This talk will describe how innovations starting from a “chip level up” component innovation strategy drives system design, architecture choices and industrialization processes to fuel a technological paradigm shift in 3-D sensing. These innovations are enabling some of the biggest industries in the world, including transportation, aviation and smart cities. As an industry we are just in the early stages of unlocking the potential of lidar technology and will to unlock the next generation of vehicle safety and automated driving capabilities. This talk will discuss these innovations and discuss how lidar technology is transforming entire industries today and why there’s no sign of slowing down.

We show that optical coherence tomography (OCT) is a promising method for in-situ imaging during multi-photon laser printing. OCT measurements can provide access to properties and quality control of 3D printed microarchitectures. Our developed in-situ OCT system is fast and can be directly integrated into an existing multi-photon laser printer. Among demonstrated applications of the developed apparatus are photoresist-homogeneity inspection, evaluation of the polymer refractive index, thickness measurements of printed parts, etc. Obtained OCT reconstructions reveal optical imperfections in the printed specimens and can be compared with targeted 3D computer models.

Bioprinting allows for the formation of three-dimensional living tissues through the precise layer-by-layer printing of biomaterials such as living cells and cell-laden hydrogels. In this study, Laser-Induced Forward Transfer (LIFT) printing was used to rapidly and accurately deposit patterns of cancer cells in a non-contact manner using two different wavelengths, 532 and 355nm. Overall, we find that LIFT is able to safely print patterns of breast cancer cells with high viability and little to no heat or shear damage to the cells, as indicated by unperturbed growth and negligible gross DNA damage.

4D microprinting has become a promising strategy for the fabrication of dynamic microstructures opening new opportunities for the additive manufacturing of functional devices with high precision. During the last years, promising examples of defined 4D microstructures employing hydrogels, liquid crystals and composite materials have been shown using two-photon laser printing. Herein, we present our recent work on the field with emphasis on new responsive materials. In particular, shape memory polymers as well as dynamic covalent polymer networks have been demonstrated to be excellent candidates for the preparation of “living” 4D microstructures with potential applications in micro and nanorobotics or biomedicine.

Rapid multi-focus multi-photon laser printing suffers from insufficient photoresist sensitivity and limited focus quality. To overcome these problems and enable even higher printing rates, we present a novel approach for low-aberration and large field-of-view multi-focus printing with 7×7=49 foci at high focus scanning speeds. This is achieved by a combination of two 3D laser nanoprinted micro-optical elements: A low diffraction-order diffractive beam splitter to circumvent chromatic aberrations and an aspheric-lens array. The latter separates the diffracted beams to get a sufficient focus spacing. Together with highly sensitive photoresists we then allow for nanostructured sample dimensions inaccessible before.

Multi-material micro-nano-printing advances 3D additive fabrication towards true functional printing. Ultimately, full 3D digital fabrication searches full control over each individual atom. A polymer printing process that comes closest to this is 2-photon direct 3D laser writing. Multi-material printing has three challenges: materials, tools, and scalable processes. The material spectrum is continuously growing. Faster and more scalable processes will come from academic push and industrial pull. We contribute a novel material exchange process for 2-photon laser writers. Our in-situ material replacement exchanges printing material completely with fresh ones.

In recent years there have been notable efforts to make two-photon lithography more efficient and faster while avoiding trade-offs in resolution and print quality. The projection two-photon printing scheme achieves high-throughput while maintaining useful feature sizes. However, due to limitations of the temporal focusing process implemented, as well as photoresist kinetics, the resolution of this process does not yet reach that of single focus scanning two-photon lithography. This work explores the photoresist systems used for projection printing and the effect of additional optical beams for enhancing the printing capabilities of two-photon projection printing.

This presentation was prepared for SPIE LASE, 2023.

This presentation was prepared for SPIE LASE, 2023.

We review the progress in the field of 3D laser micro- and nanoprinting throughout the last ten years. In particular, this includes progress in regard to printing finer features, printing at higher print rates, making available more dissimilar materials, and in democratizing the technology, i.e., making it drastically less expensive. Moreover, we review new applications of the technology that have emerged.

This presentation was prepared for SPIE LASE, 2023.

This presentation was prepared for SPIE LASE, 2023.

Two-photon induced 3D laser lithography is a widely used technique in additive manufacturing of three-dimensional micro- and nanostructures. However, efficient two-photon absorption (2PA) comes at a cost: It requires femtosecond pulsed laser sources leading to large and expensive setups. Recently, we introduced two-step absorption (2SA) as a novel alternative excitation mechanism[1]. This allows for employing low-power continuous-wave light sources like inexpensive, compact semiconductor laser diodes for excitation. Here, we present a compact setup based on 2SA drastically reduced in cost and size showing the potential in the field of 3D laser lithography. [1] Vincent Hahn, Tobias Messer, N. Maximilian Bojanowski, Ernest Ronald Curticean, Irene Wacker, Rasmus R. Schröder, Eva Blasco, and Martin Wegener, Nat. Photon. 15, 932-938 (2021)

As the multi-photon lithography (MPL) field continues to advance, it is necessary to improve understanding of the underlying kinetics. A comprehensive model of 3D nanolithography is developed, where both the excited state kinetics of initiation by multi-step absorption and the kinetics of the resulting polymerization are simulated. The different model parameters are studied by fitting the model to experimental results and simulating the determination of effective nonlinearity values of the MPL process. Finally, the application of this model to projection MPL is investigated.

Fast laser curing is essential for highly accurate, high throughput additive manufacturing. High performance resins however exhibit relatively slow curing kinetics. In this talk we elaborate on the question if photopolymers relevant for technological applications can be processed with high-speed laser scanners. This is necessary to develop 3D printing systems that can compete in terms of accuracy and throughput with traditional manufacturing methods but outperform in terms of freedom of design and design agility. We compare exposure times spanning nine orders of magnitude and assess curing depths and double bond conversions obtained with different energy dosages and power densities.

