## 4 Microfluidic Dye-Sensitized Solar Cells Fabrication and Tests Conditions  
The PDMS-free prototypes of \(\upmu\)DSSC were fabricated by a laser ablation technique using a commercially available system (Versa Laser VLS 2.30, Universal Laser System Inc., Scottsdale, AZ, USA) equipped with a 30 W CO\({}_{2}\) (wavelength 10.6 \(\upmu\)m) pulsed laser source and a high-power density focusing optic (HPDFO). The system was used for cutting through, drilling, and engraving construction materials: glass substrates, adhesive film layers, and PMMA sheets. The schematic drawing of the cell assembly is shown in Figure 11b. The device consists of five layers: the photoaode with a fluorine-doped tin oxide (FTO) layer (4) and the silver highly conductive paths (5), the adhesive film layer (2) of 120 \(\upmu\)m thickness (7955 MI, the acrylic adhesive 200 MP 3 M, St. Paul, MN, USA), the conductive (FTO) glass counter electrode (3) with the silver highly conductive paths (5), the adhesive film layer (2) of 120 \(\upmu\)m thickness, and the PMMA made base (1) of 3 mm thickness. The polyethylene tubing 1.09/0.38 mm (OD/ID) was glued into holes after folding the layers.  
The fabricated DSSCs were of n-type configuration, whose operation principles were presented in Figure 5. The conductive glass substrates TCO13-15 (15 \(\Omega\)/sq) of 1.3 mm thickness, coated on one side with fluorine-doped tin oxide, were purchased from Sola-ronix (Switzerland). Before applying functional layers, the glass substrates were cleaned in deionized water in an ultrasonic bath and rinsed in isopropanol. The low electrically resistive silver paths were prepared on the FTO surfaces using a silver glass frit paste Elcosil SG/SP (Solaronix, Switzerland). The photoaode active layer of 1.5-2.0 \(\upmu\)m thick was prepared onto the FTO glass substrate using nano-TiO\({}_{2}\) precursor Ti-Nanoxide T600/SC-the anatase particles of dia. 15-20 nm suspension (Solaronix, Switzerland) and stained for 72 h by soaking after firing in the anhydrous ethanol solution (0.5 mM) of Ruthenium-based and organic dyes mixture (1:1 mol): N719 (Rutheniumer 535-bis-TBA, CAS: 207347-46-4), and SQ2 (5-carboxy-2-[[3-(2,3-dihydro-1,1-dimethyl-3-ethyl-1H-benzo[e]indol-2-ylidene)methyl]-2-hydroxy-4-oxo-2-cyclobuten-1-ylidene)methyl]-3,3-dimethyl-1-octyl-3H-indiolium) (Solaronix, Switzerland). Sensitized photoaode was washed in isopropanol and dried at room temperature. The counter electrode was prepared on the FTO glass substrates by the deposition of a thin layer of nano-Pt catalyst Platisol T (Solaronix, Switzerland). Each thin layer was deposited onto the substrate using a spin coater (Laurell Technologies, North Wales, PA, USA) according to the standard procedures recommended by the reagent  
Figure 11: The \(\upmu\)DSSC with the serpentine microchannel: (**a**) The photography of the cell; (**b**) Schematic drawing of the cell: (1) PMMA made base with fluid tubes connection ports; (2) Adhesive film layers; (3) Counter electrode with nano-Pt layer; (4) Photoaode with dye-sensitized nano-TiO\({}_{2}\) layer; (5) Conductive silver paths.  
supplier. The fabricated prototype of uDSSC with the serpentine microchannel is shown in Figure 11a.  
The acetonitrile-based low viscosity electrolyte with redox couple iodide/tri-iodide (30 mM acetonitrile solution) with additives of ionic liquid, lithium salt, pyridine derivative, and thiocyanate: Iodolyte HI-30 (Solaronix, Switzerland) was used in the experiments. Ionic and electrical conductivity measurements were carried out at room temperature using Voltcraft multimeters (Conrad Electronic, Switzerland). DC Electrical Load Rigol DL3021 (China) was used to obtain the I-V curve. The microfluidic DSSC was examined at room temperature and lighting conditions of LED 100 mW/cm\({}^{2}\) with CRI > 95, using the led reflector WIFI 100B (Fomei, Czech Republic) as a light source.