Hardware Design

A modular EEG cap,
designed and built from scratch.

Built during my PhD when off-the-shelf solutions weren't an option. I taught myself 3D design and printing to make it happen.

The goal: a single-channel EEG cap that could be reliably used in a real research setting — without specialist equipment or a technician to set it up.

Problems to solve

SecureMust stay fixed on any head, including long or thick hair
ConductiveGel must be applied and topped up without disturbing the setup
ComfortableFirm enough to hold, but not uncomfortably tight
ComparablePositioned to the 10-20 system so results sit within wider EEG research
Assembled EEG cap fitted on a mannequin head form

A finished cap fitted on a head form, showing strap routing, electrode placement, and the Pz measurement site.

Components
Electrode hold components
Core component

Electrode Hold

  • Secures the electrode — the two halves screw together, locking it in place
  • Holds gel — conductive gel is applied directly inside the hold
  • Accepts top-ups — a port allows more gel to be injected after the cap is fitted, via syringe
  • Clips in cleanly — slots through the nut and bolt; electrodes can be added or removed without disturbing the cap

When measuring a single channel, only that one site needs cleaning — no full hair wash required.

Electrode hold 3D render showing gel injection port

Detail — Gel injection port

Topping up without disturbing the cap

  • Top-up after fitting — the initial gel is rarely enough once the cap is secured
  • Syringe access — the port is sized for a syringe tip to inject gel directly to the site
  • Visible marker — a white ring is printed around the port, easy to spot in low light or under hair
Joint component 3D render
Adjustable

Joint

  • Clips the elastic bands together
  • Fastened or released on-site without tools
  • Allows the cap to be resized to fit any head
Nut and bolt components
Fastening

Nut & Bolt

  • Joins the elastic bands and anchors the electrode hold
  • Central hole sized precisely for the electrode hold rod
Precision fit Band anchor Tool-free removal
Assembly
Cap straps laid out flat

Step 1

Thread the straps

  • Elastic bands are threaded through the joint connectors and sized to fit
  • A hair tie secures the anchor point at the crown
  • Two bands fasten under the chin using hook-and-loop (velcro) closures

Step 2

Assemble the electrode hold

  • The electrode is placed inside the hold
  • The two halves are screwed together to secure it
Electrode hold assembly close-up
Electrode seated on cap on head form

Step 3

Seat the electrode and inject gel

  • The assembled hold is passed through the target nut and bolt — in this case, Pz
  • Gel is injected through the port
  • Impedance is checked before recording begins

Ready for the next participant in ten minutes.

After use, each component can be cleaned and reassembled quickly. With traditional EEG caps, that turnaround isn't possible.