Biocompatible Nanocapsules for Self-Healing Dental Resins and Bone Cements.

Bone cements and dental resins are methacrylate-based materials that have been in use for many years, but their failure rates are quite high with essentially all dental resins failing within 10 years and 25% of all prosthetic implants will undergo aseptic loosening. There are significant healthcare costs and impacts on quality of life of patients. Self-healing bone cements and resins could improve the lifespan of these systems, reduce costs, and improve patient outcomes, but they have been limited by efficacy and toxicity of the components. To address these issues, we developed a self-healing system based on a dual nanocapsule system. Two nanocapsules were synthesized, one containing an initiator and one encapsulating a monomer, both in polyurethane shells. The monomer used was triethylene glycol dimethacrylate. The initiator capsules synthesized contained benzoyl peroxide and butylated hydroxytoluene. Resins containing the nanocapsules were tested in tension until failure, and the fractured surfaces were placed together. 33% of the samples showed self-healing behaviors to the point where they could be reloaded and tested in tension. Furthermore, the capsules and their components showed good biocompatibility with Caco-2 cells, a human epithelial cell line suggesting that they would be well tolerated in vivo.

Thermoelectric properties enhancement of p-type composite films using wood-based binder and mechanical pressing.

Thermoelectric generators (TEGs) fabricated using additive manufacturing methods are attractive because they offer the advantages of scalability, lower cost, and potentially higher power density than conventional TEGs. Additive manufacturing of TEGs requires active thermoelectric particles to be dispersed in a polymer binder to synthesize printable slurries, and printed films to be subsequently subjected to a long and high temperature curing to enhance their thermoelectic properties. A large amount of polymer binder present in composite films results in a sizable loss in the electrical conductivity. In addition, a long and high-temperature film curing results is a slow and energy intensive fabrication process. In this work, we demonstrate the feasibility of using a small amount (≤10-3 wt ratio) of novel nanofiber cellulose (NFC) as a binder to provide sufficient adhesion strength to hold the TE particles together in the composite films. We also demonstrate a pressure induced densification process to enhance the thermoelectic properties of printed composite films. This novel approach has the potential to fundamentally transform the manufacting method for printing TEGs by eliminating the need of long-duration and high-temperature curing. A higher applied pressure leads to a compact packing and densification of films resulting in an improvement in the electrical conductivity. The highest power factor achieved for best performing p-type thermoelectric-NFC composite film subjected to pressure induced densification is 611 µW/m-K2.