Transfer printing represents a set of techniques for deterministic assembly of micro-and nanomaterials into spatially organized, functional arrangements with two and three-dimensional layouts. Such processes provide versatile routes not only to test structures and vehicles for scientific studies but also to high-performance, heterogeneously integrated functional systems, including those in flexible electronics, three-dimensional and/or curvilinear optoelectronics, and bio-integrated sensing and therapeutic devices. This article summarizes recent advances in a variety of transfer printing techniques, ranging from the mechanics and materials aspects that govern their operation to engineering features of their use in systems with varying levels of complexity. A concluding section presents perspectives on opportunities for basic and applied research, and on emerging use of these methods in high throughput, industrial-scale manufacturing.

Transfer printing by kinetically switchable adhesion to an elastomeric stamp shows promise as a powerful micromanufacturing method to pickup microstructures and microdevices from the donor substrate and to print them to the receiving substrate. This can be viewed as the competing fracture of two interfaces. This paper examines the mechanics of competing fracture in a model transfer printing system composed of three laminates: an elastic substrate, an elastic thin film, and a viscoelastic member (stamp). As the system is peeled apart, either the interface between the substrate and thin film fails or the interface between the thin film and the stamp fails. The speed-dependent nature of the film/stamp interface leads to the prediction of a critical separation velocity above which separation occurs between the film and the substrate (i.e., pickup) and below which separation occurs between the film and the stamp (i.e., printing). Experiments verify this prediction using films of gold adhered to glass, and the theoretical treatment extends to consider the competing fracture as it applies to discrete micro-objects. Temperature plays an important role in kinetically controlled transfer printing with its influences, making it advantageous to pickup printable objects at the reduced temperatures and to print them at the elevated ones.

applications. Some notable examples of techniques motivated by topics attracting signifi cant attention in current research include nanoimprint lithography, [ 1 , 2 ] nanosphere lithography, [ 3 , 4 ] scanning probe lithography techniques, [ 5 , 6 ] and advanced forms of soft lithography, [7][8][9][10] including interference lithography with elastomeric contact masks. [11][12][13] Additionally, the realization of structures with triangular crosssections, such as cones and prisms, would enable applications in microfl uidic lab-ona-chip devices, [ 14 , 15 ] optical components, antirefl ective coatings, [ 16 , 17 ] self-cleaning surfaces with tuned contact angles, [18][19][20] surface enhanced Raman spectroscopy (SERS) sensing, [ 21 , 22 ] and probe-based patterning techniques. [ 23 , 24 ] A number of useful fabrication techniques have been developed to achieve this geometrical attribute, most commonly relying on etching to defi ne the patterns. The most commonly used method uses KOH-based anisotropic wet etching of Si(100) patterned with photoresist lines, to etch along the < 110 > direction and thus form an array of linear pits with isosceles triangle shaped cross-sections. [25][26][27][28] The feature pitch is dictated by the precision of the alignment of the photoresist features The use of a decal transfer lithography technique to fabricate elastomeric stamps with triangular cross-sections, specifi cally triangular prisms and cones, is described. These stamps are used in demonstrations for several prototypical optical applications, including the fabrication of multiheight 3D photoresist patterns with near zero-width features using near-fi eld phase shift lithography, fabrication of periodic porous polymer structures by maskless proximity fi eld nanopatterning, embossing thin-fi lm antirefl ection coatings for improved device performance, and effi cient fabrication of substrates for surface-enhanced Raman spectroscopic sensing. The applications illustrate the utility of the triangular poly(dimethylsiloxane) decals for a wide variety of optics-centric applications, particularly those that exploit the ability of the designed geometries and materials combinations to manipulate light-matter interactions in a predictable and controllable manner.

This paper describes soft lithography methods that expand current fabrication capabilities by enabling high‐throughput patterning on nonplanar substrates. These techniques exploit optically dense elastomeric mask elements embedded in a transparent poly(dimethylsiloxane) (PDMS) matrix by vacuum‐assisted microfluidic patterning, UV–ozone‐mediated irreversible sealing, and chemical etching. These protocols provide highly flexible photomasks exhibiting either positive‐ or negative‐image contrasts, which serve as amplitude masks for large‐area photolithographic patterning on a variety of curved (and planar) surfaces. When patterning on cylindrical surfaces, the developed masks do not experience significant pattern distortions. For substrates with 3D curvatures/geometries, however, the PDMS mask must undergo relatively large strains in order to make conformal contact. The new methods described in this report provide planar masks that can be patterned to compliantly compensate for both the displacements and distortions of features that result from stretching the mask to span the 3D geometry. To demonstrate this, a distortion‐corrected grid pattern mask was fabricated and used in conjunction with a homemade inflation device to pattern an electrode mesh on a glass hemisphere with predictable registration and distortion compensation. The showcased mask fabrication processes are compatible with a broad range of substrates, illustrating the potential for development of complex lithographic patterns for a variety of applications in the realm of curved electronics (i.e., synthetic retinal implants and curved LED arrays) and wide field‐of‐view optics.