Method and apparatus for single particle deposition

A method of depositing single particles via a droplet dispenser onto a target, wherein the droplet dispenser has a suspension reservoir and a nozzle having an ejection region and a sedimentation region upstream the ejection region, the droplet dispenser being capable of a dispensing operation wherein a particle suspension having the particles flows from the suspension reservoir through the nozzle towards a terminal opening of the nozzle at the ejection region and droplets of the particle suspension are dispensed through the terminal opening to the target, a nozzle camera is arranged for a particle detection including detecting particles in the particle suspension within the nozzle, a controller is arranged in electronic communication with the nozzle camera and with a testing unit including an image data storage for storing image data of an ejection region and a sedimentation region the method comprising:

• loading the particle suspension having the particles to the droplet dispenser having the suspension reservoir and the nozzle, wherein the droplet dispenser is capable of dispensing droplets having the particle suspension at a first droplet volume;
• detecting a presence of the particles in the particle suspension the nozzle via a nozzle camera;
• controlling the droplet dispenser via the controller based on a test procedure, which is capable of testing a single particle condition of the droplet dispenser via a testing unite to determine the single particle condition is fulfilled when an ejection region of the nozzle includes one single particle of the particles and eth sedimentation region adjacent to and upstream the ejection region is free the particles, wherein in the sedimentation region the particles are displaced to the ejection region by sedimentation between the step of detecting the presence of the particles and a step of controlling the droplet dispenser;
• and
• operating the droplet dispenser via the controller, wherein, in dependency on the single particle condition fulfilment, one of the droplets is dispensed from the droplet dispenser onto the target or at least one of the droplets is discarded from the droplet dispenser into a collection reservoir, wherein
• when the step of testing the single particle condition with the ejection region is not fulfilled, testing the single particle condition further includes
• reducing the ejection region according to an ejection region subsection and determining whether a current ejection region subsection includes one single particle and the sedimentation region adjacent to the current ejection region subsection is free of particles, and
• dispensing a fractional droplet having a fraction of the first droplet volume onto the target if the single particle condition is fulfilled with the current ejection region subsection.

A dispenser apparatus, being adapted for dispensing droplets including single particles onto a target, comprising:

• at least one droplet dispenser having a suspension reservoir and a nozzle configured to include a particle suspension, an ejection region and a sedimentation region upstream of the ejection region;
• a dispenser head arranged for carrying the at least one droplet dispenser;
• a nozzle camera arranged for detecting particles in the nozzle;
• a control device arranged electrical communication with the nozzle camera and for controlling the at least one droplet dispenser;
• and
• a testing unit coupled with the nozzle camera and with the control device and being adapted for (i) testing a single particle condition of the droplet dispenser, wherein during testing it is determined whether the ejection region of the nozzle includes one single particle and the sedimentation region adjacent to the ejection region is free of particles, wherein in the sedimentation region the particles are displaced to the ejection region by sedimentation during an operation delay interval between a step of detecting the presence of particles and a step of operating the droplet dispenser, and (ii) testing at least one of a zero particle condition of the droplet dispenser, wherein it is determined whether a predetermined volume equal to or larger than a 2-fold volume of the ejection region beginning at a tip of the nozzle of the droplet dispenser to the sedimentation region is free of particles to be dispensed, and a particle type condition, wherein it is determined whether detected particles have a predetermined particle type identified by at least one of size, shape, colour emission and absorption, wherein
• the control device is adapted for controlling the droplet dispenser based on the single particle condition, at least one of the zero particle condition and the particle type condition, a droplet is dispensed onto the target or discarded into a collection reservoir.