Microthermoforming of microfluidic substrates by soft lithography (µTSL): optimization using design of experiments

Abstract

We present a detailed analysis of microthermoforming by soft lithography (μTSL) for replication of foil-based microfluidic substrates. The process was systematically optimized by design of experiments (DOE) enabling fabrication of defect-free lab-on-a-chip devices. After the assessment of typical error patterns we optimized the process toward the minimum deviation between mold and thermoformed foil substrates. The following process parameters have most significant impact on the dimensional responses (p < 0.05): critical temperature before start of evacuation, molding temperature, pressure of pre-stretching and duration of pre-stretching as well as duration of molding pressure. The most relevant parameter is molding temperature with >40% relative impact. The DOE results in an empirical process model with a maximum deviation between the prediction and experimental proof of 2% for the optimum parameter set. Finally, process optimization is validated by the fabrication and testing of a microfluidic structure for blood plasma separation from human whole blood. The optimized process enabled metering of a nominal volume of 4.0 μl of blood plasma with an accuracy deviation of 3% and a metering precision of ±7.0%. The μTSL process takes about 30 min and easily enables the replication of 300 μm wide microchannels having vertical sidewalls without any draft angles in a well-controllable way. It proves to be suitable for multiple applications in the field of microfluidic devices.

Point-of-Care System for HTLV-1 Proviral Load Quantification by Digital Mediator Displacement LAMP

“…The microfluidic LabDisk cartridges were manufactured by soft lithography in the Hahn–Schickard prototyping facilities [ 21 ]. In brief, the master tool for replication was manufactured out of Plexiglas poly(methyl methacrylate) (PMMA) (Evonik, Darmstadt, Germany) on a KERN Evo mill (KERN Microtechnik, Eschenlohe, Germany).…”

RespiDisk: a point-of-care platform for fully automated detection of respiratory tract infection pathogens in clinical samples

“…1. Processes for RespiDisk fabrication comprise the thermoforming of the RespiDisk from a polycarbonate (PC) film, 32 loading with assay reagents (Table 1), sealing with a pressure-sensitive adhesive film (9795R, 3 M, USA) and packaging in an aluminium pouch filled with nitrogen and desiccant.…”

Untersuchungen zum Mikrothermoformen von Polycarbonat-Folien und zu dessen Integration in den Spritzgießprozess

“…Es handelt sich um eine Variation aus Vakuum-oder Druckluft-Negativumformung, die abgeleitet wurde vom Trapped-Sheet-Thermoformen [11]. Die Folie wird hierbei in einem zweiteiligen, abgedichteten Werkzeug platziert, der Umformbereich nach dem Schließen des Werkzeugs evakuiert und die Folie über Kontaktheizung mit dem Werkzeug auf Umformtemperatur erwärmt [10,[12][13][14]. Der Umformvorgang erfolgt durch das Einleiten eines komprimierten Gases, in der Regel Stickstoff, mit absolutem Druck von 1 bis zu 40 [12,15] bzw.…”

“…Im Unterschied zum Spritzgießen entsteht das Bauteil primär durch Dehnung mit maximalen Hencky-Dehnraten von bis zu 25 s -1 [6]. In den letzten 15 [8,9] oder als mikrofluidische Chips [10]. Denkbar sind ferner Anwendungen im Bereich der Medizintechnik, Optik oder als Elektronikkomponenten.…”