The interaction of mammalian cells with nanoscale topography has proven to be an important signaling modality in controlling cell function. Naturally occurring nanotopographic structures within the extracellular matrix present surrounding cells with mechanotransductive cues that influence local migration, cell polarization, and other functions. Synthetically nanofabricated topography can also influence cell morphology, alignment, adhesion, migration, proliferation, and cytoskeleton organization. We review the use of in vitro synthetic cell-nanotopography interactions to control cell behavior and influence complex cellular processes, including stem-cell differentiation and tissue organization. Future challenges and opportunities in cell-nanotopography engineering are also discussed, including the elucidation of mechanisms and applications in tissue engineering.

/pdf/engineering-substrate-topography-at-the-micro-and-nanoscale-4avksdy3cq.pdf

Engineering substrate topography at the micro- and nanoscale to control cell function.

Modulation of cell adhesion, proliferation and differentiation on materials designed for body implants.

Nanoimprint lithography (NIL) is a high throughput, high-resolution parallel patterning method in which a surface pattern of a stamp is replicated into a material by mechanical contact and three dimensional material displacement. This can be done by shaping a liquid followed by a curing process for hardening, by variation of the thermomechanical properties of a film by heating and cooling, or by any other kind of shaping process using the difference in hardness of a mold and a moldable material. The local thickness contrast of the resulting thin molded film can be used as a means to pattern an underlying substrate on wafer level by standard pattern transfer methods, but also directly in applications where a bulk modified functional layer is needed. Therefore it is mainly aimed toward fields in which electron beam and high-end photolithography are costly and do not provide sufficient resolution at reasonable throughput. The aim of this review is to play between two poles: the need to establish standard processes and tools for research and industry, and the issues that make NIL a scientific endeavor. It is not the author’s intention to duplicate the content of the reviews already published, but to look on the NIL process as a whole. The author will also address some issues, which are not covered by the other reviews, e.g., the origin of NIL and the misconceptions, which sometimes dominate the debate about problems of NIL, and guide the reader to issues, which are often forgotten or overlooked.

/pdf/nanoimprint-lithography-an-old-story-in-modern-times-a-2lq7ufuk7g.pdf

Nanoimprint lithography: An old story in modern times? A review

The phase-shifting mask consists of a normal transmission mask that has been coated with a transparent layer patterned to ensure that the optical phases of nearest apertures are opposite. Destructive interference between waves from adjacent apertures cancels some diffraction effects and increases the spatial resolution with which such patterns can be projected. A simple theory predicts a near doubling of resolution for illumination with partial incoherence σ < 0.3, and substantial improvements in resolution for σ < 0.7. Initial results obtained with a phase-shifting mask patterned with typical device structures by electron-beam lithography and exposed using a Mann 4800 10× tool reveals a 40-percent increase in usuable resolution with some structures printed at a resolution of 1000 lines/mm. Phase-shifting mask structures can be used to facilitate proximity printing with larger gaps between mask and wafer. Theory indicates that the increase in resolution is accompanied by a minimal decrease in depth of focus. Thus the phase-shifting mask may be the most desirable device for enhancing optical lithography resolution in the VLSI/VHSIC era.

Improving resolution in photolithography with a phase-shifting mask

Nanotopography-induced changes in focal adhesions, cytoskeletal organization, and mechanical properties of human mesenchymal stem cells

https://hal.archives-ouvertes.fr/hal-00291559/document

The motility of normal and cancer cells in response to the combined influence of the substrate rigidity and anisotropic microstructure

https://hal.archives-ouvertes.fr/hal-00374101/document

In vivo measurement of human brain elasticity using a light aspiration device.

The brain deformation that occurs during neurosurgery is a serious issue impacting the patient "safety" as well as the invasiveness of the brain surgery. Model-driven compensation is a realistic and efficient solution to solve this problem. However, a vital issue is the lack of reliable and easily obtainable patient-specific mechanical characteristics of the brain which, according to clinicians' experience, can vary considerably. We designed an aspiration device that is able to meet the very rigorous sterilization and handling process imposed during surgery, and especially neurosurgery. The device, which has no electronic component, is simple, light and can be considered as an ancillary instrument. The deformation of the aspirated tissue is imaged via a mirror using an external camera. This paper describes the experimental setup as well as its use during a specific neurosurgery. The experimental data was used to calibrate a continuous model. We show that we were able to extract an in vivo constitutive law of the brain elasticity: thus for the first time, measurements are carried out per-operatively on the patient, just before the resection of the brain parenchyma. This paper discloses the results of a difficult experiment and provide for the first time in-vivo data on human brain elasticity. The results point out the softness as well as the highly non-linear behavior of the brain tissue.

In vivo measurement of human brain elasticity using a light aspiration device

In nanoimprint lithography (NIL), one of the key points to be addressed is the printing uniformity on large area. During the process, the silicon mold undergoes significant mechanical stress of different kinds (tension, compression, flexion, and torsion). These stresses are function of the mold design and appear under the concurrent influence of both the applied pressure on the backside of the mold and an opposite force due to the polymer viscoelastic behavior. This translates into non-negligible deformations within patterned or unpatterned zones. This is a major issue because it causes nonuniformity of the printing, mold pattern break and degradation of the polymer surface. In this article, we demonstrate that during the imprint process mold deformations really occur at the local scale of the patterns but also at a larger scale.

Mold deformation in nanoimprint lithography

Of all phase shift mask techniques, the alternating type is both the best for improving resolution and the most difficult to use. The problems in its use include complicated design modifications, unwanted phase-transition printing and very challenging mask fabrication. This paper is the first report of a solution using an automatic shifter arrangement and a three-step phase-transition technique on etched-quartz alternating-type phase shift mask (PSM). The lithographic results as well as the electrical results presented demonstrate the feasibility of the technique for application to complex circuits and show the capabilities of this kind of mask in printing smaller dimension lines.

https://iopscience.iop.org/article/10.1143/JJAP.33.6779/pdf

Patrick Schiavone

Papers

The motility of normal and cancer cells in response to the combined influence of the substrate rigidity and anisotropic microstructure

In vivo measurement of human brain elasticity using a light aspiration device.

In vivo measurement of human brain elasticity using a light aspiration device

Mold deformation in nanoimprint lithography

Application of Alternating-Type Phase Shift Mask to Polysilicon Level for Random Logic Circuits