We describe the fluidFM, an atomic force microscope (AFM) based on hollow cantilevers for local liquid dispensing and stimulation of single living cells under physiological conditions. A nanofluidic channel in the cantilever allows soluble molecules to be dispensed through a submicrometer aperture in the AFM tip. The sensitive AFM force feedback allows controlled approach of the tip to a sample for extremely local modification of surfaces in liquid environments. It also allows reliable discrimination between gentle contact with a cell membrane or its perforation. Using these two procedures, dyes have been introduced into individual living cells and even selected subcellular structures of these cells. The universality and versatility of the fluidFM will stimulate original experiments at the submicrometer scale not only in biology but also in physics, chemistry, and material science.

FluidFM: Combining Atomic Force Microscopy and Nanofluidics in a Universal Liquid Delivery System for Single Cell Applications and Beyond

Biological cell injection is laborious work that requires lengthy training and suffers from a low success rate. In this paper, a robotic cell-injection system for automatic injection of batch-suspended cells is proposed. To facilitate the process, these suspended cells are held and fixed to a cell array by a specially designed cell-holding device, and injected one by one through an ldquoout-of-planerdquo cell-injection process. A micropipette equipped with a polyvinylidene fluoride microforce sensor to measure real-time injection force is integrated in the proposed system. Through calibration, an empirical relationship between the cell-injection force and the desired injector pipette trajectory is obtained in advance. Then, after decoupling the out-of-plane cell injection into a position control in the X - Y horizontal plane and an impedance control in the Z -axis, a position and force control algorithm is developed to control the injection pipette. The depth motion of the injector pipette, which cannot be observed by microscope, is indirectly controlled via the impedance control, and the desired force is determined from the online X - Y position control and cell calibration results. Finally, experimental results demonstrate the effectiveness of the proposed approach.

Robotic Cell Injection System With Position and Force Control: Toward Automatic Batch Biomanipulation

Robotic cell microinjection is a technique that utilizes automation technology to insert substances into a single living cell with a fine needle. Compared with manual microinjection, the main benefits of the robotic cell injection are quality, productivity and repeatability. In this paper we aim to control the penetration force during robotic cell injection to quantify the influence of the penetration force on cells. A force-control-based cell injection approach that is capable of regulating the penetration force in a desired force trajectory is developed. The proposed force control framework includes two control loops. The inner loop is an impedance control used to specify the interaction between the needle and the cell. The outer loop is a force tracking non-linear controller using a feedback linearization technique. The cell model is identified online with a least-squares parameter estimator. With the proposed force control approach, the penetration force can be regulated explicitly to follow the desired force trajectory during the cell injection process. Experiments performed on fish embryos verify the effectiveness of the proposed approach.

A Force Control Approach to a Robot-assisted Cell Microinjection System

In this paper, we report the development of a prototype micromanipulation system for automatic batch microinjection of zebrafish embryos. Such automatic batch processing is made possible by (i) the development of a machine vision algorithm to identify the number of embryos in a batch and to locate the centerline of each embryo, (ii) the integration of a piezoresistive micro-force sensor with a micropipette to measure the penetration force of the embryo in real time and (iii) the synthesis of a position control with dynamic force feedback by exploiting the characteristics of the force profile associated with the microinjection process. The effectiveness of this prototype micromanipulation system has been demonstrated in an experiment. The experimental results demonstrate that the technique of position control with dynamic penetration-force feedback is practicable for automatic batch microinjection applications.

https://iopscience.iop.org/article/10.1088/0960-1317/17/2/018/pdf

A micromanipulation system with dynamic force-feedback for automatic batch microinjection

This paper reviews the technologies that have been invented in the last few years on high-throughput phenotyping, imaging, screening, and related techniques using microfluidics. The review focuses on the technical challenges and how microfluidics can help to solve these existing problems, specifically discussing the applications of microfluidics to multicellular model organisms. The challenges facing this field include handling multicellular organisms in an efficient manner, controlling the microenvironment and precise manipulation of the local conditions to allow the phenotyping, screening, and imaging of the small animals. Not only does microfluidics have the proper length scale for manipulating these biological entities, but automation has also been demonstrated with these systems, and more importantly the ability to deliver stimuli or alter biophysical/biochemical conditions to the biological entities with good spatial and temporal controls. In addition, integration with and interfacing to other hardware/software allows quantitative approaches. We include several successful examples of microfluidics solving these high-throughput problems. The paper also highlights other applications that can be developed in the future.

Microfluidics-enabled phenotyping, imaging, and screening of multicellular organisms

In this paper, we report the development of an explicit force-feedback control system for micro-assembly, focusing on the key issues of force transmission and control. The force-feedback system is incorporated with a compound flexure stage, which is driven by a voice-coil actuator and designed to provide frictionless translation motion along one axis. A force sensor measures the interaction force between the micromanipulator and its environment, while an explicit force controller controls the interaction force to follow a desired force trajectory. The effectiveness of this prototype force-control system has been demonstrated in an experimental application, where parts (with dimensions in microns) were picked up and assembled under explicit force-feedback control.

https://iopscience.iop.org/article/10.1088/0960-1317/16/9/015/pdf

A force-feedback control system for micro-assembly

Models of maximum stress and strain of zebrafish embryos under indentation.

In this paper we formulate an optimization problem in the design of a speed trajectory for the motion of the micropipette during automated microinjection of zebrafish embryos. The objective of this optimization problem is to minimize the deformation sustained by the zebrafish embryo. We subsequently propose a solution to this optimization problem by first constructing a viscoelastic model of the zebrafish embryo, and then synthesizing an optimal speed trajectory based on a class of polynomials. Furthermore, we present results of numerical simulation and experiments that demonstrate the effectiveness of the proposed solution. The statistically meaningful experimental data (generated using a large sample of zebrafish embryos) provide direct evidence on the advantage of such speed optimization in microinjection.

Speed optimization in automated microinjection of zebrafish embryos

This paper studies the feasibility of using force measurement to detect wire vibration for the evaluation of wire bond integrity. In this system, a tapping probe sends a single pulse or multiple pulses of controlled motion to the substrate adjacent to a bond end. This mechanical shock induces vibration propagation to the wire along and through the neighbouring materials. Another probe of a micro force sensor is put in touch with the wire to pick up the wire vibration, which in turn, correlates to the bonding status of the joined materials. By interpreting the vibration signals in time, frequency, and phase domains, bond integrity, including fully bonded, partially bonded, and touching yet not-bonded, has been determined. The results show that the proposed approach is promising for finer and denser wire bond evaluation non-destructively, accurately, and at low cost.

Joohoo Nam

Papers

A micromanipulation system with dynamic force-feedback for automatic batch microinjection

A force-feedback control system for micro-assembly

Models of maximum stress and strain of zebrafish embryos under indentation.

Speed optimization in automated microinjection of zebrafish embryos

Evaluation of wire bond integrity through force detected wire vibration analysis