The ability to 3D print lithium ion batteries (LIBs) in an arbitrary geometry would not only allow the battery form factor to be customized to fit a given product design but also facilitate the use of the battery as a structural component. A major hurdle to achieving this goal is the low ionic conductivity of the polymers used for 3D printing. This article reports the development of anode, cathode, and separator materials that enable 3D printing of complete lithium ion batteries with low cost and widely available fused filament fabrication (FFF) 3D printers. Poly(lactic acid) (PLA) was infused with a mixture of ethyl methyl carbonate, propylene carbonate, and LiClO 4 to obtain an ionic conductivity of 0.085 mS cm −1 , a value comparable to that of polymer and hybrid electrolytes. Different electrically conductive (Super P, graphene, multiwall carbon nanotubes) and active (lithium titanate, lithium manganese oxide) materials were blended into PLA to determine the relationships among filler loading, conductivity, charge storage capacity, and printability. Up to 30 vol % of solids could be mixed into PLA without degrading its printability, and an 80:20 ratio of conductive to active material maximized the charge storage capacity. The highest capacity was obtained with lithium titanate and graphene nanoplatelets in the anode, and lithium manganese oxide and multiwall carbon nanotubes in the cathode. We demonstrate the use of these novel materials in a fully 3D printed coin cell, as well as 3D printed wearable electronic devices with integrated batteries.

Materials that retain a high conductivity under strain are essential for wearable electronics. This article describes a conductive, stretchable composite consisting of a Cu-Ag core-shell nanowire felt infiltrated with a silicone elastomer. This composite exhibits a retention of conductivity under strain that is superior to any composite with a conductivity greater than 1000 S cm. This work also shows how the mechanical properties, conductivity, and deformation mechanism of the composite changes as a function of the stiffness of the silicone matrix. The retention of conductivity under strain was found to decrease as the Young's modulus of the matrix increased. This was attributed to void formation as a result of debonding between the nanowire felt and the elastomer. The nanowire composite was also patterned to create serpentine circuits with a stretchability of 300%.

A water-based silver nanowire ink for the room temperature printing of highly conductive traces onto biological and nonplanar surfaces.

Interest in flexible, stretchable, and wearable electronics has motivated the development of additive printing to fabricate customizable devices and systems directly onto virtually any surface. However, progress has been limited by the relatively high temperatures (>200 °C) required to sinter metallic inks and time-consuming process steps, many of which require removal of the substrate from the printer for coating, washing, or sintering. In this work, we addressed these challenges and demonstrate carbon nanotube thin-film transistors (CNT-TFTs) that are fabricated by aerosol jet printing with the substrate never leaving the printer. The full in-place printing approach, from first step to last, used a maximum process temperature of only 80 °C on the printer platen. Silver nanowire (Ag NW) ink was found to be most viable for low-temperature, in-place sintering while still yielding good electrical interfaces to the CNT thin-film channels. These aerosol-jet printed Ag NW films were conductive immediately after fabrication, which is the key component enabling rapid and sequential in-place printing. The devices exhibit on-currents as high as 80 μA/mm, effective mobilities of 12 cm 2 /(V•s), and on/off current ratios exceeding 10 5 . These findings provide a promising path forward toward the additive manufacture of flexible and stretchable electronics in a low-cost, highly customizable, and agile manner.

Three-dimensionally-printed anthropomorphic physical phantom for mammography and digital breast tomosynthesis with custom materials, lesions, and uniform quality control region,"