Intermittent Embedding of Wire into 3D Prints for Wireless Power Transfer

Abstract

3D printing is rapidly moving into the realm of electronics and fully functioning devices. These devices include 3D printed plastic parts with conductive materials embedded in the plastic using additive manufacturing techniques to produce functioning circuits. However, current materials and techniques limit the amount of power that can be supplied to embedded circuits. The state of the art for embedding traditional conductive materials, such as solid metal wire, uses the continuous application of heat. Continuous heat often overheats and damages the previously printed layer of plastic material potentially ruining the part and device. Additionally, current devices with embedded electronics require either external power or embedded energy storage such as a battery. Both the continuous application of heat and the need for power affect design choices and can severely limit potential use cases of the device. This research presents analysis and demonstration of embedding traditional copper wires onto a plastic substrate using intermittent application of heat and pressure using a traditional Fused Filament Fabrication plastic print nozzle at specific points, herein referred to as embedding instances. Detailed analysis of the interaction of a heating element (print nozzle), metal wire, and plastic substrate are provided to give context for the new technology presented. High thermal conductivity in the wire conducts heat away from the heating element quickly, and continuous application of heat to the wire can melt the plastic substrate along the wire, damaging previously embedded sections of wire, especially at the start of the embedding process and after turning sharp corners while embedding the wire. Applying heat for short periods at intermittent locations is presented as a solution to this problem while still melting the plastic enough to produce the bonding necessary for the wire to be embedded into the previous printed layer of plastic substrate. This technique is then used to manufacture a pair of identical parts, each with an embedded antenna intended for wireless power transfer. Once the first layer of wire antenna is embedded, additional layers of plastic are deposited to embed the copper wire completely within the part. Four separate embedded antenna layers of embedded wire are connected to create a multi layered, multi coil antenna in two identical parts. Experiments were then run to prove the viability of wireless power transfer from one part to the other.

Appendix

In Fig. 15, $L$ is the distance between the embedded points and the maximum deflection occurs in the middle of the length.

$$L = 2l$$

(8)

When $l$ is the half of $L$, the stretched length of one side is $\Delta l$. A strain of the material in tension, $\upepsilon$ is defined as Eq. 9.

$$\upepsilon = \frac{\Delta l}{l}$$

(9)

Then the deflected length of a half side become $l(1+\upepsilon )$. When maximum allowed deflection is defined as ${\delta }_{allow}$, then it becomes the normal distance from origin line to the point of maximum deflection. By the Pythagorean theorem, it can be derived as Eq. 10.

$$\left( {l\left( {1 + \upepsilon } \right)} \right)^{2} = l^{2} + \delta_{allow}^{2}$$

(10)

After solving for $l$, the final equation is Eq. 11

$$l = \frac{\delta_{allow}}{{\sqrt { \upepsilon^{2} + 2 \upepsilon } }}$$

(11)