Non-clinical testing
A battery of electrical and mechanical bench tests was conducted with the NuroSleeve to ensure that its specifications met the device requirements. The requirements evaluated included hand splint ROM, grasp force and speed, battery life, and the total life cycle of the splint. Our goal was to allow people to grasp objects weighing up to 1.22 kg. To accomplish this, based on the calculation presented below, our system, which has a static coefficient of friction of 0.90, requires 13,3 N of force.In which m is the weight of the intended object to grasp, g is the gravitational acceleration, µ is the static coefficient of friction, and F is the required force. Our system is capable of producing a force of 22.4 N, but we do not wish to operate at the limit, so we conducted the experiments based on our recommendation for usage, which is 13.3 N. While manual measurements were carried out for most requirements, accelerated life testing was also implemented using two specific setups, as shown in Fig. Test Bench for the NuroSleeve with added resistance with springsThe second accelerated life test deployed a similar setup with the addition of three springs connected to the splint finger piece: one for opposing hand opening and two for opposing hand closing or grasping. The springs induced a variable load with a maximum of 13.3 N in both directions. The formula for calculating the force induced by the springs is provided below:F is the force opposing hand opening; K1 is the spring constant of the single spring opposing hand opening; K2 and K3 are the spring constants of the double springs opposing hand closing; L is the maximum possible spring enlongation; and To determine the battery life of the NuroSleeve, its power consumption was analyzed. In standby or FES mode, the NuroSleeve PCB with all sensors connected consumes 175 mA of continuous current; movement of the linear actuator increases the current consumption to between 275 and 375 mA, depending on the torque generated. Assuming a nearly linear relationship between battery capacity and operating time due to the extremely low discharge current rate [