Investigations on the Adhesive Contact Behaviors between a Viscoelastic Stamp and a Transferred Element in Microtransfer Printing

Abstract

Microtransfer printing is a sophisticated technique for the heterogeneous integration of separately fabricated micro/nano-elements into functional systems by virtue of an elastomeric stamp. One important factor influencing the capability of this technique depends on the adhesion between the viscoelastic stamp and the transferred element. To provide theoretical guidance for the control of adhesion in the transfer printing process, a finite element model for the viscoelastic adhesive contact between a polydimethylsiloxane (PDMS) stamp and a spherical transferred element was established, in which the adhesive interaction was modeled by the Lennard-Jones surface force law. Effects of the unloading velocity, preload, and thermodynamic work of adhesion on the adhesion strength, characterized by the pull-off force, were examined for a loading-dwelling-unloading history. Simulation results showed that the unloading path deviated from the loading path due to the viscoelastic property of the PDMS stamp. The pull-off force increased with the unloading velocity, and the increasing ratio was large at first and then became low. Furthermore, the influence of the preload on increasing the pull-off force was more significant under larger unloading velocity than that under smaller unloading velocity. In addition, the pull-off force increased remarkably with the thermodynamic work of adhesion at a fixed maximum approach.

On the Long and Short-Range Adhesive Interactions in Viscoelastic Contacts

“…In addition, Van Dokkum et al [18] observed, in a similar problem, the normalized effective surface energy Δ ef f ∕Δ (or equivalently FPO ) decreases with the Tabor parameter. Furthermore, Jiang et al [19], performing FE calculations on the pull-off force of a spherical indenter from a soft viscoelastic stamp, observed a reduction of FPO when decreasing Δγ . Similarly to our approach, they changed the value of Δγ maintaining the same maximum penetration max .…”

Size effects in adhesive contacts of viscoelastic media

“…In such case, the substrate is in a fully relaxed state at the end of the loading phase. Notice the same condition can be reached by loading at nonzero velocity and waiting a sufficient long dwell time (t 0 → ∞) before unloading [11,19]. If unloading is then performed at nonzero V , the maximum pull-off force F PO(max) , which is asymptotically reached at high contact line velocities V c = −da/dt [9], should be…”

“…In a recent work, Jiang et al [19] developed a finite element model for the viscoelastic adhesive contact between a PDMS stamp and a sphere. In their simulations, unloading starts from a relaxed state of the viscoelastic stamp.…”

On the long and short-range adhesive interactions in viscoelastic contacts

“…Furthermore, Jiang et al [17], performing FE calculations on the pull-off force of a spherical indenter from a soft viscoelastic stamp, observed a reduction of FPO when decreasing ∆γ.…”