Unlocking Spatial Surface Energy in Porous Skeletons: A Pathway to Bridging Electronic Circuits from 2D to 3D Architectures.

Conventional approaches to creating high-resolution electric circuits face challenges such as the requirement for skilled personnel and expensive equipment. In response, we propose an innovative strategy that leverages a photochemically modified porous polymer skeleton for in-situ circuit fabrication. By developing maskless surface energy manipulation that guides PEDOT:PSS-based conductive ink deposition, electric circuits with high precision, density, stability and adaptability are effortlessly engineered within or atop the porous skeleton, enabling transitions between 2D and 3D circuit configurations. This process simplifies prototyping while significantly reducing costs and maintaining efficiency, promising advancements across various technological sectors.

Substrate-Independent Maskless Writing of Functionalized Microstructures Using CHic Chemistry and Digital Light Processing.

Maskless photolithography based on digital light processing (DLP) is an attractive technique for the rapid, flexible, and cost-effective fabrication of complex structures with arbitrary surface profiles on the microscale. In this work, we introduce a new material system for structure formation by DLP that is based on photoreactive polymers for the local and light-induced C,H-insertion cross-linking (CHic). This approach allows a simple and versatile generation of microstructures with a broad spectrum of geometries and chemistries irrespective of the nature of the chosen substrates and thus allows direct writing of surface functionalization patterns with high spatial control. The CHicable prepolymer is first coated on a substrate to form a solvent-free (glassy) film, and then the DLP system patterns the light with arbitrary shape to induce local cross-linking of the prepolymer. Using this method, the desired structures with complex features with a lateral resolution of several microns and a topography of tens of nanometers could be fabricated within 30 s. Furthermore, the universal applicability of the CHic reaction enables the printing on a wide variety of substrates, which greatly broadens the using scenarios of this printing approach.

Manufacturing a Bone Marrow-On-A-Chip Using Maskless Photolithography.

The bone marrow (BM) is a complex microenvironment in which hematopoietic stem and progenitor cells (HSPCs) interact with multiple cell types that regulate their quiescence, growth, and differentiation. These cells constitute local niches where HSPCs are confined and subjected to specific set of physical and biochemical cues. Endothelial cells forming the walls of blood capillaries have been shown to establish a vascular niche, whereas osteoblasts lying along the bone matrix organize the endosteal niche with distinct and specific impact on HSPC fate. The observation of the interaction of HSPCs with niche cells, and the investigation of its impact on HSPCs behavior in vivo is hindered by the opacity of the bone matrix. Therefore, various experimental strategies have been devised to reconstitute in vitro the interaction of HSPCs with distinct sets of BM-derived cells. In this chapter, we present a method to manufacture a pseudo BM-on-a-chip with separated compartments mimicking the vascular and the endosteal niches. Such a configuration with connected but distant compartments allowed the investigation of the specific contribution of each niche to the regulation of HSPC behavior. We describe the microfabrication of the chip with a maskless photolithography method that allows the iterative improvement of the geometric design of the chip in order to optimize the adaptation of the multicellular architecture to the specific aim of the study. We also describe the loading and culture of the various cell types in each compartment.

Rapid Prototyping of Organ-on-a-Chip Devices Using Maskless Photolithography.

Organ-on-a-chip (OoC) and microfluidic devices are conventionally produced using microfabrication procedures that require cleanrooms, silicon wafers, and photomasks. The prototyping stage often requires multiple iterations of design steps. A simplified prototyping process could therefore offer major advantages. Here, we describe a rapid and cleanroom-free microfabrication method using maskless photolithography. The approach utilizes a commercial digital micromirror device (DMD)-based setup using 375 nm UV light for backside exposure of an epoxy-based negative photoresist (SU-8) on glass coverslips. We show that microstructures of various geometries and dimensions, microgrooves, and microchannels of different heights can be fabricated. New SU-8 molds and soft lithography-based polydimethylsiloxane (PDMS) chips can thus be produced within hours. We further show that backside UV exposure and grayscale photolithography allow structures of different heights or structures with height gradients to be developed using a single-step fabrication process. Using this approach: (1) digital photomasks can be designed, projected, and quickly adjusted if needed; and (2) SU-8 molds can be fabricated without cleanroom availability, which in turn (3) reduces microfabrication time and costs and (4) expedites prototyping of new OoC devices.

ZnO Nanowire-Anchored Microfluidic Device With Herringbone Structure Fabricated by Maskless Photolithography.

The integration of nanomaterials in microfluidic devices has emerged as a new research paradigm. Microfluidic devices composed of ZnO nanowires have been developed for the collection of urine extracellular vesicles (EVs) at high efficiency and in situ extraction of various microRNAs (miRNAs). The devices can be used for diagnosing various diseases, including kidney diseases and cancers. A major research need for developing micro total analysis systems is to enhance extraction efficiency. This article presents a novel fabrication method for a herringbone-patterned microfluidic device anchored with ZnO nanowire arrays. The substrates with herringbone patterns were created by maskless photolithography. The ZnO nanowire arrays were grown on the substrates by chemical bathing. The patterned design was to introduce turbulent flows as opposed to laminar flow in traditional devices to increase the mixing and contact of the urine sample with ZnO nanowires. The device showed reduced flow rates compared with conventional planar microfluidic channels and successfully extracted urine EV-encapsulated miRNAs.

Grayscale Nanopixel Printing at Sub-10-nanometer Vertical Resolution via Light-Controlled Nanocapillarity.

Nanotextures play increasingly important roles in nanotechnology. Recent studies revealed that their functionalities can be further enhanced by spatially modulating the height of their nanoscale pixels. Realizing the concept, however, is very challenging as it requires "grayscale" printing of the nanopixels in which their height is controlled within a few nanometers as a micrometric function of position. This work demonstrates such a high vertical and lateral resolution grayscale printing of polymeric nanopixels. We realize the height modulation by exploiting the discovery that the capillary rise of certain photopolymers can be optically controlled to stop at a predetermined height with sub-10-nm accuracy. Microscale spatial patterning of the control light directly extends the height modulation into a two-dimensionally patterned, grayscale nanopixel printing. Its utility is verified through readily reconfigurable, maskless printing of grayscale nanopixel arrays in dielectric and metallo-dielectric forms. This work also reveals the highly nonlinear and unstable nature of the polymeric nanocapillary effect, expanding its understanding and application scope.

Precise Micropatterning of a Porous Poly(ionic liquid) via Maskless Photolithography for High-Performance Nonenzymatic H2O2 Sensing.

Porous poly(ionic liquid)s (PILs) recently have been serving as a multifunctional, interdisciplinary materials platform in quite a few research areas, including separation, catalysis, actuator, sensor, and energy storage, just to name a few. In this context, the capability of photopatterning PIL microstructures in a porous state on a substrate is still missing but is a crucial step for their real industrial usage. Here, we developed a method for in situ rapid patterning of porous PIL microstructures via a maskless photolithography approach coupled with a simple electrostatic complexation treatment. This breakthrough enables design of miniaturized sensors. As exemplified in this work, upon loading Pt nanoparticles into porous PIL microstructures, the hybrid sensor showed outstanding performance, bearing both a high sensitivity and a wide detection range.