Label-Free Optical pH Measurement Based on Chitosan-TEOS-PDMS Hydrogel Layer for Microfluidic Applications

The optical pH sensor based on smart hydrogel material was designed for use in microfluidic applications. The chitosan-tetraethyl orthosilicate (chitosan-TEOS) interpenetrating network was synthesized as a pH-sensitive part of the sensor. This chitosan-TEOS-PDMS layer was bonded by oxygen plasma treatment to a thin layer of polydimethylsiloxane (PDMS), which enabled easily integrating of the sensor layer into the microfluidic chips. Also, the thickness of this PDMS layer worked as an adjustable parameter to control the sensitivity of the sensor. In addition, the optical astigmatism method (the method used in CD/DVD optical pickup unit) was utilized to measure the pH-induced variations of the sensor layer by monitoring the laser beam profile on a charge-coupled device (CCD). The experimental results showed that the fabricated sensor responded to pH changes and became stable in less than 90 s. It showed a sensitivity of 54 and 94 pixel/pH using the spin-coated PDMS thickness of 75 and 28 $\mu \text{m}$ , respectively.

[1]  A. Bonyár,et al.  PDMS Bonding Technologies for Microfluidic Applications: A Review , 2021, Biosensors.

[2]  Sang Heon Lee,et al.  Astigmatism-based displacement sensor powered by deep neural networks , 2021 .

[3]  Chern Yang Leong,et al.  Hydrogel based Fabry-Pérot cavity for a pH sensor. , 2020, Optics express.

[4]  Esra Ermis,et al.  A combined 3D printing/CNC micro-milling method to fabricate a large-scale microfluidic device with the small size 3D architectures: an application for tumor spheroid production , 2020, Scientific Reports.

[5]  O. Wolfbeis,et al.  Optical Sensing and Imaging of pH Values: Spectroscopies, Materials, and Applications , 2020, Chemical reviews.

[6]  G. Urban,et al.  Zero-consumption Clark-type microsensor for oxygen monitoring in cell culture and organ-on-chip systems , 2020 .

[7]  K. Choi,et al.  A lung cancer-on-chip platform with integrated biosensors for physiological monitoring and toxicity assessment , 2020 .

[8]  Md. Shahruzzaman,et al.  Chitosan based bioactive materials in tissue engineering applications-A review , 2020, Bioactive materials.

[9]  P. Wild,et al.  A fluorescence-based pH sensor with microfluidic mixing and fiber optic detection for wide range pH measurements , 2019, Sensors and Actuators A: Physical.

[10]  M. Shafiq,et al.  In vitro study of chitosan-based multi-responsive hydrogels as drug release vehicles: a preclinical study , 2019, RSC advances.

[11]  M. Vellekoop,et al.  Microfluidic oxygen sensor system as a tool to monitor the metabolism of mammalian cells , 2019, Sensors and Actuators B: Chemical.

[12]  G. Minas,et al.  Cost-Efective Lab-on-a-Chip Device for Seawater pH Quantification by Optical Methods , 2019, 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII).

[13]  Peng Zhang,et al.  Microfluidic platforms for cell cultures and investigations , 2019, Microelectronic Engineering.

[14]  Yuanyuan Xu,et al.  The crossing and integration between microfluidic technology and 3D printing for organ-on-chips. , 2018, Journal of materials chemistry. B.

[15]  Z. Bai,et al.  Focusing error detection based on astigmatic method with a double cylindrical lens group , 2018, Optics & Laser Technology.

[16]  Anja Boisen,et al.  Hacking CD/DVD/Blu-ray for Biosensing , 2018, ACS sensors.

[17]  Yong Zhao,et al.  Smart hydrogel-based optical fiber SPR sensor for pH measurements , 2018 .

[18]  Francesca Stradolini,et al.  Organs-on-chip monitoring: sensors and other strategies , 2018 .

[19]  Hwu.  Hacking CD / DVD / Blu-ray for Biosensing , 2018 .

[20]  W. Cai,et al.  Optical sensing properties of Au nanoparticle/hydrogel composite microbeads using droplet microfluidics , 2017, Nanotechnology.

[21]  Y. Rakovich,et al.  Immobilization of pH-sensitive CdTe Quantum Dots in a Poly(acrylate) Hydrogel for Microfluidic Applications , 2017, Nanoscale Research Letters.

[22]  Ning Hu,et al.  Multisensor-integrated organs-on-chips platform for automated and continual in situ monitoring of organoid behaviors , 2017, Proceedings of the National Academy of Sciences.

[23]  L. Tayebi,et al.  Wound dressing application of pH-sensitive carbon dots/chitosan hydrogel , 2017 .

[24]  David J. Mooney,et al.  Designing hydrogels for controlled drug delivery. , 2016, Nature reviews. Materials.

[25]  O. N. Oliveira,et al.  Silica-based photonic crystals embedded in a chitosan-TEOS matrix: preparation, properties and proposed applications , 2016, Journal of Materials Science.

[26]  Yaopeng Zhang,et al.  Integrated microfluidic device for the spherical hydrogel pH sensor fabrication , 2016 .

[27]  D. Narmoneva,et al.  Modulation of cell function by electric field: a high-resolution analysis , 2015, Journal of The Royal Society Interface.

[28]  K. Draget,et al.  Chitosan: Gels and Interfacial Properties , 2015 .

[29]  Yanyan Tang,et al.  Label-free study of the function of ion channel protein on a microfluidic optical sensor integrated with artificial cell membrane. , 2014, Lab on a chip.

[30]  H. Shivakumar,et al.  Investigation of Swelling Behavior and Mechanical Properties of a pH-Sensitive Superporous Hydrogel Composite , 2012, Iranian journal of pharmaceutical research : IJPR.

[31]  D. Marshall,et al.  Microfluidics for single cell analysis. , 2012, Current opinion in biotechnology.

[32]  Devendra Kumar,et al.  Removal of toxic metals using superabsorbent polyelectrolytic hydrogels , 2011 .

[33]  Fumihito Arai,et al.  Photoprocessible Hydrogel Microsensor for Local Environment Measurement on a Microfluidic Chip , 2011, IEEE/ASME Transactions on Mechatronics.

[34]  Jens Lienig,et al.  Review on Hydrogel-based pH Sensors and Microsensors , 2008, Sensors.

[35]  R. Funk,et al.  Effects of Electromagnetic Fields on Cells: Physiological and Therapeutical Approaches and Molecular Mechanisms of Interaction , 2006, Cells Tissues Organs.

[36]  A. Manz,et al.  Lab-on-a-chip: microfluidics in drug discovery , 2006, Nature Reviews Drug Discovery.

[37]  Jeff Blyth,et al.  pH-sensitive holographic sensors. , 2003, Analytical chemistry.

[38]  S. Haam,et al.  A novel pH-sensitive membrane from chitosan--TEOS IPN; preparation and its drug permeation characteristics. , 2001, Biomaterials.

[39]  Sanford A. Asher,et al.  Photonic Crystal Chemical Sensors: pH and Ionic Strength , 2000 .

[40]  G. Jobst,et al.  Integrated optical pH sensor using replicated chirped grating coupler sensor chips , 1998 .

[41]  D K Cohen,et al.  Automatic focus control: the astigmatic lens approach. , 1984, Applied optics.