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Cheng et al. Soft Sci. 2026, 6, 36 Page 5 of 15

nitrogen purging) to eliminate dissolved oxygen. Subsequently, the mixture was stirred at 500 r/min for 24 h
at 25 °C. Then, 25 mM of AIBN was added, and another three cycles of degassing were performed to
maintain an inert atmosphere and prevent side oxidations, particularly decarboxylation. The reaction vessel
was then placed in a 40 °C water bath and continuously stirred at 500 r/min for 5 h to initiate radical
polymerization and form the polypyrrole shell on the NiHCF nanocube core, obtaining the NiHCF-MIP
(BE) sample. In addition, a non-imprinted polypyrrole (NIP) shell-coated sample (NiHCF-NIP NCs) was
also prepared for contrast. This sample was synthesized without the addition of cortisol molecules during
polymerization.

After polymerization, the centrifugation-collected product was immersed in 5 mL of an acetic acid/methanol
mixture (volume ratio 7:3), followed by stirring at 500 r/min for 12 h to effectively remove the target
molecule and generate the cortisol molecular imprinting cavities. The extracted material was washed with
deionized water three times and with methanol once. Finally, the purified core-shell NiHCF-MIP NCs were
dried under vacuum at 30 °C for 12 h, yielding the cortisol-sensing material. In the following text, unless
otherwise stated, NiHCF-MIP denotes samples that have undergone the elution process and possess cortisol
cavities.

Preparation of carbon cloth coated with NiHCF-MIP NCs
To preliminarily evaluate the sensing performance of NiHCF-MIP NCs, 5 mg of NiHCF-MIP NCs were
dissolved in 3 mL of anhydrous ethanol and ultrasonicated for 5 minutes to achieve uniform dispersion.
Next, 50 μL of the dispersion was drop-cast onto a 1 cm × 1 cm commercial carbon cloth and allowed to dry.
This drop-casting procedure was repeated three times. The prepared carbon cloth was employed as the
working electrode for electrochemical testing in a threeelectrode system.

Preparation of spinning solution
The spinning solution consists of DMF as the solvent, PAN and TPU as hydrophilic thermoplastic polymers,
poloxamer F127 as a dispersing agent, MWCNTs as a conductive additive , and core-shell NiHCF-MIP
[25]
NCs as the cortisol-sensing active material. These solid components (NiHCF-MIP NCs, MWCNTs, PAN,
TPU, and F127) are in a mass ratio of (3-12):10:300:100:100. The total solid mass to DMF volume ratio
ranges from 5.13 to 5.22 g per 20 mL.

To prepare the solution, PAN, F127, and TPU were first dissolved in DMF under continuous stirring at
40 °C for 2 h, yielding a colorless, transparent, and viscous solution. MWCNTs were then introduced into
this solution and stirred at 40 °C for an additional 2 h. Next, NiHCF-MIP NCs were added and stirred at the
same temperature for 1 h to achieve uniform distribution throughout the polymer matrix. Finally, the
mixture was ultrasonicated at 300 W for 1 h to remove entrapped air bubbles, yielding a stable and
homogeneous spinning solution.

Preparation of coaxial cortisol-sensing yarns
The cortisol-sensing yarn was fabricated via conjugate electrospinning. In this process, a conductive carbon
thread was positioned at the center as the core yarn. A nanofiber layer consisting of NiHCF-MIP NCs was
wrapped around the conductive carbon thread to form a coaxial structure [Figure 1B]. A 5 mL syringe
equipped with a 20 G needle was used. The two spinnerets were set to voltages of +12.5 and -12.5 kV,
respectively, and were aligned 15 cm apart, directly facing the center of the rotating collecting horn at a
distance of 10 cm. During conjugate electrospinning, the micro-pump feeding rate was maintained at
1-3 mL/h, the collecting horn rotated at 100-200 r/min, the diameter of the take-up roll was 4.78 cm, and its
rotational speed was 0.8 r/min. The production rate per hour is calculated using Equation 1: