Design and development of a low-cost biphasic charge-balanced functional electric stimulator and its clinical validation

Chandrashekhar Shendkar; Prasanna K. Lenka; Abhishek Biswas; Ratnesh Kumar; Manjunatha Mahadevappa

Design and development of a low-cost biphasic charge-balanced functional electric stimulator and its clinical validation

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Author(s): Chandrashekhar Shendkar ¹ ; Prasanna K. Lenka ² ; Abhishek Biswas ² ; Ratnesh Kumar ³ ; Manjunatha Mahadevappa ¹
- Affiliations: 1: School of Medical Science and Technology, Indian Institute of Technology (IIT), Kharagpur 721 302, West Bengal, India ;
  2: National Institute for the Orthopaedically Handicapped (NIOH)–Kolkata, Kolkata 700 090, West Bengal, India ;
  3: Department of Disability Affairs, Ministry of Social Justice and Empowerment, New Delhi 110001, India
Source: Volume 2, Issue 5, October 2015, p. 129 – 134
DOI: 10.1049/htl.2015.0001 , Online ISSN 2053-3713

Received 14/02/2015, Accepted 23/07/2015, Revised 20/07/2015, Published

Functional electric stimulators that produce near-ideal, charge-balanced biphasic stimulation waveforms with interphase delay are considered safer and more efficacious than conventional stimulators. An indigenously designed, low-cost, portable FES device named InStim is developed. It features a charge-balanced biphasic single channel. The authors present the complete design, mathematical analysis of the circuit and the clinical evaluation of the device. The developed circuit was tested on stroke patients affected by foot drop problems. It was tested both under laboratory conditions and in clinical settings. The key building blocks of this circuit are low dropout regulators, a DC–DC voltage booster and a single high-power current source OP-Amp with current-limiting capabilities. This allows the device to deliver high-voltage, constant current, biphasic pulses without the use of a bulky step-up transformer. The advantages of the proposed design over the currently existing devices include improved safety features (zero DC current, current-limiting mechanism and safe pulses), waveform morphology that causes less muscle fatigue, cost-effectiveness and compact power-efficient circuit design with minimal components. The device is also capable of producing appropriate ankle dorsiflexion in patients having foot drop problems of various Medical Research Council scale grades.

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Design and development of a low-cost biphasic charge-balanced functional electric stimulator and its clinical validation

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