Using　light　to　dynamically　and　stably　redirect　the　flow　of　another　beam　of　light　is　a　long-term　goal　for　photonic-integrated　circuits.　However,　it　is　challenging　to　realize　a　practically　all-optical　switching　device　in　silicon　owing　to　its　weak　optical　nonlinearity.　Major　published　work　on　all-optical　switches　were　using　single-photon　absorption　and　two-photon　absorption,　which　requires　ultrahigh　switching　energy.　This　paper　presents　a　nano-silicon-photonic　all-optical　switch　driven　by　an　optical　gradient　force,　in　which　a　fast　switching　speed　with　low　power　consumption　is　obtained.　Each　switching　element　is　composed　of　a　waveguide　crossing　connection　and　a　micro-ring　resonator.　The　ring　resonator　is　side-coupled　to　a　double-etched　waveguide　crossing,　while　the　micro-ring　resonator　is　partially　released　from　the　substrate　and　becomes　free-standing.　When　the　＂drop＂　port　is　in　＂OFF＂　state,　the　wavelength　of　the　signal　light　from　the　＂input＂　port　does　not　satisfy　the　resonant　condition　in　the　micro-ring.　Therefore,　light　is　mainly　transmitted　to　the　＂thru＂　port　without　control　light.　When　a　control　light　is　loaded　to　the　＂add＂　port,　of　which　the　wavelength　satisfies　the　resonance　condition　in　the　micro-ring,　a　strong　optical　gradient　force　is　generated　by　the　induced　evanescent　optical　field.　The　freestanding　arc　of　the　ring　is　then　bent　down　to　the　substrate,　leading　to　a　cavity　resonance　wavelength　shift.　As　a　result,　the　signal　light　is　diverted　to　the　＂drop＂　port　and　the　corresponding　transmission　state　is　switched　to　the　＂ON＂　state.　The　optical　switch　is　fabricated　by　nano-photonic　fabrication　processes　using　standard　silicon-on-insulator　(SOI)　wafer.　The　waveguide　structures　have　a　width　of　450　nm　and　a　height　of　220　nm　for　a　single　mode　transmission;　the　outer　radius　of　the　ring　in　the　switching　element　is　15　mu　m;　the　coupling　gap　between　the　ring　and　the　nano-waveguide　is　200　nm;　the　system　is　fabricated　through　two-step　lithography　and　plasma　dry　etching　processes　while　the　free-standing　arc　is　released　by　undercutting　the　buried　oxide　layer.　A　switching　time　of　180　ns(rise)　and　170　ns　(fall)　is　experimentally　demonstrated,　which　is　much　faster　than　that　of　conventional　optical　switches.　The　present　optical　switch　can　reach　a　high　extinction　ratio　(10.67　dB)　and　a　low　crosstalk　(-11.01　dB).　In　addition,　the　proposed　switch　has　the　advantages　of　compact　size　and　low　power　consumption.　Potential　applications　of　this　optical　switch　include　photonic　integrated　circuits,　signal　processing,　and　high　speed　optical　communication　networks.