Fig. 1. Main optical principles, technologies, and applications of living-cell microlenses

Fig. 2. Four types of living-cell microlenses. (a) Electron microscope rendering image of Arachnoidiscusdiatom^[19]; (b) lensing effect of cyanobacteria^[9]; (c) light field distribution of diatom cells under circularly polarized light^[19]; (d) electron microscopy image of Escherichia coli; (e) experimental images of wild-type Escherichia coli and polysilicate-encapsulated Escherichia coli generating photonic nanojets^[16]; (f) numerical simulations showing that polysilicate-encapsulated Escherichia coli produce photonic nanojets^[16]; (g) simulation results of the focusing characteristics of three types of red-blood-cell (RBC) microlenses^[30]; (h) schematic of an RBC microlens for trapping fluorescent nanoparticles and enhancing their fluorescent signals^[15]; (i) numerical simulations of an nanoparticle trapping by RBC microlens^[15]; (j) optical morphology of an adipocyte, where lipid droplets labeled with red fluorescence, cytoskeleton with green fluorescence, and nucleus with blue fluorescence^[14]; (k) schematics of the intracellular microlenses (lipid droplet), and the yellow spherical structure depicts a lipid droplet exhibiting lens effects within the cell, enabling resolution-enhanced imaging of intracellular substructures^[14]; (l) schematics of the intracellular microlenses (chloroplast), and the green ellipsoidal structure depicts a chloroplast capable of modulating incident light^[40]

Fig. 3. Optical imaging applications of living-cell microlenses. (a) Imaging enhancement by spherical cell microlenses of different types^[46]; (b) imaging enhancement by the RBC microlenses of divergent shapes^[15]

Fig. 4. Optical detection applications of living-cell microlenses. (a) Excitation and detection of local fluorescence from a leukemia cell in human blood by manipulating the bionanospear to scan the cell, and flexibility testing by pushing the bionanospear against the cell membrane of a leukemia cell^[48]; (b) lensing effect of various live cells^[50]

Fig. 5. Optical fabrication applications of living-cell microlenses. (a) Schematic view of bio-photolithography by RBC biolenses, reconstructed amplitude and phase of discocytes and the corresponding imprints^[53]; (b) lithography-based measurement of near-field optical effects of cyanobacteria^[9]

Fig. 6. Optical transmission applications of living-cell microlenses. (a) Nonlinear self-trapping of light through cyanobacteria in seawater^[59]; (b) RBC waveguides in blood solutions with different pH values^[63]