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Zhong et al. Soft Sci. 2025, 5, 3 https://dx.doi.org/10.20517/ss.2024.52 Page 9 of 15

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measurement range, is 1.6 × 10 dB/kPa. The results demonstrated that the maximum pressure level for the
sensor was determined to be 275 kPa [Supplementary Figure 10A, Supplementary Movie 3]. During impact
tests, we found that the DCLS sensor exhibits high insensitivity to external mechanical stress, indicating its
ability to withstand potential collisions or impacts during use.

To evaluate the temperature drift characteristics of the DCLS sensor, we placed the sensor in a constant
temperature chamber for testing. During the experiment, the temperature was increased by 5 °C every
30 min, and the changes in light intensity of red and blue light were recorded in detail. The experimental
results show that the temperature drift trends of red and blue lights are highly consistent. Through linear
fitting analysis, it is found that the change rates of red and blue light intensity are 0.0141/°C and 0.0142/°C
[Supplementary Figure 10B]. This study conducted a series of experiments and data analyses on the
performance of the DCLS sensor, revealing its exceptional stability and durability. However, there are some
issues that need attention. For example, as the ambient temperature increases, the attenuation of red and
blue lights in the light guide medium slightly intensifies. This phenomenon may be attributed to the
characteristics of the flexible materials used - as the temperature rises, the difference in refractive index
between the cladding and the light guide medium decreases, causing more light to leak out. To address this,
future research could consider using light guide medium with higher refractive indices, such as
polyurethane, and black silicone with lower refractive indices to further reduce the impact of temperature
variations.

DCLS sensor for soft robotic applications
Currently, there are few flexible sensors that are calibration-free. Therefore, we fabricated three distinct
types of soft robots: a fruit sorting robot, a fish-inspired robot, and a hand orthotic exoskeleton robot, which
were integrated with the DCLS sensor to demonstrate this characteristic. The study protocol was approved
by the Medical Ethics Committee from the Department of Psychology and Behavioral Sciences, Zhejiang
University, China (reference number: [2022]098), and informed consent was obtained from all participants.

Automatic fruit classification robots play a crucial role in agriculture by enhancing sorting efficiency and
[42]
significantly reducing labor costs . As illustrated in Figure 4A, we designed a pneumatic grasping robot
equipped with the DCLS sensor to grasp target fruits. The details of the design and fabrication can be found
in Supplementary Text 6 and Supplementary Figure 11. The robot comprises three pneumatic networks
(pneu-nets) actuators, each housing an airway and seamlessly integrating a DCLS sensor. The upper
segment of the pneu-nets actuator serves as an air chamber, while the lower section is sealed with a DCLS
sensor through an integrated casting method. The pneu-nets actuators can conform to the external fruit
surface when bent, facilitating efficient manipulation. Upon installation of the DCLS sensor on the robot,
recalibration is not required to detect the external surface curvatures of the robot’s pneu-nets actuator. This
capability assists the soft robot in discerning fruit sizes, thereby enabling rapid sorting decisions. Figure 4B
illustrates the sorting process of such a soft robot. Notably, the absorbance difference between the red and
blue layers exhibits an almost linear correlation with the curvature of fruit surfaces, inversely proportional
to the size of ordinary oranges. According to the curvature measured by the DCLS sensors, the fruit size can
be promptly recognized and then sorted using a threshold judgment [Supplementary Movie 4].

The fish-inspired robot serves as a pivotal tool in deep-sea exploration [43,44] . Accurate detection of the tail’s
swing angle is imperative for precise control of this robot. As shown in Figure 5A, a fish-inspired robot
featuring multiple spines was crafted, incorporating the seamless integration of a DCLS sensor within these
structural elements. The details of the design and fabrication can be found in Supplementary Text 6. Within
the fish body, provisions were made to securely house essential components such as the battery, servo