Making small liquid droplets move spontaneously on solid surfaces is a key challenge in lab-on-chip and heat exchanger technologies. Here, we report that a substrate curvature gradient can accelerate micro- and nanodroplets to high speeds on both hydrophilic and hydrophobic substrates. Experiments for microscale water droplets on tapered surfaces show a maximum speed of $0.42\mathrm{m}/\mathrm{s}$, 2 orders of magnitude higher than with a wettability gradient. We show that the total free energy and driving force exerted on a droplet are determined by the substrate curvature and substrate curvature gradient, respectively. Using molecular dynamics simulations, we predict nanoscale droplets moving spontaneously at over $100\mathrm{m}/\mathrm{s}$ on tapered surfaces.

In this work we report the development of the tri-functionalized mesoporous silica nanoparticles (MSNs) for use as theranostic compounds that orchestrate the trio of imaging, target and therapy in a single particle. The MSNs are functionalized in sequence with (1) contrast agents that enable traceable imaging of particle targeting, (2) drug payloads for therapeutic intervention and, (3) biomolecular ligands for highly-targeted particle delivery. Traceable imaging of nanoparticles was accomplished by directly incorporating a near-infrared (NIR) fluorescent contrast agent, ATTO647N, into the silica framework of MSNs, to exploit the relative transparency of most tissues at NIR wavelengths and maximize MSN surface area available for the subsequent conjugating drugs and targeting ligands. An oxygen-sensing, palladium-porphyrin based photosensitizer (Pd-porphyrin; PdTPP) was incorporated into the MSN's nanochannels, to enable photodynamic therapy (PDT). cRGDyK peptides, tiling the outermost surfaces of MSNs, were used for targeting the overexpressed α_vβ₃ integrins of cancer cells, and to ensure the internalization of the photosensitizer PdTPP. In vitro cell evaluation of the theranostic platform demonstrated not only excellent targeting specificity and minimal collateral damage, but highly potent therapeutic effect as well.

Functionalization of mesoporous silica nanoparticles (MSNs) with Pd-porphyrins for cancer cell photodynamic therapy is reported. The composite platform, MSN–PdTPP, expands the role of Pd-porphyrins from their routine use as phosphorescence probes for oxygen sensing/imaging (diagnostics) to that of novel nano-photosensitizers for cancer cell phototherapy (therapeutics). The utility of MSN–PdTPP in the phototherapeutic treatment of MDA-MB-231 breast cancer cells is also evaluated, suggesting it is a promising cancer theranostic platform.

In the past two decades, Micro Fluidic Systems (MFS) have emerged as a powerful tool for biosensing, particularly in enriching and purifying molecules and cells in biological samples. Compared with conventional sensing techniques, distinctive advantages of using MFS for biomedicine include ultra-high sensitivity, higher throughput, in-situ monitoring and lower cost. This review aims to summarize the recent advancements in two major types of micro fluidic systems, continuous and discrete MFS, as well as their biomedical applications. The state-of-the-art of active and passive mechanisms of fluid manipulation for mixing, separation, purification and concentration will also be elaborated. Future trends of using MFS in detection at molecular or cellular level, especially in stem cell therapy, tissue engineering and regenerative medicine, are also prospected.