Currently, printed electronics are manufactured by wet printing technologies such as inkjet and aerosol jet printers, which suffer from major drawbacks, including complex and expensive ink formulations, surfactants/contaminants, limited sources of inks, and the need for high-temperature post-processing. This talk will present a novel additive nanomanufacturing and dry printing technology for multimaterial printing of electronics, sensors, and energy devices. This technology allows in-situ and on-demand generation of various pure nanoparticles (metals, semiconductors, insulators, etc) in the printer head that are then directed toward the printer nozzle and laser-sintered in real-time to form desired patterns and structures layer-by-layer.

We introduce direct laser printing of functional electronics composed of conductive (Pt and Ag) and semiconducting (ZnO) materials with minimum feature sizes well below 1 µm. Our proof-of-principle experiments include diodes, transistors, memristors, and memristor-crossbar circuits forming a physically unclonable function. We emphasize that no sintering or other post-processing steps are necessary; the focused laser performs the lateral/vertical structuring as well as the material sintering. We expect that our laser-printing technique can be extended to many other semiconductor materials. Moreover, it can be combined with ink-jet printing. Therefore, laser printing provides a promising avenue for digitally printed electronics.

Aperiodic volume optics have been shown to be multiplexed optical devices that can produce different targeted output distributions from the same volume, only depending on the incoming illumination condition. These structures however have so far been produced inside of rigid glass substrates by introducing targeted microfractures through a focused laser. This makes following preparation steps necessary for any real-world applications, before even considering the illumination setup. We present a step towards the direct, additive manufacturing of multiplexed volume scattering devices by the creation of 3-dimensional structures using two-photon-polymerization, which is capable of creating complex optical microsystems, and their wave-optical simulation.

We present in situ monitoring of two-photon lithography with optical diffraction tomography (ODT) in an integrated home-built system. We show how two-photon lithographic system and intensity-based ODT can be organically integrated to provide reconstruction of 3D refractive index distribution of the printed structure at a diffraction-limited resolution. Due to ODT’s label-free nature, our method realizes in situ quality inspection of printed structure without specific sample preparation. In this way, our in situ observing solution can provide a timely feedback to the fabrication quality of two-photon lithography and potentially enables closed-loop optimizing and planning of printing parameters on-the-fly.

We present two mechanical metamaterials on the micrometer scale that change their mechanical behavior under irradiation with a blue LED. First, we show an auxetic metamaterial with a Poisson’s ratio that can be tuned on a large positive to negative values. Second, we demonstrate a chiral metamaterial with a tunable twist per strain that also varies from positive to negative values. For both examples, numerical finite-element calculations agree well with the measurements. Both metamaterials have been fabricated by two-photon microprinting of liquid-crystal elastomers in the presence of a tunable quasi-static electric field to align the local liquid-crystal director.

This presentation was prepared for SPIE LASE, 2023.

For additive manufacturing, scanning systems based on diode lasers offer unique advantages over conventionally used solid state lasers. Their fast modulation and high beam quality allow the production of precise polymer parts. However, the material portfolio which conventionally can be used on such stereolithography (SLA) systems is limited to resins which can be processed at room temperature. By controlled heating of a thinly coated material film (Hot Lithography), the available process window is significantly expanded. We present photopolymers with safe fire behavior of walls as thin as 0.45 mm. Using the precision of diode lasers without sacrificing fabrication speed, these materials are particularly suitable for the production of connectors for electronics industry.

Current 3D photonic device fabrication approaches can provide sub-wavelength feature sizes, but the ability to include multiple components at any desired location remains a challenge. Here we present an optical positioning and linking (OPAL) platform developed in our lab. It uses optical tweezers and biochemical linker molecules to create nanostructured photonic devices and 3D photonic metamaterials. We demonstrate the assembly of hundreds of microparticles into a 3D structure as well as discuss nanoscale processing speed and accuracy. We have applied OPAL to microtoroid optical resonator chemical gas sensors. Finally, we discuss novel nanophotonic design approaches tailored for compatibility with OPAL.

Here, we performed photoinitiator-free two-photon polymerization (TPP) to fabricate 3D cell micro-scaffolds. By using a visible femtosecond pulsed laser as excitation, TPP is induced in deep UV-absorbing moieties without the use of photo-initiators. We fabricated 3D micro-structures of biocompatible materials and glycidyl methacrylate protein without photoinitiators. By using Raman/Brillouin spectroscopy, we quantitatively investigated the molecular and mechanical properties of the 3D structures, which are important factors for cell functions and growth on scaffolds. We seeded cells on the 3D scaffolds and observed their attachment and proliferation without causing numerous cell deaths due to the absence of potentially cytotoxic photoinitiators.

Snapshot Image Mapping Spectrometer (IMS) allows to obtain 3D (x,y,lamda) datacubes instantaneously in a snapshot mode. The multifaceted mapping mirror is a critical component in the IMS for creating void spaces between image lines for spectral information. Here we present a completely new fabrication technique for mapping mirrors based on lithographic Two-Photon Polymerization (2PP). A grayscale 16-bit pixelized mapping mirror was designed in MATLAB, which allows to adopt 1-micron slicing distance and 0.2-micron hatching distance to keep low surface roughness while reducing printing time. The instability issue of the surface structure can be solved by adding two bases. Many other parameters (attenuation, develop time) used in 2PP printing were also optimized to provide the best surface quality. The new fabrication method decreases the facet shadowing (smaller height discrepancies), provides uniform image intensity, and enables easy reproducibility.