Fuel Cell Cloth Holders — From Algorithmic Design to Prototype using PicoGK

This project illustrates how computational geometry and additive manufacturing enable rapid development of functional components for bioelectrochemical fuel cells. Our objective was to design a holder that securely positions carbon cloth for both anode and cathode while maximising active surface area. The result integrates state-of-the-art surface chemistry with precise geometric design.

1. Design Requirements

Hold carbon cloth securely for both anode and cathode.
Maximise available carbon cloth surface area for electrochemical reactions.
Ensure manufacturability using additive manufacturing processes.
Maintain mechanical stability under operation.

2. Concept Development

The creative foundation for this design was developed by Masoumeh Tahimehr at Pipeline Organics. Her initial sketch introduced a dual-spiral structure concept that inspired the algorithmic generation of both the anode and cathode holders.

3. Computational Engineering Algorithm

The geometry was generated using parametric algorithms written in C# by Eric Lehder. The logic proceeds in three main stages:

Create spiral stages parametrically with adjustable radius and pitch.
Connect the spirals using spiral-patterned struts for structural integrity.
Generate the cathode holder through a circular pattern of holders.

This spiral-based algorithm allows precise control of spacing and volume fraction, ensuring mechanical efficiency and maximum electrode exposure.

// Generate spiral-based lattice
for (int j = 0; j < fZMax_n; j++)
{
    // Z position for this spiral stage
    float fZ = fElecZStrt + (fElecH - fElecZStrt) * (j / (fZMax_n - 1));

    // Create spiral layer
    for (int i = 0; i < nRadPtsTot; i++)
    {
        float fRadius = fRadStrt + (fRadMax - fRadStrt) * (i / nRadPtsTot);
        float fPhi = ((2 * MathF.PI * nTurns) / nRadPtsTot) * i;

        Vector3 vecSpPt = VecOperations.vecGetCylPoint(fRadius, fPhi, fZ);
        latSpiral.AddSphere(vecSpPt, fSprWallth);
    }

    // Add spiral-patterned connection struts
    if (j < fZMax_n - 1)
    {
        for (int i = 0; i < nRadPtsTotVerts; i++)
        {
            float fRadius2 = fRadStrt + (fRadMax - fRadStrt) * (i / nRadPtsTotVerts);
            float fRadTurns = 2 * MathF.PI * nTurns;
            float fPhi2 = (fRadTurns / nRadPtsTotVerts) * i;
            float fZ2 = fElecZStrt + (fElecH - fElecZStrt) * ((j + 1) / (fZMax_n - 1));

            Vector3 vecSpPt2 = VecOperations.vecGetCylPoint(fRadius2, fPhi2, fZ);
            Vector3 vecSpPt3 = VecOperations.vecGetCylPoint(fRadius2, fPhi2, fZ2);

            latSpiral.AddBeam(vecSpPt2, fSprWallth, vecSpPt3, fSprWallth);
        }
    }

    // Connect the ends of the spiral
    Vector3 vecSpPtEnd = VecOperations.vecGetCylPoint(fRadius, fPhi, fZ2);
    latSpiral.AddBeam(vecSpPt, fSprWallth, vecSpPtEnd, fSprWallth);
}

// Convert to voxel representation
Voxels voxSpir = new(latSpiral);

// Generate spiral-based lattice
for (int j = 0; j < fZMax_n; j++)
{
    // Z position for this spiral stage
    float fZ = fElecZStrt + (fElecH - fElecZStrt) * (j / (fZMax_n - 1));

    // Create spiral layer
    for (int i = 0; i < nRadPtsTot; i++)
    {
        float fRadius = fRadStrt + (fRadMax - fRadStrt) * (i / nRadPtsTot);
        float fPhi = ((2 * MathF.PI * nTurns) / nRadPtsTot) * i;

        Vector3 vecSpPt = VecOperations.vecGetCylPoint(fRadius, fPhi, fZ);
        latSpiral.AddSphere(vecSpPt, fSprWallth);
    }

    // Add spiral-patterned connection struts
    if (j < fZMax_n - 1)
    {
        for (int i = 0; i < nRadPtsTotVerts; i++)
        {
            float fRadius2 = fRadStrt + (fRadMax - fRadStrt) * (i / nRadPtsTotVerts);
            float fRadTurns = 2 * MathF.PI * nTurns;
            float fPhi2 = (fRadTurns / nRadPtsTotVerts) * i;
            float fZ2 = fElecZStrt + (fElecH - fElecZStrt) * ((j + 1) / (fZMax_n - 1));

            Vector3 vecSpPt2 = VecOperations.vecGetCylPoint(fRadius2, fPhi2, fZ);
            Vector3 vecSpPt3 = VecOperations.vecGetCylPoint(fRadius2, fPhi2, fZ2);

            latSpiral.AddBeam(vecSpPt2, fSprWallth, vecSpPt3, fSprWallth);
        }
    }

    // Connect the ends of the spiral
    Vector3 vecSpPtEnd = VecOperations.vecGetCylPoint(fRadius, fPhi, fZ2);
    latSpiral.AddBeam(vecSpPt, fSprWallth, vecSpPtEnd, fSprWallth);
}

// Convert to voxel representation
Voxels voxSpir = new(latSpiral);

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4. Prototyping and Printing

The final 3D model was exported to STL and printed by Apoorva Parmar at Pipeline Organics. The prototype demonstrates excellent rigidity and precision, enabling smooth insertion of carbon cloth for both electrodes.

5. Next Steps

Future iterations will integrate catalytic coatings and advanced surface chemistry developed in-house to enhance charge transfer and biocompatibility. Additional work will focus on optimising flow dynamics around the electrode surface and improving print efficiency.

6. Summary

This work showcases how computational geometry and additive manufacturing can rapidly transform conceptual sketches into test-ready components. The integration of advanced surface chemistry marks an important step toward scalable, high-efficiency bioelectrochemical energy systems.