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Page 4 of 19 Hussain et al. Soft Sci. 2025, 5, 21 https://dx.doi.org/10.20517/ss.2025.02

Preparation of wearable photonic array biosensor films
Scheme 1A illustrates the sequential fabrication of circular CLCN-IPN biosensor films. First, microscopic
glass slides were cut into 4 cm pieces, cleaned with water and ethanol, and dried using an air blower. Clean
polyethylene terephthalate (PET) films were adhered to the glass slides using double-sided tape. The PET
films were then washed with water and ethanol, followed by drying with an air blower, and referred to as the
“bottom glass slide”. Both the bottom and top glass slides underwent surface functionalization. They were
treated in an oxygen plasma cleaner (PC-002-CE, USA) connected to a vacuum pump (MM71A4, Valtaro
Motori, Italy) for 15 min. After oxygen plasma treatment, the top glass slide was functionalized with a
PFOTS mixture by placing it in a sealed petri dish containing FPOTS mixture and heating at 70 °C for 5 h.
Meanwhile, the bottom glass slide was coated with a TMSPMA mixture using a spin coater (Laurell Tech
Corporation, USA) at 2,000 rpm for 1 min, followed by baking at 65 °C for 5 h. Both slides were then
assembled using a 20 µm thick plastic spacer, creating a 20 µm gap between them. This gap was filled with
the reactive cholesteric liquid crystal (CLC) mixture (composition provided in Supplementary Table 1 of the
supporting information) via capillary forces. Once infiltration was complete, the assembly was exposed to
ultraviolet (UV) photopolymerization for 20 min using a UV lamp (DR-301C, China). After
polymerization, the top glass slide was removed, leaving the CLCN film fixed to the bottom glass slide. The
CLCN film was thoroughly washed with acetone to remove any nonreactive 5CB. Next, a hydrogel
monomer mixture (composition provided in the supporting information in Supplementary Table 2) was
applied to the surface of the CLCN film and allowed to infiltrate for 30 min. The film was then exposed to
UV curing for 30 min to establish a stable IPN. The glass slide and double-sided tape were removed from
the flexible CLCN-IPN film, which remained adhered to the PET substrate. The flexible film was cut into
5 mm diameter circular shapes using a laser cutter (Beambox, Flux, Taipei, Taiwan) and the Beam Studio
software. To immobilize enzymes on the CLCN-IPN circular films, the films were treated with an EDC/
NHS mixture [1 M EDC-HCl and 2 M NHS mixed at a 1:1 (v/v) ratio] in a glass vial for 2 h. After
activation, the films were wiped with tissue paper and proceeded for enzyme immobilization. The
concentrations and types of enzymes used are detailed in the corresponding sections. After enzyme
immobilization, the circular CLCN-IPN films were washed with deionized (DI) water and prepared for
sensing applications. The color shift in the CLCN-IPN biosensor films corresponds to the concentration of
the target analyte. Scheme 1B describes the preparation of the soft wearable device. A mold was initially
created using a SIGA MAX UV 3D printer (NSW, Australia). The PDMS precursor was prepared by mixing
Sylgard 184 silicone elastomer base and curing agent at a 9:1 (w/w) ratio. The PDMS precursor was then
poured into the resin mold, covered with a polymethylmethacrylate (PMMA) hard sheet, and baked at
60 °C for 24 h. Once cured, a uniform patterned PDMS layer with clear microchannels was peeled off from
the mold. The circular CLCN-IPN biosensor films were then placed into the reservoirs of the patterned
PDMS layer (details provided in Section “Urea detection by circular photonic CLCN-IPN biosensor film”).
The fabricated wearable photonic array biosensor was stored at -8 °C in a refrigerator.

Preparation of artificial sweat
Artificial sweat was prepared based on a previously reported method. The components included sodium
lactate (20 mM), D-glucose (0.5 mM), sodium chloride (80 mM), potassium chloride (9 mM), calcium
chloride (1 mM), urea (21 mM), iron (II) chloride (0.01 mM), and magnesium chloride hexahydrate
(0.3 mM), all dissolved in a buffer solution at pH 6. Varying concentrations of glucose, urea, or lactate were
achieved by adjusting the corresponding component while maintaining the concentrations of the other
ingredients constant.

Off-body and on-body sweat analysis
For off-body sweat analysis, a syringe pump (WPI, 230, Germany) was used. A round PDMS layer with a
diameter of 35 mm was fabricated, and a hole was punched in its center to connect it to the syringe pump