Creating 3D printed sensor systems with conductive composites

Abstract

Fused filament fabrication (FFF), the printing of parts through the deposition of layers of melted thermoplastic, is one of the most widely used 3D printing processes due to its ease of use, low cost and accessibility. In this work, integration of 3D printed sensors and interconnect between embedded components into a printed part is demonstrated in an FFF process for the first time. The use of printed active materials for sensing allows interactivity with the end user through mechanisms like touch and temperature. Through dual extrusion in a low cost commercial printer, printing of both a conductive thermoplastic composite and a non-conducting filament are combined to create complex patterns. The piezoresistive and thermally responsive properties of the thermoplastic composite are used to create several different sensor modalities including a piezoresistive strain sensor, a contact switch and a resistive temperature sensor. A heated insertion technique is then developed for embedding of electrical components. The conductive thermoplastic is also used to incorporate a 3D printed circuit board in the same part, including in-line embedding within the body of the part during the printing process. The sensor performance and component embedding properties are characterized, and the process is used to print systems including relaxation oscillators and op-amp interface circuits for sensor monitoring.

Multiple Reprocessing of Conductive PLA 3D-Printing Filament: Rheology, Morphology, Thermal and Electrochemical Properties Assessment

“…The filaments made of materials with high electrical conductivity has found particular interest in electronics. The commercially available conductive polylactic acid (PLA) filament is used to print electrical circuits and simple sensors such as temperature, stress and touch sensors [ 8 ]. In this field, the focus has been placed especially on the development of new conductive filaments that exhibit better mechanical properties while obtaining higher conductivity [ 9 , 10 ].…”

Laser Direct Structured 3D Circuits on Silicone

“…Another property of silicone is its low surface energy, which causes liquids to readily bead up on silicone surfaces, making it popular for waterproof coatings. ,− Silicones rank among the lowest adhesion materials, with surface energies comparable to Teflon . Because of the low surface energy, it is difficult for conductive inks in processes, such as direct ink writing (DIW), to be applied and adhere to silicone surfaces. ,, Much research has been done on silicone-based devices using liquid conductors encapsulated within silicone channels, with limitations on incorporating circuit components and circuit complexity. ,,− An alternative is to use a flexible conductive ink that is compatible (has an equal or lower surface tension) with the elastomeric substrate. , However, the conductivity of these inks is often low; low conductivity results in lossy circuits and inefficient antennas or low- Q magnetic components. ,,− …”

Printed flexible mechanical sensors

“…For instance, various types of mechanical sensors (e.g., force, [33][34][35] pressure, [36][37][38][39][40] and strain [41][42][43][44][45][46] ) can be produced by leveraging many 2D/3D printing techniques including but not limited to screen printing, [47][48][49][50][51] inkjet printing, [52][53][54][55][56] direct ink writing (DIW), [57][58][59] digital light processing (DLP), [60][61][62] and fused filament fabrication (FFF). [63][64][65][66] The additive nature of printing technologies also largely reduces the fabrication cost and time; 67,68 in addition, fabrication by printing enabled the production of flexible mechanical sensors with excellent performance. Currently, some of the printed flexible mechanical sensors have demonstrated their unique applications in fields such as healthcare, robotics, etc.…”