All Publications


  • Tether-free photothermal deep-brain stimulation in freely behaving mice via wide-field illumination in the near-infrared-II window. Nature biomedical engineering Wu, X., Jiang, Y., Rommelfanger, N. J., Yang, F., Zhou, Q., Yin, R., Liu, J., Cai, S., Ren, W., Shin, A., Ong, K. S., Pu, K., Hong, G. 2022

    Abstract

    Neural circuitry is typically modulated via invasive brain implants and tethered optical fibres in restrained animals. Here we show that wide-field illumination in the second near-infrared spectral window (NIR-II) enables implant-and-tether-free deep-brain stimulation in freely behaving mice with stereotactically injected macromolecular photothermal transducers activating neurons ectopically expressing the temperature-sensitive transient receptor potential cation channel subfamily V member 1 (TRPV1). The macromolecular transducers, ~40 nm in size and consisting of a semiconducting polymer core and an amphiphilic polymer shell, have a photothermal conversion efficiency of 71% at 1,064 nm, the wavelength at which light attenuation by brain tissue is minimized (within the 400-1,800 nm spectral window). TRPV1-expressing neurons in the hippocampus, motor cortex and ventral tegmental area of mice can be activated with minimal thermal damage on wide-field NIR-II illumination from a light source placed at distances higher than 50 cm above the animal's head and at an incident power density of 10 mW mm-2. Deep-brain stimulation via wide-field NIR-II illumination may open up opportunities for social behavioural studies in small animals.

    View details for DOI 10.1038/s41551-022-00862-w

    View details for PubMedID 35314800

  • Microparticle transport along a planar electrode array using moving dielectrophoresis. Journal of applied physics Zaman, M. A., Padhy, P., Ren, W., Wu, M., Hesselink, L. 2021; 130 (3): 034902

    Abstract

    We present a device that can achieve controlled transport of colloidal microparticles using an array of micro-electrodes. By exciting the micro-electrodes in regular sequence with an AC voltage, a time-varying moving dielectrophoretic force-field is created. This force propels colloidal microparticles along the electrode array. Using this method, we demonstrate bidirectional transport of polystyrene micro-spheres. Electromagnetic simulation of the device is performed, and the dielectrophoretic force profile around the electrode array is mapped. We develop a Brownian dynamics model of the trajectory of a particle under the influence of the time-varying force-field. Numerical and experimental results showing controlled particle transport are presented. The numerical model is found to be in good agreement with experimental data. The developed numerical framework can be useful in designing and modeling lab-on-a-chip devices that employ external non-contact forces for micro-/nanoparticle manipulation.

    View details for DOI 10.1063/5.0049126

    View details for PubMedID 34334807