For centuries, manufacturing has been about carving, sculpting, or molding a block of material. But what if we could build objects piece by tiny, programmable piece, controlling not just their shape, but their very essence?
Imagine a 3D-printed medical implant that is rigid on one end to anchor to bone, but soft and flexible on the other to interact with muscle. Envision a soft robot that can bend and twist with the dexterity of an elephant's trunk, not through complex mechanics, but because its very material is programmed to move. This is the future promised by voxel-based additive manufacturing, a revolutionary approach that provides unprecedented spatial control over material properties, turning passive objects into active, functional devices.
Think of your favorite digital photograph. If you zoom in close enough, you will see it is made of thousands of tiny, colored squares—pixels. Each pixel is a single point of color that, when combined with millions of others, forms a complete image.
A voxel is the three-dimensional equivalent of a pixel. The term is short for "volumetric pixel." It represents a tiny, discrete cube of volume in 3D space, the fundamental building block of a digital model 1 . But unlike a pixel that only holds color information, a voxel can be programmed with a wealth of data, including material composition, stiffness, density, and even thermal or electrical properties 1 .
3D equivalent of a pixel with programmable properties
Each voxel can have unique properties
To build an object with voxels is to assemble it from a digital LEGO set where every single brick can have its own unique instructions. This allows manufacturers to create complex geometries and intricate internal structures that are impossible with traditional methods, enabling innovations in fields from medical implants to aerospace components 1 .
The true power of voxels lies in their ability to construct what are known as digital materials. These are not new, homogenous substances invented in a chemistry lab. Instead, they are composite materials whose overall properties are determined by the microscopic arrangement of their constituent parts, much like a digital image uses a pattern of red, green, and blue pixels to create a spectrum of colors.
The following table details key components used in pioneering voxel research to create digitally controlled material properties.
| Component | Function | Example in Research |
|---|---|---|
| Vero (Rigid Polymer) | Serves as the stiff, structural inclusion within a voxel to increase overall strength and modulus 4 . | Mixture of isobornyl acrylate, acrylic monomer, urethane acrylate, and photoinitiator 4 . |
| Tango (Elastomeric Polymer) | Acts as the soft, flexible matrix, allowing for elasticity and large deformation 4 . | Polymerized urethane acrylate oligomer and methacrylate oligomer 4 . |
| Grayscale Value (G) | A digital instruction that controls UV light intensity during printing, determining the degree of curing and final material properties 5 . | Values from 0 (nearly zero light) to 1 (full light) create a gradient from soft to stiff in a single resin 5 . |
| Photoinitiator | A chemical that reacts upon exposure to specific light, initiating the polymerization process that solidifies the liquid resin 4 . | A key component in both Vero and Tango polymers 4 . |
While multi-material jetting uses different materials to create voxels, another powerful technique achieves similar results with a single resin. Grayscale Digital Light Processing (DLP) printing controls material properties by varying the light intensity used to cure the resin.
In a recent study, researchers developed a comprehensive framework for designing and fabricating soft robots using grayscale DLP 5 . The process is as follows:
Higher grayscale values produce stiffer materials
The grayscale DLP process enabled the creation of complex, functionally graded structures. To demonstrate this, the researchers printed two human hand models 5 :
Entirely soft structure that deforms uniformly under pressure.
Rigid "bones" with soft "tissue" that resists deformation in specific areas.
This experiment perfectly illustrates how voxel-level control can decouple an object's form from its function, creating complex, anisotropic behaviors within a single, seamlessly printed structure 5 .
Predicting how these voxel-designed structures will behave is complex. To address this, the team combined their printing process with a voxel-based finite-element (FE) model 5 . This computational tool treats each voxel as an individual unit with its own grayscale-dependent mechanical properties, allowing for fast and efficient simulation of how the entire structure will bend, twist, and deform.
The transition from pixel-based images to voxel-based manufacturing marks a paradigm shift. It moves us beyond creating static, uniform objects and into an era of spatially programmed matter. The implications are vast:
Robots can be designed with embodied intelligence, where the very material of their limbs is programmed for specific, complex motions, mimicking the elegant efficiency of an elephant's trunk 5 .
Implants and prosthetics can be graded to perfectly match the mechanical environment of the human body—hard like bone on one end and soft like cartilage on the other—improving integration and comfort 1 .
The principles of voxel-based design are being applied in architecture, using reusable "H-blocks" to create structures that can be disassembled and reconfigured, dramatically reducing material waste .
As with any emerging technology, challenges remain. Managing the immense computational data for complex voxel models and increasing printing speeds are active areas of research 1 7 . However, the trajectory is clear. By mastering the voxel, we are not just learning to build things better. We are learning to build better things, engineering them from the inside out and unlocking a new dimension of design freedom. The future of manufacturing is not just shaped; it is programmed.
References will be added here in the final version.