An integrated microfluidic chip enabling control and spatially resolved monitoring of temperature in micro flow reactors

Abstract

A strength of microfluidic chip laboratories is the rapid heat transfer that, in principle, enables a very homogeneous temperature distribution in chemical processes. In order to exploit this potential, we present an integrated chip system where the temperature is precisely controlled and monitored at the microfluidic channel level. This is realized by integration of a luminescent temperature sensor layer into the fluidic structure together with inkjet-printed micro heating elements. This allows steering of the temperature at the microchannel level and monitoring of the reaction progress simultaneously. A fabrication procedure is presented that allows for straightforward integration of thin polymer layers with optical sensing functionality in microchannels of glass-polydimethylsiloxane (PDMS) chips of only 150 μm width and 29 μm height. Sensor layers consisting of polyacrylonitrile and a temperature-sensitive ruthenium tris-phenanthroline probe with film thicknesses of about 0.5 to 6 μm were generated by combining blade coating and abrasion techniques. Optimal coating procedures were developed and evaluated. The chip-integrated sensor layers were calibrated and investigated with respect to stability, reproducibility, and response times. These microchips allowed observation of temperature in a wide range with a signal change of around 1.6 % per K and a maximum resolution of around 0.07 K. The device is employed to study temperature-controlled continuous micro flow reactions. This is demonstrated exemplarily for the tryptic cleavage of coumarin-modified peptides via fluorescence detection.

Optofluidic Device Based Microflow Cytometers for Particle/Cell Detection: A Review

“…Hoera et al . utilized a CCD camera for fluorescence imaging of temperature and reaction process in a microfluidic chip reactor [ 75 ]. Yang et al conducted an experiment at a flow rate of 10 µL/h to allow CCD cameras to capture the accurate images for real-time cell separation in a microflow cytometer [ 72 ].…”

Integration and application of optical chemical sensors in microbioreactors

“…So having a way to monitor the temperature is very important also in microfluidic systems. Hoera et al 97 presented sensor layers made of polyacrylonitrile and a temperature sensitive ruthenium tris phanthroline probe with a thickness of only 0.5-6 μm capable of monitoring temperatures from 25 to 70°C. Zhou et al 31 presented PDMS stained with ZnO particles (quantum dots) for a whole chip temperature measurement.…”

Optimization of Temperature Sensing with Polymer-Embedded Luminescent Ru(II) Complexes

“…Among the various temperature-dependent optical properties that can be used to develop a temperature optode (optical sensor), luminescence thermometry, encompassing fluorescence, and phosphorescence, is probably the most sensitive and versatile technique [4], as it shows particular advantages. Firstly, it provides unbeatable spatial resolution, down to intracellular temperature sensing [5,6]; it can also be used for imaging temperature gradients [7,8] and it allows for simultaneous monitoring of temperature and other (chemical) parameters [9,10]. Moreover, luminescence lifetime measurements offer the advantages of being immune to the material photodegradation, indicator leaching, excitation source or detector aging, and to fiber-optic bending.…”