High Precision 3D Printing for Micro to Nano Scale Biomedical and Electronic Devices

Abstract

Three dimensional printing (3DP), or additive manufacturing, is an exponentially growing process in the fabrication of various technologies with applications in sectors such as electronics, biomedical, pharmaceutical and tissue engineering. Micro and nano scale printing is encouraging the innovation of the aforementioned sectors, due to the ability to control design, material and chemical properties at a highly precise level, which is advantageous in creating a high surface area to volume ratio and altering the overall products' mechanical and physical properties. In this review, micro/-nano printing technology, mainly related to lithography, inkjet and electrohydrodynamic (EHD) printing and their biomedical and electronic applications will be discussed. The current limitations to micro/-nano printing methods will be examined, covering the difficulty in achieving controlled structures at the miniscule micro and nano scale required for specific applications.

Keywords: 3D printing; biomaterial; electronics; micro/nano scale printing.

Figure 7

(a) Photograph of inkjet printing of EGaInNPs, scale bar: 5 mm [131]. (b) EHD printed circuit pattern on glass slide (left), scale bar: 500 µm; Healed conductor remained conductive when bended by hand (right) [65]. (c) SEM images of 3D pillar structures [173]. (i) Schematic illustration of 3D pillar printing. (ii) Printed Ag pillar. Scale bar, 2 μm. (iii) Printed Cu pillar. Scale bar, 5 μm. (iv) Printed Co pillar. Scale bar, 5 μm. (v) Printed anthracene pillar. Scale bar, 5 μm. (vi) Cross-shaped array of five anthracene pillars. Scale bar, 10 μm. (vii) Letter “E”-shaped array of anthracene pillars. Scale bar, 10 μm. (viii) “UNIST”-shaped array of Cu and anthracene pillars. Black and white pillars in the array are composed of anthracene and Cu, respectively. Scale bar, 10 μm.

Figure 9

(a) Photograph of hand-shaking wearing the PDMS tactile sensing glove (left); Schematic of the PDMS tactile sensing glove (right) [218]. (b) Schematic of the process for fabricating fully printed graphene photodetector devices using the mask-free direct-writing method [214]. (c) flexible composite pressure sensors for underwater monitoring (left); pulse wave curves and response signals under different conditions (right [151]). (d) Photographs of the increased light intensity (circuit voltage was 3 V) after NIR light exposure (top); Pressure-dependent conductivity of PNIPAM/ Laponite/CNT hydrogels (bottom) [234].

Figure 1

Overview of micro/nano scale printing processes and applications that have been 3D printed from 500 nm to 50 µm via lithography, inkjet and EHD printing [18].

Figure 2

Illustrations of various 3D printing processes showing (a) stereolithography, (b) dip pen nanolithography (c) Inkjet printing and (d) EHD printing [22].

Figure 3

EHD printing principle and modes. (a) EHDP printing system. (b) Cone formation and force analysis. (c) EHD jet modes.

Figure 4

(a) Relationship between EHD jetting state and applied voltage (colorful images are meniscus shape at the same calculating moment (t = 0.4 ms) in 2.0 kV and 2.5 kV, respectively) [86]. (b) EHD jetting states change with the variations of applied voltage and flow rate when other parameters are certain values [94]. (E4T6, dimensionless velocity (χ) = 2.62, permittivity (ε′) = 14.0, d/L is the ratio of nozzle diameter (d) and nozzle–counter electrode distance (L), Tq/Th is the ratio of two characteristic times that determine the jetting system). (c) Map of printing capabilities in terms of printing speed and feature size for EHDP technologies providing submicron resolution [95]. (d) EHD jet modes at different flow rate Q, working distance Z, and applied voltage V [96].

Figure 5

(a) Viscosity of PEDOT: PSS inks as a function of PEDOT: PSS nanofibril concentration (left); Shear yield stress of inks as a function of PEDOT: PSS nanofibril concentration (right) [104]. (b) Images of re-dispersed suspensions with varying PEDOT: PSS nanofibril concentration [104].

Figure 6

(a) Flat needle and angular needle (θ = 60°) [107]. (b) Tip-assisted EHD [115]. (c) EHDP with the added metal ring [116]. (d) core-shell printing [123]. (e) Janus printing [88]. (f) Multi-cores printing [124].

Figure 8

Biomedical applications of micro/nano 3D printed devices [8,176].