A shape memory alloy microvalve with flow sensing

Matthew E. Piccini, Bruce C. Towe

Research output: Contribution to journalArticle

32 Scopus citations

Abstract

A Nitinol™ actuated silicone tubing microvalve is combined with a downstream thermocouple forming an integrated system for the control and metering of microliter volumes. The integrated device is of a normally closed design having a break pressure of more than 68.9 kPa (517 mmHg), dimensions on the order of 1 mm × 2 mm × 2 mm, inert fluid contact surfaces, and senses flow. Power pulses of 213 mW are required for 2.5 s response times. Opening of the valve is brought about by a temperature induced metallurgical transition of a short piece of nitinol wire with a diameter of 75 μm. The force generated by the transition is harnessed in order to stretch microbore silicone tubing away from a luminal plug (synthetic ruby ball), thus forming flow channels. Actuation is performed using a pulsed paradigm with a distinctive on and off period enabling flow sensing capabilities. The integrated thermal principle flow sensor operates by sensing the peak temperature derivative of a transient thermal pulse in the flow stream imparted by joule heating of the nitinol wire when actuated. It was found that this flow sensing scheme proved to be a reliable method of detecting valve performance changes over time. The system is constructed using readily available commercial components including microbore silicone tubing, nitinol shape memory alloy (SMA) wire, a miniature synthetic ruby ball, and a thermocouple.

Original languageEnglish (US)
Pages (from-to)344-349
Number of pages6
JournalSensors and Actuators, A: Physical
Volume128
Issue number2
DOIs
StatePublished - Apr 19 2006

Keywords

  • Flow sensor
  • Microfluidic
  • Microvalve
  • Shape memory alloy

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Instrumentation
  • Condensed Matter Physics
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Electrical and Electronic Engineering

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