Hand splints actuators

This chapter presents preliminary investigations on the use of dielectric elastomer actuators as active eomponents of a specific type of orthotic systems, known as hand splints , used for finger or hand rehabilitation. 

This chapter describes an actuated dynamic hand splint with variable compliance regulated by new DE contractile actuators. The concept is described below, with reference to Figure 24.4. 

Figure 24.4 Dynamic hand splints (top) example of a passive dynamic splint equipped with an elastic band (bottom) schematic drawing of the proposed concept the passive elastic band is substituted with active elastic actuators.

To develop a wearable dynamic hand splint with electrically variable compliance, the concept described here relies on the use of linear contractile DE actuators. The idea is to use these actuators as active elastic substitutes of the linear passive elastic components of traditional splints, as sketched in Figiure 24.4. 

The technical design of the splint and the related dimensioning of the actuators have necessarily to take into account, as a fundamental specification, the maximum antagonist force that the actuators should be able to offer. An analysis of the state-of-the-art of hand splints for finger rehabilitations showed a chronic lack of extensive and comparable data on suitable rehabilitation forces adopted in the clinical practice. However, as a special case. 

Figure 24.7 Design of a hand splint equipped with linear dielectric elastomer actuators, their high voltage electronics and a load cell.

Figure 24.9 Prototype dynamic hand splint equipped with silicone folded actuators, high voltage electronics and load cell.

The combination of these results provides a demonstration of the MRI compatibility of the actuators considered. Accordingly, this outcome encourages the development of MRI-compatible, easily wearable and cheap hand splints equipped with such a type of polymer device. 

Figure 24.16 Schematic drawing of the concept of a myoelectrically controlled hand splint. EMC signals are recorded by means of surface electrodes and are processed by a myoelectric controller that drives the actuators of the splint.

Future developments should be aimed at developing actuators with improved performances, in order to enlarge die admissible working range of the hand splint. Moreover, an MRI-compatible version of the system and an EMG controlled one are envisaged as further parallel developments. 

Outside of biomimetics, dielectric elastomers may still be of use in other human-related applications including refreshable Braille devices [260, 282-284], hand rehabilitation splints [285], MRI compatible machines [247, 286-288], micro-fluidic devices [289, 290], force feedback [251], and wearable tactile interfaces [284, 291]. Oflier potential apphcations include actuators for hghter-than-air vehicles [292, 293], tunable phononic crystals [294—296], and variable phase retarders [297]. Beck et al. have also developed a sub-100 run resolution... 

Carpi F, Mannini A, De Rossi D (2007) Elastomeric contractile actuators for hand rehabilitation splints. Proc SPIE 6927 692705... 

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