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Page 4 of 15 Duan et al. Soft Sci. 2025, 5, 4 https://dx.doi.org/10.20517/ss.2024.46

bladder monitoring is achieved when the device is used by the user [Figure 1D]. The system employs BIA to
monitor and automatically analyze bladder capacity non-invasively and in real time by current conduction,
after applying a weak alternating current (usually 50 kHz) to the surface area of the bladder [28,29] . This is
achieved by using a sensor to measure the voltage change as the current passes through the human bladder,
which allows for the collection of information on the change in electrical impedance of the bladder. This
information is then communicated wirelessly with the user interface (UI) (mobile phone app). Figure 1E
depicts a live view of the user wearing the smart device on the abdomen. Supplementary Table 1 shows a
comparison of conventional and development equipment in terms of dimensions.

This fully integrated biocompatible electronics for real-time monitoring and intelligent assessment of
human bladder impedance employs a non-invasive methodology to provide real-time, continuous bladder
filling information. It is portable and user-friendly, facilitating patient understanding of their needs. By
anticipating the time of urination, the electronics enable patients or their family members to prepare in
advance and reduce the likelihood of embarrassing instances of involuntary urination. In instances where
medical science has yet to develop a cure for urination disorders, the human bladder impedance
measurement smart device, developed using biocompatible electrode synthesis, BIA and multi-module
system integration technology, enhances the patient’s control over the time of bladder emptying and
reduces the patient’s psychological pressure, thereby improving the quality of life.

EXPERIMENTAL
Materials and instruments
Chitosan (C H NO , MW = 100,000), acetic acid solution (CH COOH, MW = 60.05), sodium hydroxide
4n
3
11n
6n
standard solution (NaOH, 0.1 mol/L), potassium hydroxide (KOH, MW = 60.05, 95%), magnesium chloride
(MgCl , 99%, MW = 95.21), glucan (C H O , MW = 1,500) and deionized water were supplied by Macklin
6n
10n
5n
2
Biochemical Co., Ltd., Shanghai, China. Ethanol (C H OH, 95%) and potassium chloride (KCl, MW =
2
5
74.55) were purchased from Sinopharm Chemical Reagent Co., Ltd., Shanghai, China. Urea (H NCONH ,
2
2
99.0%) was obtained from Tianjin Third Chemical Plant Co., Ltd., Tianjin, China. Ascorbic acid (C H O ,
6
8
6
MW = 176.13) was obtained from Yatai United Chemical Co., Ltd., Wuxi, China. The KEWLAB analytical
balance was purchased from Qiulai Technology Co., Ltd., Hangzhou, China. Benchtop magnetic stirrer
(model SC-MS-II) and benchtop homogenizer (model KW-4BC) were purchased from Cedex Electronics
Co., Ltd., Beijing, China. The electric heating blast drying oven (model DHG-9145A) was obtained from
Yiheng Scientific Instrument Co., Ltd., Shanghai, China. The Series 7 force gauge was purchased from
MARK-10 Corporation, USA. The Autolab electrochemical workstation (model Nova2) was purchased
from Metrohm Autolab B.V. through Maiqiang Technology Co., Ltd., Shanghai, China.
Design and performance study of patch electrodes
Patch electrode sensing is a non-invasive electrophysiological measurement for the assessment of bladder
capacity. Its design is based on the conductive and capacitive response of biological tissues to electrical
currents [1,30] . The system employs a two-electrode configuration, comprising a working electrode (WE) and
a counter electrode (CE). The CE injects low-frequency alternating current (LFAC) into the human bladder,
while the WE serves as a receiver electrode, collecting information about the bladder variable. This variable
is generated due to the conductivity and capacitance of the bladder tissues in response to the current. Given
the necessity for direct contact between the patch electrode and the human skin and the potential for long-
term monitoring of bladder impedance, it is essential that the electrode exhibits good biocompatibility, anti-
stretching properties, selectivity, and durability. This is to prevent the occurrence of undesirable reactions,
such as allergies and inflammation, that may arise due to prolonged contact [31-33] . In light of these
considerations, chitosan was selected as the primary material for the flexible substrate of the electrode.
Chitosan is a natural polymer material with a strong affinity for human cells. It exhibits excellent properties,