TY - THES

T1 - On the demolding of micro-structured surfaces for medical applications

AU - Struklec, Tobias

N1 - embargoed until 28-03-2016

PY - 2011

Y1 - 2011

N2 - This thesis is a theoretical study on the demolding of micro structured polymer surfaces in hot embossing and injection molding. Many replication problems, e.g. ripping or deformation of the micro structure, can affect the final part quality. These problems arise due to the lack of understanding the underlying mechanisms. Therefore, demolding force was introduced as a representing value for the demoldability of micro structured surfaces. Subsequently, the mechanisms for demolding are studied leading to an overview of main influencing factors. These – geometry, material, mold and process – are studied regarding their impact on demoldability. Furthermore, this thesis tries to link these influencing factors to the demolding problems as well as to the local physical mechanisms, i.e. adhesion, friction and stress distribution. Based on this theoretical background the design of the microstructure for a test chip is discussed, taking into account the theoretical study. The specifications for this test chip try to minimize secondary influences, like hindered shrinking of the micro structures due to geometrical inhibition. Additionally, a test plan is devised to examine the correlation of different coatings to the demolding force. This will allow selecting appropriate coatings for different processes and should give insight into the interactions of different polymers with different metal based or fluorine based coatings.

AB - This thesis is a theoretical study on the demolding of micro structured polymer surfaces in hot embossing and injection molding. Many replication problems, e.g. ripping or deformation of the micro structure, can affect the final part quality. These problems arise due to the lack of understanding the underlying mechanisms. Therefore, demolding force was introduced as a representing value for the demoldability of micro structured surfaces. Subsequently, the mechanisms for demolding are studied leading to an overview of main influencing factors. These – geometry, material, mold and process – are studied regarding their impact on demoldability. Furthermore, this thesis tries to link these influencing factors to the demolding problems as well as to the local physical mechanisms, i.e. adhesion, friction and stress distribution. Based on this theoretical background the design of the microstructure for a test chip is discussed, taking into account the theoretical study. The specifications for this test chip try to minimize secondary influences, like hindered shrinking of the micro structures due to geometrical inhibition. Additionally, a test plan is devised to examine the correlation of different coatings to the demolding force. This will allow selecting appropriate coatings for different processes and should give insight into the interactions of different polymers with different metal based or fluorine based coatings.

KW - lab on a chip

KW - demolding

KW - injection molding

KW - micro structures

KW - demolding force

KW - medical applications

KW - Lab on a chip

KW - Mikrostrukturen

KW - Entformen

KW - Spritzguß

KW - Entformungskraft

KW - Medizintechnik

M3 - Master's Thesis

ER -