Technology of microthermoforming of complex three-dimensional parts with multiscale features

Abstract

Thermoforming parts with micro-scale design features require use of thin polymer films. Low heat capacity and fragility of thin (\100 lm) polymer films requires new technical developments for precise heating and form pressure application. This paper will present results of an improved process based on a new replication machine. Temperature stability and pressure distribution is highly improved, even at reduced cycle times. With an upgraded temperature range microthermoforming of high temperature polymers is possible. This technology is well suited for the replication of three-dimensional micro parts with multiscale features. Replication of hollow parts with multiscale features is also possible. Outer dimension in macroscopic length scale and functional design features in microscopic length scale are combined with nanoscale surface structures in an affordable technology.

Mimicking the biological world: Methods for the 3D structuring of artificial cellular environments

“…This process is driven in the range of the glass transition temperature of the used polymer. Melting of the polymeric blank is avoided, so prestructured blanks can easily be facilitated [41]. Often the generation of moulds for thermoforming is easier compared to hot embossing tools.…”

“…One possible way to realize these complex multiscale structures is to thermoform premanufactured submicron and nanostructured foil. The resolving structures which includes hydrophobic and hydrophilic areas could be utilized for spatially guided cell adhesion [41]. Different types of materials processed together through microthermoforming lead to wide distribution of surface properties.…”

“…Currently limits are set by the lack of suitable dropon-demand devices, biocompatibility of polymers, and by long process times. Nevertheless, the fusion of different disciplines is [41] Poly(ethyleneoxide terephthalate)-poly (butyleneterephthalate) (PEOT/PBT) copolymers [18] • Multiphoton polymerization of hydrogels/ polymers [42][43][44] -Inkjet printing -Organ printing [15,[45][46][47] Biofunctionalization of 3D substrates Chemical functionalization by patterning [48][49][50][51][52][53] Patterning of hydrogels [16,17,54] Biological application…”

Process windows of ultrasonic thermoforming of micro structures

“…Since 1999 several working groups have been showing to which extend thermoforming can also be applied for generating micro structures on polymer layers (Dreuth and Heiden 1999;Truckenmüller et al 2002Truckenmüller et al , 2008Truckenmüller et al , 2011Gieselbrecht et al 2006;Focke et al 2009Focke et al , 2010Schmidt et al 2011;Heilig et al 2011;Nagarajan and Yao 2011;Jungmeier 2015). The cycle times of these processes are on the order of some minutes because the entire tool needs to be heated up to the softening temperature of the thermoplastic foil and cooled down again below that temperature.…”

Integration of moth-eye structures into a poly(dimethylsiloxane) stamp for the replication of functionalized microlenses using UV-nanoimprint lithography

“…9 However, the wavelength dependence of the refractive index makes it difficult to obtain a broadband antireflective effect. 15,16 In contrast to these works, the thermoforming process is not used for the fabrication of structured foils as a final product, but as an intermediate lithography step for the fabrication of a 3D structured PDMS stamp for UV-NIL. 10 The surface relief of the moth-eye structure results in a gradual change of the refractive index from one medium to another.…”