AbstractWe propose to develop 3D printing technology of glass micro-objective and micro optics for ultrathin endoscopeto address the increasing demand in developing compact endoscopes in cancer imaging. The primary challengein developing micro-objective is the fabrication traditional fabrication methods dont have sufficient capabilitiesin fabricating micro optics. GRIN lens is the only commercially available micro-objective but it has a number oflimitations such as narrow working spectrum and very short working distance. 3D printing process has beendeveloped recently to print polymer micro-objective with two-photon polymerization (TPP) process. Howeverthere are some inherent limitations in printed polymer optics including short lifetime due to the yellowish lowtransmission in UV and NIR spectrum and limitations in hardness thermal resistance and chemical resistance.Glass optics is preferred for clinical application because of its excellent optical chemical and thermal properties.To meet the increasing needs of high-precision glass micro-optics for endoscope and address the majorlimitations of current 3D printing optics we have developed a solvent-free pre-condensed liquid silica resin (LSR)and two-photon 3D printing process for glass optics. 3D printing of glass micro-optics with isotropic shrinkagemicrometer resolution low deviation peak-to-valley value (<100 nm) and low surface roughness (< 6 nm) hasbeen achieved. The solvent-free UV curable LSR with a majority of the already formed covalent bonds(Si-O-Si) is novel that it significantly reduces the material shrinkage increases the printing speed and simplifiesthe process to obtain inorganic silica. The printed glass micro optics has better imaging performance withhigher resolution wider working spectrum better transmission from UV to NIR and longer lifetime. The 3Dprinting process for micro glass objective is novel in that it can fabricate more complex optical systems andis particularly suitable for rapid prototyping at low-cost.The goal of this project is to develop 3D printed glass micro-objective and micro optics for ultra-compactendoscope. We will first optimize pre-condensed LSR (Aim 1) and then print micro-objectives and evaluate theperformance (Aim 2).This project is significant in that it will establish a new 3D printing technology for fabricating the much-neededglass micro-objective and micro-optics for endoscope in cancer imaging. The rapid prototyping capability at lowcost will accelerate the rapid transition of the advanced imaging technologies from the lab to clinical applications.