Engineering Flexibility: Advances in Printing Malleable Objects

Achieving high flexibility and malleability in printed components opens up exciting possibilities in areas like soft robotics, customized medical devices, and next-generation consumer products. Engineers have made impressive advances in materials science and manufacturing processes that enable highly flexible and compliant 3D printing across applications.

But what are some of the key innovations bringing new levels of flexibility to additive manufacturing? Here we explore some of the most promising developments.

1. Flexible Materials Development

Ongoing materials research has produced novel polymers and composites with exceptional flexibility, elasticity, and durability when 3D printed. These include:

Thermoplastic Polyurethanes (TPUs)

Thanks to their segmented block copolymer structure, TPUs exhibit an exceptional combination of high elasticity, tear strength, and abrasion resistance. By carefully controlling the hard and soft segment mixing ratios, engineers can finely tune the shore hardness and flexibility to match application needs.

Shape Memory Polymers (SMPs)

SMPs demonstrate the unique ability to transform shape in response to temperature changes or other external stimuli. This makes them attractive for flexible printed components like self-deploying structures or biomedical devices. Material jetting now allows printing complex SMP geometries with precision.

Liquid Silicone Rubbers (LSRs)

LSRs offer very high tear strength and flexibility combined with biocompatibility, making them ideal for skin-contacting wearables and medical devices. New vat photopolymerization techniques print intricate LSR structures with exceptional flexibility.

Graphene-enhanced Composites

Strategic dispersion of graphene flakes into TPU filaments significantly improves tensile strength, elongation at break, and flexibility. Graphene-TPU composites enable fused deposition modeling of durable, flexible components.

2. Advanced Printing Processes

In addition to new materials, engineers have developed several innovative printing processes that impart exceptional flexibility into components:

Microlattice Structures

By using optimized lattice-based infills rather than solid structures, printed parts gain high compressibility and shock absorption while minimizing stiffness. The carefully designed microlattices collapse and rebound elastically under deformation.

In-Process Strain Alignment

Precisely applied strains through integrated heated rollers and conveyors during printing aligns polymer chains along load directions. This enhances inter-layer adhesion and component flexibility.

Short Fiber Reinforced Composites

Mixing discontinuous micron-scale fibers into extruded filament feedstocks approaches the performance of injection molded long fiber composites. Printed fiber reinforced components demonstrate superior strength combined with high flexibility.

3. Integrated Post-Processing

Secondary processing techniques performed on parts immediately after printing provide additional flexibility boosting mechanisms:

Polymer Infiltration

Infusing micro-porous printed composites with low viscosity resins enhances matrix connectivity. This improves mechanical stability and component flexibility compared to neat printed counterparts.

Ozone Exposure Treatment

Controlled ozone treatment increases the surface energy of printed parts, enabling better wetting and deeper penetration of infiltrating polymer resins. This further aids flexibility.

Strategic Annealing

Optimized heating and cooling profiles during thermal annealing maximizes cross-linking to balance strength and flexibility. This is achieved by tailoring chain mobility.

With advanced materials and processes rapidly co-evolving, 3D printing shows immense promise for fabricating flexible components with unprecedented properties. These innovations are opening up new horizons across applications demanding high elasticity, durability, and geometrical compliance.