have all been reported. [2][3][4][9][10][11][12][13][14][15][16] The more popular methods of AFM and nanoindentation can provide accurate forcedisplacement information, which has been used to study mechanical behavior of the structures. [9,15] With growing interest in using DLW across many different disciplines, additional methods for dynamic control of these structures are needed. For example, tunable IR metamaterials that exhibit a change in optical response with mechanical strain have been reported. [17][18][19] In addition to optical metamaterials, DLW structures have been used as cell scaffolding to study the effects of short-term mechanical loading on cell behavior and development. [10,15] It would be beneficial to develop an alternative platform that provides comparable sensitivity for testing such devices.Here, we introduce a noncontact technique to manipulate soft 3D DLW microstructures through integration with existing micro-electromechanical systems (MEMS) technology. Structures were fabricated by DLW directly on electrostatic and thermal MEMS actuators. These reproducible MEMS devices were made using a cost-effective commercial foundry process and can be electrically controlled with high-precision displacement (≈1 nm) under ambient conditions. [20] DLW operates by focusing a femtosecond laser in a volume of liquid photoresist to induce two-photon absorption (TPA) events. TPA initiates a polymerization reaction within this laser focal region that results in the formation of a solid, vertically oriented, ovoid volumetric pixel (voxel). We use a commercial 780 nm DLW system (Nanoscribe Photonic Professional GT) which can achieve 200 nm resolution in the x-y plane with a voxel aspect ratio (axial diameter/lateral diameter) of approximately 3 using a microscope objective with a numerical aperture of 1.4. [21] With our system, laser focal-spot position can be controlled using either high-speed (≈1 cm s −1 ) galvo-scanning mirrors or, for intricate microstructures that require high accuracy instead of high speed, a 3-axis piezo system. DLW differs from single-photon absorption stereolithography because there is no need to stack exposed resist layers. By moving the laser focal spot around within the photoresist and selectively crosslinking only within this focal spot, complex 3D structures can be polymerized according to the beam path. DLW systems allow rapid prototyping of submicron-resolution structures that would otherwise be impossible to fabricate via single-photon stereolithography or the deposition and etching processes commonly used in semiconductor foundries.Direct laser writing (DLW) is an advanced fabrication technique that allows users to create complex 3D microstructures from polymer precursors. These microstructures can be integrated with micro-electromechanical systems (MEMS) actuators. MEMS actuators provide a convenient platform for interacting with the intricate microstructures, either to characterize their mechanical properties or cause them to deform. Structures are fabricated directly ont...

We developed an organ-on-a-chip platform with integrated stimulators and sensors. The platform is fabricated using direct laser writing (DLW) and allows for generation and study of functional 3D cardiac microtissues in controlled microenvironments.

Cell migration, critical to numerous biological processes, can be guided by surface topography. Studying the effects of topography on cell migration is valuable for enhancing our understanding of directional cell migration and for functionally engineering cell behavior. However, fabrication limitations constrain topography studies to geometries that may not adequately mimic physiological environments. Direct Laser Writing (DLW) provides the necessary 3D flexibility and control to create well-defined waveforms with curvature and length scales that are similar to those found in physiological settings, such as the luminal walls of blood vessels that endothelial cells migrate along. We find that endothelial cells migrate fastest along square waves, intermediate along triangular waves, and slowest along sine waves and that directional cell migration on sine waves decreases as sinusoid wavelength increases. Interestingly, inhibition of Rac1 decreases directional migration on sine wave topographies but not on flat surfaces with micropatterned lines, suggesting that cells may utilize different molecular pathways to sense curved topographies. Our study demonstrates that DLW can be employed to investigate the effects and mechanisms of topography on cell migration by fabricating a wide array of physiologically-relevant surfaces with curvatures that are challenging to fabricate using conventional manufacturing techniques.