An experimental investigation on shape memory alloy dynamic splint for a finger joint application

To strengthen fingers which are injured in an accident, a new type of SMA (shape memory alloy)-made dynamic splint used for finger joints is proposed.The issue, here, is to clearly present the mechanism and control system of the dynamic splint. Four wires of the shape memory alloy (SMA – Ti50Ni45Cu5 with 1.0 mm in Φ) are arranged in parallel within silica-gel tubes. The finger glove made of six pieces of silica-gel tubing, which abare parallel to the fingers, is a flexible joint that moves during rehabilitation when the SMA is heated. Two kinds of dynamic splints (one, a fixed-type dynamic splint; and the other, a portable-type dynamic splint) are developed. The former, which has an adjustable mechanism to fit various fingers using a PC-based control system, is suitable in a medical clinic milieu. The latter, controlled by a microcontroller (PIC18F452), is suitable for home rehabilitation. Both splints incorporate the SMA's temperature-feedback system that keeps them within the appropriate safety range. The output force of the SMA-made dynamic splint develops in this study is 22 N that is sufficiently used in the rehabilitation.