Department of Innovation Engineering, University of Salento, 73100 Lecce, Italy.
Facultad de Ingeniería, Universidad Panamericana, Aguascalientes 20290, Mexico.
Sensors (Basel). 2021 Jul 1;21(13):4539. doi: 10.3390/s21134539.
The evolution of low power electronics and the availability of new smart materials are opening new frontiers to develop wearable systems for medical applications, lifestyle monitoring, and performance detection. This paper presents the development and realization of a novel smart insole for monitoring the plantar pressure distribution and gait parameters; indeed, it includes a piezoresistive sensing matrix based on a Velostat layer for transducing applied pressure into an electric signal. At first, an accurate and complete characterization of Velostat-based pressure sensors is reported as a function of sizes, support material, and pressure trend. The realization and testing of a low-cost and reliable piezoresistive sensing matrix based on a sandwich structure are discussed. This last is interfaced with a low power conditioning and processing section based on an Arduino Lilypad board and an analog multiplexer for acquiring the pressure data. The insole includes a 3-axis capacitive accelerometer for detecting the gait parameters (swing time and stance phase time) featuring the walking. A Bluetooth Low Energy (BLE) 5.0 module is included for transmitting in real-time the acquired data toward a PC, tablet or smartphone, for displaying and processing them using a custom Processing application. Moreover, the smart insole is equipped with a piezoelectric harvesting section for scavenging energy from walking. The onfield tests indicate that for a walking speed higher than 1 ms, the device's power requirements (i.e., P¯=5.84 mW) was fulfilled. However, more than 9 days of autonomy are guaranteed by the integrated 380-mAh Lipo battery in the total absence of energy contributions from the harvesting section.
低功耗电子技术的发展和新型智能材料的可用性正在为医疗应用、生活方式监测和性能检测开发可穿戴系统开辟新的前沿。本文介绍了一种新型智能鞋垫的开发和实现，用于监测足底压力分布和步态参数；实际上，它包括一个基于 Velostat 层的压阻传感矩阵，用于将施加的压力转换为电信号。首先，报告了基于 Velostat 的压力传感器的精确和完整特性，作为尺寸、支撑材料和压力趋势的函数。讨论了基于夹层结构的低成本、可靠的压阻传感矩阵的实现和测试。最后一部分与基于 Arduino Lilypad 板和模拟多路复用器的低功耗调理和处理部分接口，用于获取压力数据。鞋垫包括用于检测步态参数（摆动时间和站立阶段时间）的 3 轴电容加速度计，用于检测行走特征。包括一个蓝牙低能 (BLE) 5.0 模块，用于实时将采集到的数据传输到 PC、平板电脑或智能手机上，并使用自定义处理应用程序对其进行显示和处理。此外，智能鞋垫配备了一个压电能量收集部分，用于从行走中获取能量。现场测试表明，对于步行速度高于 1 ms 的情况，设备的功率需求（即 P¯=5.84 mW）得到了满足。然而，集成的 380 mAh Lipo 电池在没有能量收集部分贡献的情况下，保证了超过 9 天的自主运行时间。
