Effect of temperature on the SU‐8 photoresist filling behavior during thermal nanoimprinting

Abstract

SU‐8 photoresist is an ideal thermal‐imprinting polymer, which has been widely used in micro‐nano devices in recent years. However, the research on the filling behavior of SU‐8 photoresist during thermal nanoimprinting is not complete. In this paper, the stress relaxation curves and shear stress/rate flow curves were measured to analyze the temperature dependent rheological properties of SU‐8 photoresist. The filling behavior of SU‐8 photoresist was discussed based on thermal imprinting results at various temperatures. High‐precision nanochannels were fabricated with replication error of 2.8% at optimized thermal imprinting temperature of 85°C and duration of 10 min, which paves the way for high‐precision fabrication of SU‐8‐based micro‐nanofluidic chips.

Electrowriting of SU-8 Microfibers

“…After 90 min, the material’s rheological behavior turned unstable to print, showing frequent fiber pulsing [ 34 ] and irregular fiber diameter variance independent of stage translation speed. This is consistent with limitations found for MEW and the reported non-Newtonian properties of SU-8 when processed in melts [ 14 , 35 ]. Moreover, this approach allows for the processability of a thermoset polymer via MEW, which has not been reported in the past, as MEW is primarily dominated by thermoplastic polymers with low melting points [ 18 ].…”

“…These procedures yielded highly variable results, with fiber diameter expectedly decreasing with increased stage speed but lacking a discernible trend. This variability is attributed to the nature of SU-8, an epoxy-based resin that undergoes crosslinking with prolonged heat exposure, leading to changes in viscosity and overall rheological behavior that changes with the processing temperature ranges [ 13 , 14 ]. Consequently, a stable Taylor cone was challenging to achieve, resulting in frequent pulsing and the formation of highly tapered fibers (See Supplementary Materials Figure S1 ).…”

“…Process parameters that affect stability include temperature, applied voltage, mass flow through the nozzle, and collector speed, while the rheological behavior of the solution or melt can change due to physical or chemical changes that can result with time. Such is the case with SU-8, which is a thermoset material that crosslinks with applied heat, which is one of its main features as it alters its mechanical and rheological properties [ 12 , 13 , 14 ]. For adapting new polymers to MEW, these need to be determined before the creation of detailed and application-specific constructs [ 15 , 16 ].…”

Two‐Photon Polymerization Lithography for Optics and Photonics: Fundamentals, Materials, Technologies, and Applications

“…SU-8 is a low-cost material that needs to be heat-treated after polymerization, improving thermal stability in related applications. [186][187][188] Last but not least, it's transparent in the visible and highly resistant to traditional solvents, making it suitable for many applications such as microfluidic, [163] photonic (Figure 3d), [117] biomedical structures. [189]…”

Decrypting the thermal effects on the electric field-induced material formation process on Cr thin films

“…The average lifetime, reliability, and time to failure of various electrical and electromechanical systems depend on temperature [1]. Semiconductor device fabrication processes are also prone to changes in temperature and are thus carried out in a controlled ambience [2][3][4]. Scanning probe lithography (SPL) techniques are a new domain of nanolithography techniques which utilize the confinement of various physical phenomena under a sharp tip.…”