created by the vacuum pump. By integrating with other predetermined off-the-shelf components with small footprints, the platform realized is 290mm long, 240mm wide and 220mm tall, and weighs 4.8 kg in total. The system is highly modular with capability to exchange the necessary components, and can be placed under the optical microscope (upright or inverted) to monitor inside the microfludic chip without having to disconnect. It can also be placed inside an incubator for continuous controlled fluid flow in the OOC. The system works on a rechargeable battery that can be easily changed to support long-term cell culture. The setup consumes a minimum of 7.2W and a maximum of 11.5W power.