A 3D-Printed Capacitive Smart Insole for Plantar Pressure Monitoring

Abstract

Gait analysis refers to the systematic study of human locomotion and finds numerous applications in the fields of clinical monitoring, rehabilitation, sports science and robotics. Wearable sensors for real-time gait monitoring have emerged as an attractive alternative to the traditional clinical-based techniques, owing to their low cost and portability. In addition, 3D printing technology has recently drawn increased interest for the manufacturing of sensors, considering the advantages of diminished fabrication cost and time. In this study, we report the development of a 3D-printed capacitive smart insole for the measurement of plantar pressure. Initially, a novel 3D-printed capacitive pressure sensor was fabricated and its sensing performance was evaluated. The sensor exhibited a sensitivity of 1.19 MPa−1, a wide working pressure range (<872.4 kPa), excellent stability and durability (at least 2.280 cycles), great linearity (R2=0.993), fast response/recovery time (142–160 ms), low hysteresis (DH<10%) and the ability to support a broad spectrum of gait speeds (30–70 steps/min). Subsequently, 16 pressure sensors were integrated into a 3D-printed smart insole that was successfully applied for dynamic plantar pressure mapping and proven able to distinguish the various gait phases. We consider that the smart insole presented here is a simple, easy to manufacture and cost-effective solution with the potential for real-world applications.

Embedded Pressure Sensing Metamaterials using TPU-Graphene Composites and Additive Manufacturing

“…This is supported by previous studies, which have found that lattice structures display a power law relationship dependent on the structure relative density and compressive properties [47]- [49]. The three designs exhibited hysteresis during the loading and unloading cycle, a behaviour observed in TPU auxetic lattice structures fabricated using SLS [50] and in fused filament fabricated manufactured capacitive pressure sensors for plantar monitoring [51]. The compressive velocity of 4 and 30 mm • min −1 produced similar mean trajectories (Fig.…”

Gait Pattern Analysis: Integration of a Highly Sensitive Flexible Pressure Sensor on a Wireless Instrumented Insole

“…Precise, reliable, and meaningful gait measurements in both high and low-pressure regions, essential for detecting human movement, require soft and flexible sensors with high sensitivity and linearity [13,14]. These characteristics ensure the sensor's efficacy in accurately capturing the nuances of human motion, offering valuable insights applicable to both clinical and research settings.…”

“…Dynamic forces were also applied, as depicted in Figure 4B, revealing an increase in capacitance with increasing pressure. To verify the stability of capacitance under consistent force, a pressure of 100 kPa was applied to the sensor using a force gauge, and the capacitance was repeatedly measured, as shown in Figure 4C [11][12][13]. Figure 4D shows the variation in relative capacitive change for loading and unloading, which indicates low hysteresis.…”

“…Utilizing CPS as wearable sensors offers numerous advantages, such as extending sensor lifespan and reducing production costs by introducing cost-effective rapid manufacturing processes [12][13][14][15][16][17][18][19]. Additionally, CPS exhibits superior sensitivity and lower linear error rates compared to FSR.…”

“…Although this work achieved promising outcomes, it did not characterize walking patterns, preventing the comprehensive monitoring of the gait signal. In a previously reported sensor system from Samarentsis et al, a 3D-printed CPS-based smart insole was used, and displayed rapid response and relaxation times, as well as adaptability to various gait speeds [13]. In their study, the authors integrated sixteen pressure sensors hooked on a 3D-printed design to create a smart insole that effectively mapped the dynamic plantar pressure and could differentiate between different gait phases.…”