3D Bioplotter Research Papers

Inks containing sub-20 µm particles of doped bismuth telluride (n-type Bi2Te2.73Se0.3 or p-type (Bi0.5Sb1.5)Te3) are extruded into 330 µm diameter filaments. When solid-state sintered up to 857 K under no pressure, the filaments only partially densify, with over 20% porosity remaining. Coating the filament with TeO2 powder, followed by hydrogen reduction to liquid Te, enables liquid phase sintering at 710 K, with rapid densification to less than 5% porosity within 1 h. Coating with a stoichiometric blend of Bi2O3 + 3TeO2 powders, followed by hydrogen reduction to liquid Bi and Te, provides transient liquid phase sintering at 808 K and subsequent reaction to Bi2Te3, resulting in fast filament densification,…

Insulating polymer composites with conductive filler particles are attractive for sensor applications due to their large piezoresistive response. Composite samples composed of a polymer matrix filled with particles of doped semiconductor that gives a piezoresistive response that is 105 times larger than that of bulk semiconductor sensors are prepared here. The piezoresistance of such composite materials is typically described by using a tunneling mechanism. However, it is found that a percolation description not only fits prior data better but provides a much simpler physical mechanism for the more flexible and soft polymer composite prepared and tested in this study. A…

Whereas the rigid nature of standard thermoelectrics limits their use, flexible thermoelectric platforms can find much broader applications, for example, in low-power, wearable energy harvesting for internet-of-things applications. Here we realize continuous, flexible thermoelectric threads via a rapid extrusion of 3D-printable composite inks (Bi2Te3 n- or p-type micrograins within a non-conducting polymer as a binder) followed by compression through a roller-pair, and we demonstrate their applications in flexible, low-power energy harvesting. The thermoelectric power factors of these threads are enhanced up to 7 orders-of-magnitude after lateral compression, principally due to improved conductivity resulting from reduced void volume fraction and partial…