Roberto Di Leonardo
Full Professor
Dipartimento di Fisica
Sapienza Università di Roma
Piazzale Aldo Moro 5
00185 Roma, Italy
(+39) 06 4991 3518 (office)
(+39) 06 4969 3294 (lab)


From the Brownian movements of inanimate matter to the swimming motility of bacteria, the world at the micron scale is extremely dynamic. We are interested in the origins, the consequences and the applications of these motions. To study that, we build digital microscopes that integrate optical and computer hardware and where light can be used for imaging, manipulation and fabrication of microsystems in 3D.


Too much confinement makes bacteria swim faster

Swimming in conditions of increasing confinement usually results in lower speeds. In E.coli just before confinement becomes extreme, and the width of a microcapillary falls below 2.5 the cell thickness, axial swimming becomes hydrodynamically stable and makes bacteria move faster through narrow spaces.
video: Too much confinement makes bacteria swim faster

How fast can bacteria escape from a confined space full of obstacles?

Bacteria swim through microstructures containing random obstacles with a mean residence time that is invariant with respect to the amount of internal disorder and depends on shape only through surface to perimeter ratio.
video: Bacteria swimming in artificial random environments
press: Obstacle course (Nature Physics)

A light sprinkler

Light guiding 3D microstructures can reroute an incoming flow of optical energy to generate a strong, uniform and controllable torque.
video: An optical reaction microturbine
press: Light sprinkler (Nature Photonics)

Using light as a brush for bacterial portraits

E.coli bacterial cells, genetically engineered to have a light controllable swimming speed, can be remotely controlled with light to form an accurate millimetric replica of Leonardo’s Mona Lisa.
video: Light controlled bacteria draw morphing micro-portraits
press: The world's smallest masterpieces (Daily Mail)
Ritratto con i batteri (Repubblica)

Biohybrid 3D printed micro-machines driven by light

Genetically modified bacteria, expressing the protein proteorhodhopsin, can be used as tiny propellers in micromachines that are invisible to the human eye and whose speed can be reliably and continuously tuned by shining green light of controlled intensity.
video: Swimming bacteria pushing 3D printed micromotors
press: Micromotors are powered by bacteria, controlled by light (

Watching wall entrapment of bacteria in 3D

Using a combination of our 3-axis holographic microscopy and optical tweezers, we could visualize in 3D the wall entrapment dynamics of swimming cells that are sequentially released from a controlled distance and angle.
video: 3D movie of bacteria colliding with a flat wall.
press: Bacteria bounce along walls like flies bounce along a window


A rotating micromotor can self-assemble starting from randomly distributed Janus particles and microfabricated passive ratchets.
video: Self-assembly of a rotating structure.
press: Microgears rotate when pushed by tiny motors (

Light-to-work conversion at the micron-scale

Light-absorbing microgears, sitting on a liquid-air interface, can efficiently convert light into rotational motion through a thermo-capillary effect.

video: Spinning gears at different light power levels
press: Tiny gears increase light-to-work conversion efficiency by five orders of magnitude (
Powering Gears with Light (APS Physics)

A stationary probability density for active matter

We derive the stationary probability distribution for a non-equilibrium system composed by an arbitrary number of degrees of freedom that are subject to Gaussian colored noise and a conservative force field.
press: CondMat Journal Club

Bacteria can be trapped by convex walls (if curvature is low enough)

E. coli cells can be stabily trapped by the lateral convex surface of micro pillars provided the pillar radius is larger than a critical value.

Bacteria deliver colloidal cargoes on tartget sites

Bacteria can autonomously transport colloidal cargoes onto target sites that are surrounded by micro-fabricated asymmetric landscapes in 3D.
press: Le Scienze

Optical trapping at Gigapascal pressures

The full power of holographic optical tweezers can be made available inside diamond anvil cells for high pressure rheological and mechanical studies in physics and biology.
press: APS Physics

Seeing and touching through an optical fiber

A single multimode optical fiber can be used as a submillimiter probe for interactive micromanipulation and fluorescence microscopy.
press: LaserFocusWorld

Light driven micromotors spin in sync

Optically trapped micro-rotors rotate in phase when close enough to interact hydrodynamically.
video: Movie showing two "lightmills" spinning in sync.



A.A. 2020/2021
Termodinamica e Laboratorio - Laurea Triennale in Fisica
A.A. 2019/2020
Termodinamica e Laboratorio - Laurea Triennale in Fisica
Biophysics - Laurea Magistrale in Fisica
A.A. 2018/2019
Termodinamica e Laboratorio - Laurea Triennale in Fisica
Data analysis - Laurea Magistrale in Genetica e Biologia Molecolare
A.A. 2017/2018
Termodinamica e Laboratorio - Laurea Triennale in Fisica
Data analysis - Laurea Magistrale in Genetica e Biologia Molecolare
A.A. 2016/2017
Costruzione di modelli fisici per la biologia - Scuola Superiore di Studi Avanzati Sapienza
Data analysis - Laurea Magistrale in Genetica e Biologia Molecolare

Web apps

Trapping force in optical tweezers

A ray optics interactive simulation that illustrates how transfer of optical momentum due to reflection and refraction can lead to the stable 3D trapping of a dielectric sphere.
Go to app page

Non equilibrium stationary states of active particles

A stochastic dynamics simulation that illustrates some "odd" off-equilibrium properties of active particles such as wall accumulation and ratcheting.
Go to app page