Photonic professional gt

Metal-containing polymer structures were fabricated on a silicon chip (1 × 1 cm) using a commercially available TPL system (Photonic Professional GT, Nanoscribe GmbH). Metal-containing photoresist was drop cast on a glass slide (0.17 mm thick, 30 mm in diameter) and confined between the glass slide and a silicon chip using 100-μm thick, 2 × 10-mm ribbons of Kapton tape as spacers. Laser power and scan speeds were set at at 17.5–22.5 mW and 4–6 mm s⁻¹, respectively. After the printing process, the samples were developed in 2-methoxyethanol for 1 h, followed by immersion in PGMEA for 10 min and filtered IPA for 5 min. The samples were then processed in a critical point dryer (Autosamdri-931).

The phantom is fabricated using two-photon laser lithography, in which a focused laser beam is scanned within liquid resin. The resin within the laser’s focal volume is locally polymerized. Adjusting the scanning trajectory and the exposure time of the laser beam enables simultaneous control over the 3D printed geometry (accuracy at the order of 100 nm) and RI (accuracy at the order of $5\times {10}^{-4}$ , maximal $\mathrm{\Delta }$ RI = 0.03 within the structure) in three dimensions. We used Photonic Professional GT (Nanoscribe GmbH) equipped with a 1.3 NA 100 $\times$ microscope objective and piezo scanning stage. The phantom is fabricated in the IP-Dip resin (Nanoscribe GmbH) on top of a #1.5H coverslip (dip-in configuration⁵⁴ ). After fabrication the structure was developed in PGMEA (Propylene glycol monomethyl ether acetate; 12 min), followed by isopropyl alcohol (10 min) and then blow-dried. The full methodology for fabrication and validation of the features can be found in our previous work^{33 (link)}.
To conduct our TPM imaging experiments, the microphantom was immersed in Zeiss Immersol 518F oil (RI ${}_{632}$ nm = 1.5123), which provides similar RI contrast as in the case of cells immersed in culture medium. By using immersion oils with varying RI, it is possible to adjust the scattering properties of the microphantom post-fabrication.

GWL files were imported to a Nanoscribe Photonic Professional GT 3D printer (Nanoscribe, Eggenstein-Leopoldshafe, Germany) for 2PP exposure. The machine is equipped with a laser source emitting 100 fs pulses at 80 MHz, with a wavelength of 780 nm. A droplet of IPS photoresin (Nanoscribe, Eggenstein-Leopoldshafe, Germany) was placed on top of a 25 × 25 mm coverslip which had been previously coated with a thin indium tin oxide (ITO) layer to produce a refractive-index mismatch. The laser beam was then focused within the resin using a 25x microscope objective (numerical aperture [NA] = 0.8). The designed structures were written layer-by-layer with ultraprecise piezo actuators, moving the sample in the axial direction after exposing each layer. In the lateral direction, the laser beam was guided by galvanometric mirrors parallel to the substrate. After exposure, the development process was performed in propylene glycol monomethyl ether acetate (PGMEA) for 30 min followed by 2 min rinsing in isopropyl alcohol (IPA) and subsequent blow-drying with nitrogen.

Three-dimensional (3D) geometries were designed in Solidworks (Dassault Systèmes) or Solidedge (Siemens) and exported to STL format. After conversion to print-job instructions using DeScribe, devices were printed using the Nanoscribe Photonic Professional GT operating in dip-in mode with IP-S resin deposited onto an ITO coated glass slide or a silicon wafer. The printer was equipped with an 25x objective (all Nanoscribe GmbH). Devices were developed in ~20 ml of PGMEA for one to several days. Unexposed resin trapped in the shell and scaffold was cured after development through wide area UV lamp illumination (UV Curing Chamber, XYZprinting) for 30 min. A few hours prior to assembly they were transferred to isopropanol using a Pasteur pipette. Device assembly proceeded on a clean polydimethylsiloxane (PDMS) block (Supplementary Fig. 1). For this, devices solvated in isopropanol were transferred onto the PDMS with the Pasteur pipette and residual solvent around the 3D-printed microfluidic devices was wicked away and allowed to dry under atmosphere. After drying, a silicon adhesive Kapton® tape was used to fix the prints in place. Then HPLC tubing (Polymicro) was inserted into the fluid ports and glued in place using 5-min Epoxy (Devcom, Thorlabs).

The SVPC prototype is fabricated on a glass substrate with a negative tone photoresist (IP-Dip, Nanoscribe GmbH & Co. KG) using a commercially available 3D laser writing lithography system equipped with a femtosecond laser at λ = 780 nm (Photonic Professional GT, Nanoscribe GmbH & Co. KG). IP-Dip is a photoresist specially designed for Nanoscribe’s Dip-in Laser Lithography (DiLL) technology^{31 (link)}. This technique is capable, in principle, of ~ 300 nm lateral resolution and ~ 500 nm vertical resolution. The objective of the microscope is immersed directly into the liquid photoresist. IP-Dip acts as a photosensitive material and also as an immersion medium, providing ideal focusing and a high resolution (down to approximately 200 nm) because of its refractive index matching with the focusing optics^{32 (link)}. After the writing step, the sample is immersed in a bath of a developer (Propylene Glycol Monomethyl Ether Acetate, Sigma-Aldrich) and subsequently rinsed with isopropyl alcohol to remove the unpolymerized photoresist; it is then allowed to dry in air. The features of the prototype SVPC are inspected from a SEM image to assess and compare their structural forms to the designed structures.