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.


Shaping active pressure with light

If a colloidal sphere is placed at the interface between fast and slow bacteria, individual cells will push more on the fast side, but there will be more in the slow region. So in which direction will it move?
video: Shaping active pressure with light

Light programmable micro-robots

Microscopic biohybrid robots can be remotely controlled by unbalancing light projected on two bacterial motors. These microbots can be independently programmed to navigate a route and maybe one day deliver cells in microfluidic chips.
video: Microscopic biohybrid robots remotely controlled by light

Herding bacteria with light

Light-guided bacteria can be confined to regions of high density and motility using a computer-controlled structured illumination in which tiny 'sheepdogs' of light prevent the bacteria from escaping.
video: Rounding up bacteria using computer-controlled 'sheepdogs' of light

Virtual micro-Reality

By using Virtual Reality to combine holographic microscopy with optical tweezers, you can "shrink" your body to microscopic size and use your hands to play with colloids, build 3D microstructures, and catch swimming bacteria on the fly.
video: Virtual Micro Reality
press: Viaggiare nel corpo umano è (quasi) possibile (Repubblica).

Too much confinement makes bacteria swim faster

Swimming in conditions of increasing confinement usually results in lower speeds. When E.coli bacteria swim through narrow channels, axial swimming becomes hydrodynamically stable allowing bacteria to move faster than when outside.
video: Too much confinement makes bacteria swim faster

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

Bacteria explore disordered environments with a mean residence time that is invariant on the number of random obstacles and only depends on the surface to perimeter ratio of the region.
video: Bacteria swimming in artificial random environments
press: Obstacle course (Nature Physics)

A light sprinkler

Light guiding 3D microstructures rotate when light flows through them like water in a garden sprinkler.
video: An optical reaction microturbine
press: Light sprinkler (Nature Photonics)

Using light as a brush for bacterial portraits

E.coli bacteria, 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 holographic microscopy and optical tweezers, we can analyze hundreds of 3D collisions between swimming bacteria and solid walls decoupling steric and hydrodynamic effects in wall entrapment.
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 asymmetric barriers with unbalanced jump rates.
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.



Introduzione alla fisica dei sistemi biologici (Genetica ed evoluzione) - Laurea Triennale in Fisica
Registration A.A. 2023/2024
Biophysics - Laurea Magistrale in Fisica
Registration A.A. 2023/2024
Termodinamica e Laboratorio - Laurea Triennale in Fisica
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

Understanding DNA Photo 51

An interactive X-ray diffraction simulator that teaches how to read the famous photo 51, the DNA "image" that was crucial in the discovery of the double-helix structure.
Go to app page