Measurement and simulation of the pull-off strength at the separation of miniaturized 3D connectors consisting of silicon masters with undercuts and PDMS replicas

Applications in various sectors of microtechnology such as MEMS, microfluidics, and lab on chip call for reliable low-cost joining approaches that are detachable and re-closable, providing a tight fit at the micron level. Dovetail-like structures are a promising approach to realize the female side of such connectors and moulding is a suitable technique to produce the counterpart that completes the joint. Force–displacement measurements were performed for 2 × 2 cm2 master-replica assemblies, prepared from Si and PDMS (polydimethylsiloxane) and featuring dovetail-like structures with different undercuts. For measurement a miniaturised force–displacement tester was set up. Maximum retention forces of up to about 60 mN per trench of 1 cm length were measured for lines with 11.5 μm wide undercuts. Finite element modelling using a linear elastic model was employed to simulate the local distribution of stress and strain in the PDMS under loading with an applied tensile force. The simulation results approximate the measurements well. The quantitative results obtained can be used for designing miniaturized connectors with undercuts.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Re-closable linear Si/PDMS connectors with dovetail-like undercuts were prepared. ► From force–displacement measurements maximum holding forces are extracted. ► Forces, displacements and stresses were FEM-simulated using a linear elastic model. ► The simulation results are in good agreement with the experiments. ► The methods and results allow design estimations of undercut connectors for MEMS.