Neurostimulation is the application of short electrical pulses to the surface of the skin for the purpose of stimulating the underlying nerves and muscles. In recent decades, neurostimulation has been used as part of a treatment called Functional Electrical Stimulation (FES) therapy to help restore mobility in the paralyzed limb muscles of stroke victims and those who have suffered spinal cord injuries. While carrying out research in areas such as pain reduction and sensory feedback, scientists have also used neurostimulation to study the effect of electrical current on neurons.

Historically, the delivery of neurostimulation has required the purchase of expensive, research-grade equipment or the expensive, time-consuming construction of custom hardware. NeuroStimDuino provides an open-source alternative in the form of an Arduino shield.

Affordable, Accessible, and Easy to Use

NeuroStimDuino was designed to help anyone with an interest in neuroscience—students, researchers, and hobbyists alike—to study the effects of neurostimulation on muscle contraction. It comes with an I²C interface through which external microcontroller boards like the Arduino Due can be used to generate different stimulation patterns and control other aspects of its operation. Each NeuroStimDuino shield has two independent output channels, which can be used to alternate the contraction of flexor and extensor muscles or to contract various muscles simultaneously. By stacking multiple shields, additional output channels can be made available.

Note: A single output channel on NeuroStimDuino is capped at 25 mA, which is sufficient to contract small muscles but insufficient to contract large ones. Large muscles can be contracted by combining the two output channels of NeuroStimDuinos in parallel.

Opens the Door to Many Different Areas of Research

NeuroStimDuino is a platform technology with many possible applications. It can be used to conduct research on how neurostimulation affects pain management and the restoration of mobility to paralyzed extremities. It can also provide sensory feedback to amputees and stimulate the transcutaneous vagus nerve to study the effects of neurostimulation on depression, arthritis, and other conditions.

WARNING: This instrument is intended for RESEARCH PURPOSES ONLY. It is not intended for human or animal use. Neuralaxy LLC does not assume responsibility for injury or damage due to the misuse of this instrument.

Features

• Generates biphasic, rectangular, and constant current stimulation pulses with programmable frequency, pulse-width, and amplitude
• Stimulation pulses are charge-balanced, consisting of a cathodic phase followed by an anodic phase of equal or unequal amplitudes (i.e. the waveform shape can be symmetrical or asymmetrical).
• Can be configured, over I²C, from an external microcontroller acting as the controller
• Can be used as an Arduino shield due to pin-compatibility with Arduino Due and MEGA boards
• Has two independent output channels per board. Multiple boards can be stacked to generate up to 256 channels.
• Onboard opto-isolators separate digital and analog signals
• Can be powered by a 9 V battery connected to a DC input or by an external 5 V input on VIN. For proper operation, we recommend two Li-Ion batteries (e.g. 18650s) connected in series. (Batteries not included.)
• Onboard LEDs visually indicate when neurostimulation is delivered, and a precision current-sense amplifier provides a voltage output proportional to the stimulation current.
• Includes several safety features such as fuses, an emergency OFF switch, and solid-state relays to shunt inputs with low impedance resistors
• Comes with a pair of 2 mm pin-style lead wires to connect with standard, reusable, hydrogel-based stimulation electrodes
• The optional Accessory Kit includes four 1.25-inch round and four 2-inch square hydrogel electrodes, a pair of lead wires, and a pair of bifurcation cables.

Technical Specifications

• Adjustable current output range: +/- 25 mA, resolution 250 µA/step
• Adjustable stimulation frequency range: 1 – 100 Hz, pulse-width 0 – 2 ms
• Maximum compliance voltage: +/- 72 V
• The onboard 16-bit dsPIC33F Microcontroller (40 MIPS, 256 KB flash memory) operates as an I²C peripheral with a programmable, 7-bit address.
• Stimulation current output can be measured using the onboard 12-bit ADC or an external ADC.
• The PCB includes a microUSB interface but the components are not populated. (Upon request, we are happy to provide a list of the necessary components.) If populated, this interface can be used to control NeuroStimDuino from a PC by way of serial commands.

Comparisons

Board Layout

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Pinout Diagram

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Support & Documentation

For instructions and video tutorials on the placement of stimulation electrodes to evoke various muscle contractions, please refer to Electrode Placement & Functional Movement, courtesy of Dr. Lucinda Baker, Associate Professor (retired) at the University of Southern California and Axelgaard Manufacturing Co., Ltd. For NeuroStimDuino software and design files, please see our GitHub repository. If you have questions, you can reach us using the Ask a technical quesiton link on our campaign page.

Manufacturing Plan

NeuroStimDuino PCBs will be manufactured, assembled, programmed, and tested in India. We have also negotiated pricing for larger batches in case there is sufficient interest to justify runs of 50 or more boards. We will purchase accessories (cables, electrodes, and battery holders) from an online vendor and package them alongside the NeuroStimDuino boards.

Fulfillment & Logistics

We will provide NeuroStimDuino boards and accessories to Crowd Supply, whose fulfillment partner, Mouser Electronics, will handle the final shipment to backers, including export compliance and customs logistics for international orders.

Risks & Challenges

We have mitigated manufacturing risk by only using components that can be easily sourced from Mouser or Digikey. Furthermore, as you can see in our campaign video, we have already produced a small lot of (ten) production units so we could test their performance. While we have decided to manufacture the boards in India, we have also run the BOM through vendors in China in case there are any COVID-19 related holdups in India. As things stand, pandemic-related lockdowns have been lifted, and Indian assembly houses are operating normally.