| Author: | Ma, Kit Ming |
| Title: | Wearable flexible healthcare devices-pressure sensation technology and photobiomodulation |
| Advisors: | Tao, Xiao Ming (SFT) |
| Degree: | Ph.D. |
| Year: | 2025 |
| Department: | School of Fashion and Textiles |
| Pages: | xix, 274 pages : color illustrations |
| Language: | English |
| Abstract: | Wearable flexible healthcare devices have the potential to provide real-time, continuous, and remote monitoring, and/or treatment, thereby alleviating the medical system burden, and reducing the need for patient hospital visits. Flexible, comfortable, and safe wearable healthcare devices, including both monitoring devices, and treatment devices, are preferred for their seamless, and accurate functionality. However, the performance of the current pressure sensation device is significantly influenced by the environment, such as temperature, and relative humidity, due to its material, and mechanism. This variability poses a challenge to maintain sensation fidelity. Furthermore, there is often a discrepancy between the sensor performance, and the specific requirement of the application, particularly in terms of the pressure sensation range, which varies across different needs. This increases the requirement for the sensor performance, like sensor linearity, sensitivity, and a wide dynamic range. To address these challenges, it is necessary to develop specific health monitoring devices to reduce the sensor performance requirement. It also can reduce the time for data processing, and energy consumption. On the other hand, there is a notable scarcity of wearable healthcare treatment devices. Current research predominantly focuses on wearable drug delivery, rather than energy-treatment. Adopting energy-treatment devices in wearable format would be highly valuable, as it can significantly enhance patient care. To address the above problems, a novel mechanoreceptor was designed, wherein the pressure threshold can be controlled through adopting the structure parameters, and materials. The interrelationship between the pressure threshold, and structural parameters was comprehensively studied. By increasing the material filling rate of the insulation cavity, the pressure threshold can be controlled in the range of 3 kPa to 297 kPa. In addition, by increasing the height of the PDMS, the pressure threshold can be controlled in the range of 54.84 kPa to 1466.78 kPa. Moreover, the pressure thresholds can also be modulated by altering the material modulus, compression area, and the size of the mechanoreceptor. Given the diversity of controllable dimensions, the processing requirements associated with any particular dimension can be reduced by leveraging synergies across multiple dimensions. This broadens the application potential. In addition, the introduction of PDMS structure into the insulation layer of the mechanoreceptors allows for an excellent on-off ratio, exceeding eight orders to magnitudes, comparable to commercial HMI interface. Otherwise, this mechanoreceptor also shows good reliability under repeated compressions (>40000 compression cycles), and laundries (20 laundry cycles). It is capable of functioning under 1 kHz compressions. The response time, and recovery time of the mechanoreceptor was only around 43 ms. Overall, this mechanoreceptor exhibits good mechanical, electrical, and textile properties, making it a promising candidate for advanced wearable healthcare devices. Additionally, a corresponding spiral mechanoreceptor array was designed, and fabricated, containing a total of 16 mechanoreceptors in series connection with flexible resistors. This array was developed to enhance data processing, and wearable connection, and features only two output electrodes for data processing, and power. It can be used for position identification based on different resistance output values. The resistance value of the mechanoreceptor was in the range of 1Ω to 50 kΩ, in which the resistance difference between mechanoreceptors was approximately 3.226 kΩ. This array’s on-off resistance value remains stable across different environments, including high temperature (50 °C), low temperature (-40°C ), cyclic temperature, underwater conditions (1 m depth), and under maximum mechanical load (100 N). Furthermore, this array also can function effectively under bending with good comfort. Finally, this novel mechanoreceptor, and the corresponding mechanoreceptor array were integrated into different wearable products to explore its potential in wearable applications with different pressure sensation requirements, like plantar pressure sensation (~250 kPa), and gait analysis (~30 kPa). Moreover, a pressure sensation platform was developed to detect both pressure, and position, potentially simulating the human skin’s pressure sensation mechanism. This advancement may pave the way for more sophisticated pressure sensation technology with stable performance across different environments. For the wearable energy treatment device, a comprehensive photobiomodulation evaluation system was established to assess the performance of the PBM devices from different aspects, including peak wavelength, wavelength shifting at different currents, systematic electrical properties, LED IV curve, irradiance, system irradiance distribution, and temperature variation throughout treatment. Two different types of commercial photobiomodulation devices were studied with the system to understand their functionality, and performance. Moreover, this help to establish the relationship between the effective photobiomodulation parameters, and the device settings/ design. This also provides a valuable insight into the challenge associated with developing wearable photobiomodulation devices, and even other energy-based treatment devices. A flexible photobiomodulation panel was developed with an appropriate LED light source to treat the radioactive dermatitis of the breast cancer patient. A group of LEDs was evaluated from different aspects, including wavelength, irradiance, voltage, and current to ensure optimal selection for photobiomodulation. Moreover, the design of the LED array was studied through simulation, and experiments to achieve the best configuration. The panel adopted a fabric-making pattern to realize good conformability onto the human body contour. Besides this, a study was conducted on the light efficiency of the wearable treatment device. This flexible photobiomodulation panel can be seamlessly integrated into the underwear for comfort, and convenience. This work illustrates a feasible pathway to transform energy-based treatment devices into wearable formats. Overall, this work comprehensively studied wearable healthcare devices, including pressure sensation techniques, and photobiomodulation devices. It deeply investigates the current challenges, and limitations of these devices, and explores potential solutions to address these issues. |
| Rights: | All rights reserved |
| Access: | open access |
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