PillStim

The design, development, and characterisation of a single-channel electrical stimulator for use in a single-use ingestible pill.

The University of Melbourne
Sam John, David Graydan
P-001
11 March 2026
Constraints
Mechanical 26 mm (L) × 11 mm (D) — PillCam dimensions
Electrode surface area 190 mm² — dome electrodes on ends of pill
Battery capacity 445 mWh/cm³ — silver oxide
Battery life 5 days
Stimulation type Biphasic
Stimulation frequency 1 – 10 Hz
Stimulation amplitude 10 – 5000 µA
Stimulation pulse width 100 – 500 ms
Stimulation compliance 14 V
Charge max per phase 500 µC
Charge balance < 100 nC net charge
Stimulation protocol To be advised
Considerations

Tissue Safety

Safe limit is 57 µC/phase (190 mm², 30 µC/cm²). Post-stimulation shorting handles residual charge; a DC blocking cap is optional but costs compliance headroom. A centre ring electrode enables per-hemisphere impedance checks — this may be essential since partial tissue contact reduces safe thresholds significantly.

Efficiency

Tissue stimulation should dominate power consumption. Since current is fixed, power drawn is 14 V × Istim, but power delivered to tissue is only Vt × Istim. Dynamically setting compliance voltage based on measured electrode impedance before each pulse minimises this overhead.

Device Safety

Redundant safety mechanisms — DC blocking capacitor and hardware charge limiting — prevent adverse effects in the event of malfunction.

Proposed Architectures
Concept A: Floating cap supply — Dickson charge pump with switched capacitors, uController, H-bridge, ADC feedback, DC blocking cap, and electrode/tissue interface
Concept B: Continuous inductive boost converter, uController, H-bridge, ADC feedback, DC blocking cap, and electrode/tissue interface
Deliverables
  1. 01
    Low-Resolution Simulation
    Ideal simulations confirming the fundamentals of the proposed architectures and ideal component values. Includes power consumption, efficiency, charge balance, and verification of stimulation compliance.
  2. 02
    Component Selection
    Based on simulation results and requirements, components and values will be selected and prepared for detailed simulation.
  3. 03
    High-Resolution Simulation
    Exact component models integrated and circuits characterised to verify all requirements are met.
  4. 04
    Layout
    Designs transferred to contractor for PCB layout and fabrication.
  5. 05
    Firmware
    Firmware written and tested using a development board. Additional test code written to validate hardware functionality.
  6. 06
    Bench Testing
    Fabricated boards fully characterised and validated against requirements.
  7. 07
    Report
    Preliminary report created for client review.
Terms
$50,000
Fixed fee — 50% up front, 50% on completion.
Covers all expenses associated with delivery of the project.
Info
Primary contact Kyle Slater
k@musicdust.com
+61 415 141 297
Company details Music Dust Pty Ltd
ABN 33 659 694 818
BSB 083-004 · ACC 511469302
Agreement
Prepared by
Kyle Slater signature
Kyle Slater
Director, Music Dust Pty Ltd
11 March 2026
Accepted by
 
The University of Melbourne
 
Music Dust