| Author: | Ning, Sen |
| Title: | Design of textile-fabricated diabetic insole for enhancing foot thermal comfort |
| Advisors: | Yick, Kit-lun (SFT) Yip, Joanne (SFT) |
| Degree: | M.Phil. |
| Year: | 2024 |
| Subject: | Orthopedic shoes Foot -- Diseases -- Treatment Diabetes -- Complications -- Prevention Hong Kong Polytechnic University -- Dissertations |
| Department: | School of Fashion and Textiles |
| Pages: | xvi, 151 pages : color illustrations |
| Language: | English |
| Abstract: | Diabetes is a global public health issue in the 21st century that cause accelerated atherosclerosis and leads to an increase in elastic shear stiffness and a reduction in wound healing ability and sensitivity of the foot. This arises the risk of diabetic patients developing diabetic foot ulcers (DFUs). The use of diabetic footwear and orthosis is the most essential approach to preventing foot ulceration. However, due to the limitation of material choice, the diabetic insoles are mostly made of traditional foam with satisfactory pressure off-loading but poor permeability. Skin temperature and humidity have already been recognized as two risk factors for DFUs, the absence of a proper management approach means that the in-shoe high temperature and excessive moisture might cause deformation of the plantar foot tissues. Some novel approach of fabricate new materials for cushioning application have been investigated such as three-dimensional (3D) knitting and 3D printing technologies. Even so, their performance as an insole material during daily activities and locomotion is still unclear. The ultimate goal of this research is to develop a diabetic insole orthosis with the use of both a novel knitted textile and 3D printed materials to optimize the wear comfort in terms of the in- shoe environment and even distribution of plantar pressure with reference to experimental analysis. To understand the footwear and insole needs and preferences of the diabetic patient, a foot care program is conducted with a questionnaire for each participant. A total of 30 diabetic elderly between the ages of 55 to 75 years old comprised of 16 women and 14 men (mean: 64.9; standard deviation (SD): 6.27) were invited to answer the questionnaire about the problem or foot pain they are suffering using their current footwear in daily activities. A total of 30 diabetic patients are recruited. Their problem or foot pain using current footwear, as well as their footwear and insole preference were collected. Also, their practical use of footwear in daily activities was investigated. The foot pain of the diabetic patient was found mainly at the heel, forefoot, and medial side of the foot. Textile materials are found as the most common 1st layer of the insole currently used by the participants. The cushioning pad at the high-pressure region and arch pad is their preferred features on the insole. The findings provide useful references in the design of diabetic insoles. To investigate the thermal performance of different insole materials including traditional foam materials, novel textiles materials, and 3D printed materials, a wear trial has been conducted regarding the effect of the insole materials on the change of foot skin temperature and humidity during fast walking. Traditional insole materials which trap heat and moisture inside footwear cause discomfort to the wearer. Here, a novel textile-fabricated insole material with a 3D structure that offers good porosity and breathability for improving the footwear microclimate is proposed. Changes in foot skin temperature and humidity when wearing the textile-fabricated insole throughout treadmill walking are collected from 21 female subjects (age: 25.5 ± 4.5) and compared with traditional and 3D printed insoles. A subjective assessment of their perceived thermal comfort with various insole conditions is also conducted. In comparison to polyurethane, 3D printed thermoplastic polyurethane, and leather insoles, textile-fabricated insoles show no significant changes in foot skin temperature. Nevertheless, a significant reduction of the relative humidity of the skin of the sole (3.21%) and heel (24.41%) is found. The findings are a valuable reference for the fabrication of insoles with higher wear comfort. To design and develop an insole prototype that can effectively improve the thermal comfort of the insole with desirable plantar pressure distribution to reduce the rate of foot ulcers, a novel weft-knitted spacer fabric with foam inlays and a 3D printed insole with arch pad and auxetic heel pad was developed. Weft-knitted spacer fabric was fabricated with six knitting conditions with a combination of different inlay densities and spacer course densities. The effect of inlay density and spacer course densities on the performance of weft-knitted spacer fabrics regarding their thermal conductivity, evaporative resistance, compression behaviour, and impact force reduction was investigated. It was found that fabric with higher inlay density and /or spacer density tends to perform better in force reduction and compressive resistance. With the same inlay density, higher spacer density reduces air permeability. Also, the high density of inlay materials tends to increase evaporate resistance. A fabric shows the best overall performance with thermal conductivity of 0.071W/mK, a maximum compressive stress of 323.43 kPa, and force reduction of 70.07%, and air permeability of 35.96 ml/s/cm2, has been applied as the upper layer of the novel insole prototype. As for the 3D printed materials for insole application, a total of eight 3D prints with different structures using four different soft materials are demonstrated and evaluated by material test and wear trial. It was observed that the 3D printed materials in the auxetic structure show an excellent force reduction, a rapid reduction of compression force when removing the force from the materials, and outstanding water vapor permeability. The 3D printed re-entrance auxetic structural resin (80A hardness) exhibits an average of 12.7% pressure reduction at the rearfoot as a heel pad. A half-insole consisting of a heel pad in auxetic re-entrance structure, and an 3D arch pad was designed and printed by using resin to provide the required conforming foot shape, fit, support, as well as cushioning effect on the heel. The proposed orthotic insole is therefore comprised of the 3D half-insole and the novel spacer inlaid weft-knitted fabric. In laboratory wear trial, a total of 8 female participants were invited. Its offloading performance was measured. Compared to the commercial diabetic insoles, the insole developed in this research shows lower mean peak pressure (MPP) at the toes and rearfoot which is also able to maintain the most evenly distributed plantar pressure with all the regions <202 kPa. It also has the highest perceived comfort in all the foot regions. The offloading performance of the proposed insole prototype was verified by means of wear trial that a total of 23 diabetic elderly participants was invited. A reduction of plantar mean peak pressure up to 30.7% has been observed, while the plantar peak pressure was lower than 201 kPa in all foot regions. Aligned with the results from young participants, higher perceived comfort was reported when the textile insoles are worn in comparison to the market-available diabetic insoles. The weft-knitted spacer fabric with inlay and the 3D printed auxetic material structure proposed in this study provide an alternative material choice to advance the design and development of footwear insoles that improve wear comfort. The insole prototype fabricated by using 3D knitting and 3D printing technologies not only effectively improve in-shoe humidity and perceived comfort, but also offer desirable cushioning and offloading performance. The output of the study could extend to the development of customized insole orthosis to prevent the development of diabetic foot ulcers. |
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| Access: | open access |
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