How Lattice Midsoles Turn Each Step Into Forward Motion

Foam midsoles have served footwear well for decades, but they make a blunt compromise: one material property applied uniformly, regardless of where the foot actually loads. The 3D-printed lattice midsole breaks that constraint by letting designers specify stiffness, cushioning, and rebound direction strut by strut. The adidas 4DFWD, made with Carbon's Digital Light Synthesis process, brought this from laboratory prototype to retail product and showed what the geometry can do.

Why foam hits a design ceiling

Conventional foam is isotropic, meaning it responds the same way in every direction. Compress it from the side and it behaves roughly as it does from above. That uniformity is useful for manufacturing but limiting for performance. A runner's foot does not load a midsole uniformly; heel strike, midstance, and toe-off each create different force vectors in different zones. Foam must be tuned as a compromise across all of them, or engineered in multiple bonded layers, each adding weight and process complexity. A printed lattice sidesteps this by treating each region of the midsole as an independent design variable.

The 4DFWD midsole and the bowtie cell

The adidas 4DFWD midsole, produced using Carbon's Digital Light Synthesis process, contains more than 10,000 individual struts arranged in a proprietary bowtie-shaped cell called the FWD CELL. The cell is deliberately anisotropic: under vertical load from the runner's weight, it deforms preferentially in the forward direction rather than spreading force outward or upward. This channelled deformation is not a passive material property; it is an engineered geometric response built into the cell shape itself.

Carbon's Digital Light Synthesis cures a liquid resin layer by layer with ultraviolet light through a transparent window, allowing the fine strut detail and complex cell geometries the design requires. The 4DFWD used a partially bio-based version of the resin, with Carbon reporting approximately 40 percent bio-based content by weight, which reduces the carbon footprint of the part without changing the geometric performance logic.

What density tuning actually does

Density tuning means varying the cell size or strut thickness across the midsole so that different zones have different stiffness and energy return characteristics. In the 4DFWD, the forefoot and heel regions have different lattice densities to balance cushioning against propulsive response. Denser zones, where struts are packed more tightly, resist deformation and provide support; sparser zones deform more freely, absorbing energy and releasing it directionally on rebound.

This is the same principle that makes functionally graded materials useful in aerospace and medical implants, applied to the everyday geometry of a running shoe. The difference is that a printed lattice achieves the gradient in a single manufacturing step, whereas a graded foam requires multiple pours or laminated layers that may delaminate over time.

Reported performance results

Carbon and adidas reported that the 4DFWD midsole delivered approximately three times the forward motion of the previous 4D midsole under lab testing conditions, alongside roughly 15 percent less braking force and approximately 23 percent more cushioning. These numbers come from the companies' own testing and should be read in that context, but the directional finding is consistent with what the geometry predicts: a cell shaped to deform forward will redirect more of the runner's downward force into horizontal propulsion, and more compliance in the cushioning zones will absorb peak impact force before it reaches the body.

Why geometry is the lever, not the material

The 4DFWD resin is not an extraordinary material. Its mechanical properties are unremarkable compared with engineering polymers used in load-bearing applications. What is extraordinary is the arrangement: thousands of struts oriented so that the structure behaves anisotropically at the macro scale. The resin simply carries the force; the geometry decides where that force goes. This is the hollow-tube principle operating in three dimensions, the same insight that makes a lattice stronger per unit weight than the same material in a solid block.

It also means improvements come primarily from redesigning the geometry, not from switching materials. A better cell shape, a tighter gradient, or a more precisely tuned anisotropy ratio will outperform a material upgrade applied to the same cell. For footwear companies, that shifts R&D effort toward computational geometry and simulation rather than polymer chemistry, a significant change in how midsole development works.

What this means for other products

The midsole is a template, not a one-off application. The design logic, tune density by zone, shape the cell for directional response, print the whole thing in a single step, applies equally to helmet liners, seat cushions, orthotic insoles, prosthetic sockets, and any product where cushioning and directional force response matter. Each application has its own load case, which means its own optimal cell geometry and gradient map, but the underlying approach is the same. The 4DFWD demonstrated that a printed lattice midsole can survive the manufacturing volumes and durability demands of a consumer product, removing the proof-of-concept risk for adjacent industries.

Key takeaways

• A 3D-printed lattice midsole replaces foam with thousands of tunable struts; density and cell shape vary by zone to match what each part of the foot needs.
• The adidas 4DFWD uses a bowtie FWD CELL made with Carbon's Digital Light Synthesis; its anisotropic geometry channels vertical load into forward propulsion.
• Performance improvements come from redesigning the geometry, not upgrading the material; the resin is ordinary, the arrangement is not.
• The midsole template, density grading plus directional cell geometry in a single printed step, applies to helmets, orthotics, seating, and any cushioning product.

Related reading

• How Graded-Density Lattices Put Stiffness Where You Need It
• Separating Compression and Tension Inside a Lattice
• How Lattices Absorb Energy in a Crash or Impact

Frequently asked questions

What is the adidas 4DFWD midsole made of?

The 4DFWD midsole is printed from a partially bio-based photopolymer resin using Carbon's Digital Light Synthesis process, a form of photopolymerization that cures liquid resin with ultraviolet light. The lattice geometry, not the resin chemistry, provides the performance advantage.

How many struts are in a printed lattice midsole?

The adidas 4DFWD contains more than 10,000 individual struts. The exact count varies with shoe size and zone density, but the point is that each strut is a design variable that can be tuned independently for stiffness, thickness, and orientation.

Is a 3D-printed lattice midsole more durable than foam?

Durability depends on the resin and cell geometry chosen. The 4DFWD reached commercial scale with standard footwear durability requirements, so printed lattices can match foam in service life. Unlike foam, a lattice does not compress permanently over time in the same way, though individual struts can fatigue under high cycle loads if not designed carefully.

Can the lattice cell geometry be changed for different sports?

Yes, and this is one of the main advantages. A running shoe, a basketball shoe, and a hiking boot all have different load profiles. The same printing process can produce midsoles with entirely different cell shapes and density gradients for each application, without retooling a physical mould.

Why does anisotropy matter in a midsole?

An anisotropic midsole responds differently depending on the direction of the applied force. A cell shaped to deform preferentially forward converts more of the runner's downward push into horizontal motion, which is what the 4DFWD's bowtie cell is designed to do. An isotropic foam spreads that energy in all directions, returning less of it as forward propulsion.