Single-Cell Response to the Rigidity of Semiconductor Nanomembranes on Compliant Substrates

Abstract

Single-crystalline semiconductor nanomembranes (NMs) bonded to compliant substrates are increasingly used for biomedical research and in health care. Nevertheless, there is a limited understanding of how individual cells sense the unique mechanical properties of these substrates and adjust their behavior in response to them. In this work, we performed proliferation assays, cytoskeleton analysis, and focal adhesion (FA) studies for NIH-3T3 fibroblasts on 220 and 20 nm single-crystalline Si on polydimethylsiloxane (PDMS) substrates with an elastic modulus of ∼31 kPa. We also characterized cell response on bulk Si as a reference. Our in vitro studies show that varying the thickness of the NM between 20 and 220 nm affects the proliferation rate of the cells, their cytoskeleton, fiber organization, spread area, and degree of FA. For example, cultured cells on 220 nm Si/PMDS exhibit the same response as on bulk Si, that is, they are well-spread with a pentagonal (or dendritic) shape and show a good organization of stress fibers and FAs. On the other hand, the cells on 20 nm Si/PDMS are spherical, with fiber organization and FAs in undetectable levels. We explained the results of our in vitro studies through a shear-lag mechanical model. The calculated FA−substrate contact stiffnesses for fibroblasts on bulk Si and 220 nm Si/PDMS closely match, and they are significantly higher than the stiffness of the integrin clutches and the plaque. Conversely, focal contacts with 20 nm Si/PDMS have comparable lateral compliance to adhesionmediating intracellular organisms. In conclusion, our work relies on recent advances in NM technology to fill a critical knowledge gap about how individual cells sense and react to the mechanical properties of NM-based substrates. Our findings will have a major impact on the design of flexible electronic materials for applications in biomedical science and health care.

All‐Group IV Transferable Membrane Mid‐Infrared Photodetectors

“…[ 6 ] One of the key features is that thin membranes can be easily transferred and integrated onto flexible, curved, or transparent substrates of virtually any material, unlocking a range of new applications in inorganic flexible, stretchable, and wearable devices. [ 7 ] As a matter of fact, semiconductor membranes are currently used as versatile building blocks in a variety of applications in thermophotovoltaics, [ 8 ] single‐cell sensing, [ 9 ] pixellated solar cells, [ 10 ] light‐emitting diodes, [ 11 ] photodetectors (PDs), [ 12,13 ] and lasers. [ 14 ] The large‐scale integration using rolling‐based direct‐transfer printing method has paved the way to mass produce these high‐performance flexible and hybrid devices.…”