Evaluation of Microvalves Developed for Point-of-Care Testing Devices Using Shape-Memory Polymers

Abstract

A temporal change in temperature in an actuating shape-memory polymer (SMP) valve has been measured by analyzing the fluorescence spectrum of sulforhodamine B in the aqueous solution. The SMP microvalve used in this study was recently developed by the authors. It is actuated by the shape recovery of poly( -caprolactone) (PCL), which is triggered by heat from a microheater. To obtain information about temperature rise during operation, we measured "temperature quenching" of the fluorescence from sulforhodamine B using laser-induced fluorescence (LIF) spectroscopy. The maximum temperature during valve actuation was approximately 60 °C and was slightly higher than the phase transition temperature 52 °C of the PCL material used in this study. The results indicate that the present microvalve is potentially applicable to practical point-of-care testing devices.

Microfluidic Model for Optical Detection of Nanoparticles in Whole Blood

“…The ratiometry of fluorescence intensity between two different wavelengths was performed to eliminate dependencies related to tracer concentration, excitation laser power, and optical density of blood. Two different wavelengths of 582 nm and 617 nm were selected for their large difference in the fluorescence quantum yield dependence on the temperature [24,25]. A low concentration of sulforhodamine B solution (0.01%, w/w) in phosphate-buffered saline (PBS) (Wako Pure Chemical Industries Ltd., Japan) and whole blood (anticoagulated with heparin-sodium, Biopredict International, France) were prepared as sample solutions containing a temperature sensitive dye.…”

Shape-memory surfaces for cell mechanobiology

“…Since then, many researchers have tried to introduce biocompatibility and biodegradability into SMPs for various biomedical applications which has led to substantially improved health care, such as implantable devices or minimally invasive surgical procedures without damaging the surrounding tissues/organs. In addition, SMPs have also presented additional potential in the area of micro-electro-mechanical systems (MEMS), actuators, self-healing, unique adhesion devices and cell culture platforms [ 27 – 29 ]. Because the surface morphology is of fundamental important to many surface-related material properties, recent studies started to use SMPs as substrates to form topography with tunable property, namely shape-memory surfaces (SMSs).…”

Implementation of poly(ε-caprolactone) sheet-based shape-memory polymer microvalves into plastic-based microfluidic devices

“…To fulfill the requirements of a microfluidic valve for practical use in disposable integrated microfluidic devices, we proposed and developed a shape-memory polymer (SMP) microvalve that uses the solid-solid phase transition of poly(ε-caprolactone) (PCL). 19,20) The SMP microvalves connect or disconnect two adjacent microchannels formed on a separate substrate by the thermally triggered recovery of the PCL surface structure that was memorized in advance. Since the prestored energy in the PCL is used for valve actuation, peripheral systems for operating SMP microvalves can be made compact, unlike the case of pneumatic microvalves, which usually require relatively large and elaborate equipment or facilities to supply and control the compressed air.…”