Rogers et al.
[48][1] were the first to propose a kinetically controlled transfer printing method. This method uses velocity to dynamically control the adhesion force switching between interfaces to achieve transfer printing, because of the adhesion characteristics of PDMS. The energy release rate
Gstamp/filmcrit of the seal/ink interface depends on the layering speed ν, while the energy release rate
Gstamp/filmcrit of the ink/target substrate interface is independent of velocity. The main process of kinetic control transfer is as follows: The ink is extracted from the donor substrate by using the adhesion characteristics of the seal through a relatively large stripping speed (about 10 cm/s, i.e.,
Gfilm/substratecrit<Gstamp/filmcrit [78][2]). The seal and ink are contacted with the target substrate, and the seal is extracted at a relatively small stripping speed (about 1 mm/s, i.e.,
Gfilm/substratecrit>Gstamp/filmcrit [78][2]). Additionally, the ink is transferred to the target substrate.
Figure 31a,b shows the mechanical model diagrams of the extracting film and printing film processes. Feng et al.
[78][2] regarded the seal/substrate interface separation as a steady-state crack propagation process.
Figure 31c shows the schematic diagram of the seal interface separation when subjected to a vertical upward pull F. The energy release rate is
where
G is the energy release rate,
F is the tensile force, and
w is the width of the seal. Formula (2) is the energy release rate of the seal/film interface, which is
where
G0 is the critical energy release rate, ν is the stripping speed,
ν0 is the reference stripping speed, and
n is the scaling parameter determined during the experiment. Formula (2) applies to various stripping speed ranges, temperature ranges, metal/polymer interfaces, polymer/polymer interfaces, and so forth.
Figure 31d shows a graph of the relationship between energy release rate and stripping speed, where
νmax is the maximum stripping speed and
ν is the critical stripping speed. The critical speed depends on the stiffness of the seal. Under the condition of determining the geometric dimension of the seal, the critical speed decreases with the decrease in the modulus of the seal
[78][2]. Feng et al.
[78][2] also studied the effect of temperature on the transfer printing structure, which found that low temperatures favored the extraction of the ink and high temperatures favored the transfer printing. Also explored is the discontinuous film, both discrete of distribution ink. The relation between average energy release rate and contact area is
where ƒ represents the contact area fraction (0 < ƒ < 1) of the seal/ink interface, where
Gink/stamp(ν) is the energy release rate. Formula (3) shows that the adhesion strength between the seal/ink/target substrate interfaces is proportional to the contact area. Kim et al.
[71][3] conducted a 90° stripping experiment on this basis and concluded that reducing the contact area was beneficial to improve the success rate of transfer printing.
Figure 42a shows the relationship between the percentage of the seal contact area and the percentage of the successful transfer area. Jiang et al.
[37][4] also conducted an experimental investigation and simulations on seal transfer printing Si tapes with different stripping speeds. It was found that the transfer printing efficiency increases with the increase in the stripping speed, but the transfer printing efficiency increases slowly when the stripping speed is greater than 100 mms
−1.
Figure 42b shows the optical image of the transferred Si tape under different stripping speeds of the PDMS seal, and
Figure 42c shows a graph of transfer printing efficiency versus stripping speed in the simulation experiment. The simulation results are consistent with the experimental results.
Since the controllable range of bonding is narrow, in most situations, kinetic control transfer printing requires an adhesive to be applied above the target substrate to assist in the transfer printing process. However, this method cannot change the adhesive force of the seal and make the transfer printing process continuous, which greatly reduces the efficiency of the transfer printing. Kim et al.
[80][6] found that by changing the design parameters of the seal and adjusting the stripping speed, the controllable range of adhesion strength can be effectively extended, and also high yield manufacturing can be achieved.
Figure 53a,b shows graphs of the relationship between seal thickness and tensile force under different contact loads,
L=10 mN, L=100 mN,L=800 mN, at the stripping speeds
Vsep=2 μm/s and
Vsep=500 μm/s, respectively. The results show that the stripping force is correlated with the critical interface contact area, and the thicknesses of the seal, contact load, and stripping speed are the main influencing factors. Liang et al.
[70][7] established a tensile force model in which the stripping speed and pretightening force were considered. Finally, the relationship between stripping speed, pretightening force, and tensile force was studied. From
Figure 53c, we can know that the tensile force increases with the increase in peeling speed at a certain preload. From
Figure 53d, we can know that the tensile force increases with the increase in pretightening force at a certain stripping speed. It follows that a larger preload force should be applied during the transfer extraction phase, and a smaller preload force should be applied during the printing phase, which can play a significant role in improving the transfer printing output. Through analysis of the theoretical model and experimental data, the results show that the pretightening force at a large stripping speed has a greater influence on the tensile force than the pretightening force at a small stripping speed
[70][7].
Figure 53e,f shows examples of transfer printing on cylindrical glass lenses and PET substrates using the kinetic control transfer printing method.
The process of kinetic control transfer printing is simple and easy to operate, but the stripping speed control adhesion strength range is limited, the transfer printing is greatly restricted, and its durability depends on the preparation of the target substrate and the cleanness and flatness of the substrate surface. This method is also not applicable to target substrates of viscous materials. Therefore, its application is limited by different materials. Precise speed control is required during operation, which requires a speed control device to improve transfer printing efficiency, but greatly increases the cost of the transfer printing. Moreover, this transfer printing method has not produced an example of nanotransfer printing because the energy release rate is influenced by the contact area.