Arrayed pH-responsive microvalves controlled by multiphase laminar flow

In chemical and biological assays, the synchronized control of multiple valves is very important. Currently there is no control scheme for the use of a large number of valves without adopting bulky peripheral control devices such as pumps or electrical equipment. Therefore, we propose a simple pH-responsive microvalve array system and a new multiplexing technology that, through its reliance on multiphase laminar flow, facilitates the operation of arrayed multiple microvalves. For the fabrication of the microvalve arrays, we have used pH-responsive hydrogel microspheres produced by a microfluidic chip. By incorporating these microspheres inside an arrayed microvalve polydimethylsiloxane (PDMS) platform, we produced pH-responsive arrayed microvalves with 'open' and 'close' operations carried out by the multiphase laminar streams of pH solutions. The constructed arrayed microvalves were adequately controlled by the multiphase pH buffer; the pressure of the pH-buffer solutions controlled the widths of the sample flow. Based on the simplicity and reliability of the operating principles, this new arrayed-valve system will decrease the need for complicated peripheral lines and will remove the need for many solenoid valves, which are currently used for the individual control of arrayed valves.