Performance Assessment of Thermal Sensors for Hand Prostheses

Amputees using prostheses have a loss of somatosensory functions that should be restored to ensure a more stable grasp, slippage prevention, and protection from unbearable stimuli. Several studies show the necessity of integrating temperature sensors in prostheses to restore thermal sensations. The performance of the used sensors is usually not accurately analyzed when integrated into a prosthesis and a systematic testing protocol is generally missed. This study aims to compare systematically and rigorously the performance of commercial temperature sensors when integrated into a prosthetic fingertip. Four thermal sensors were selected. An experimental setup and a systematic testing protocol for sensor assessment were devised. The sensors were inserted into a 3-D printed fingertip and different object temperatures were considered. Moreover, a silicone layer was added to simulate the presence of a cosmetic glove and various object-to-sensor inclination angles were tested to reproduce a realistic contact. The optimal sensor for integration into a prosthetic fingertip was identified through a statistical analysis of the obtained results. The infrared (IR) sensor was selected, as it exhibited an average rise time
$\lt {0}.{01}~$
s and of
${0}.{04}~\pm ~{0}.{2}~$
s, with and without silicone, respectively, and a mean error (ME) of
${3}.{3}~^{\circ }\text {C}~\pm ~{5}.{1}~^{\circ } $
C and
${4}~^{\circ }\text {C}~\pm ~{5}.{4}~^{\circ } $
C with and without silicone, respectively. All the tested sensors encountered a degradation of performance when the fingertip was covered with silicone and positioned at the highest inclination. These observations emphasize the significance of utilizing the presented standardized method, to evaluate the performance of thermal sensors in a realistic environment.