Cell adhesion is important to develop cell microarrays and biocompatible materials. Collagen has been reported to be able to improve cell adhesion. In this paper, two collagen coating methods (collagen grafted directly on the substrate and chitosan-modified substrate) were carried out, on which the adhesive behaviors of HeLa cells were studied. An atomic force microscope and a surface potential meter were used to characterize morphologies and electric polarization of these surfaces. It was found that surface electric polarization and the its durability and surface topography were key factors to cell adhesion. Collagen (1 mg/mL) grafted on 1% chitosan-modified surface showed the best adhesion of HeLa cell. This work might be helpful to the practical application of cell microarray chips.

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We experimentally demonstrate that multiple microcombs can coexist in monochromatically pumped Si3N4 microresonators. By pumping around the mode crossing using a CW laser with mixed polarization, three types of coherent microcombs are generated simultaneously: (i) TE-polarized soliton microcomb; (ii) TM-polarized Turing rolls microcomb; and (iii) cross-phase-modulation-induced TM-polarized microcomb. It is proved that the type-(iii) microcomb shares the same comb line spacing with the type-(i) microcomb although the free spectral ranges of TE and TM modes are different. In addition, a 22.95-GHz signal is extracted from a ∼100-GHz microresonator by heterodyning the TE and TM comb lines, and phase noise analysis reveals their coherence characteristics.

Dual-coupled structure is typically used to actively change the local dispersion of microresonator through controllable avoided mode crossings (AMXs). In this paper, we investigate the switchability of dissipative cnoidal waves (DCWs) based on dual-coupled microresonators. The switching dynamics of DCWs are numerically simulated using two sets of nonlinear coupled-mode equations. It is found that the pulse number of DCWs can only be decreased (i.e. switched unidirectionally) when working as perfect soliton crystals and can either be decreased or increased (i.e. switched bidirectionally) when working as Turing rolls. Moreover, the stable regions of DCWs can be greatly expanded due to the existence of AMXs. The switchability of DCWs would further liberate the application potential of microcombs in a wide range of fields, including frequency metrology, optical communications, and signal-processing systems.