On-demand, remote and lossless manipulation of biofluid droplets

Abstract

The recent global outbreaks of epidemics and pandemics have shown us that we are severely under-prepared to cope with infectious agents. Exposure to infectious agents present in biofluids (e.g., blood, saliva, urine etc.) poses a severe risk to clinical laboratory personnel and healthcare workers, resulting in hundreds of millions of hospital-acquired and laboratory-acquired infections annually. Novel technologies that can minimize human exposure through remote and automated handling of infectious biofluids will mitigate such risk. In this work, we present biofluid manipulators, which allow on-demand, remote and lossless manipulation of virtually any liquid droplet. Our manipulators are designed by integrating thermo-responsive soft actuators with superomniphobic surfaces. Utilizing our manipulators, we demonstrate on-demand, remote and lossless manipulation of biofluid droplets. We envision that our biofluid manipulators will not only reduce manual operations and minimize exposure to infectious agents, but also pave the way for developing inexpensive, simple and portable robotic systems, which can allow point-of-care operations, particularly in developing nations.

Figure 1.. Biofluidic manipulator.

(a) Schematic depicting the twisted-and-coiled actuator (TCA) fabricated with conductive nylon sewing thread. When a voltage is applied, the TCA extends in length. (b) Schematic illustrating the fabrication of soft manipulator by embedding a single heterochiral TCA between softer and stiffer elastomer layers. (c) Schematic depicting the soft manipulator after embedding a single TCA between the softer and stiffer elastomer layers. (d) Schematic depicts the bending process of our soft manipulator. (e) and (f) Pictures showing the bending of the soft manipulator when a voltage is applied. (g) Blocking force generated by the soft manipulator at different bending curvatures. (h) and (i) Apparent contact angles and roll off angles, respectively, of liquid droplets with different surface tensions on our superomniphobic surfaces. Roll off angles were measured with 20 μl droplets. The inset shows the morphology of our superomniphobic surfaces.

Figure 2.. Manipulators for in-plane droplet manipulations.

(a)-(b) and (c)-(d) On-demand, remote and lossless, in-plane simultaneous manipulation of water droplets (dyed blue and red) and n-hexadecane droplets (colorless and dyed red), respectively, with our biofluid manipulator. Upon actuation, the two droplets are transported simultaneously along the surface and mixed with each other. (e) Schematic depicting the design of three manipulators for in-plane sequential manipulation of droplets. Each manipulator can be actuated independently. (f)-(i) On-demand, remote and loss-less, in-plane sequential manipulation of water droplets. Upon actuation, each droplet is sequentially transported to the trapping site (i.e., triangular-shaped domain).

Figure 3.. Droplet gripper.

(a)-(c) Droplet gripper consisting of two manipulators. When the voltage was applied, distance between the manipulators decreased until they contacted each other. When the voltage was turned off, the gripper recovered its original shape. Scale bar represents 5 mm. (d) The droplet gripper holding a 3.6 g gallium-indium liquid metal droplet. Scale bar represents 5 mm. (e)-(g) and (h)-(j) On demand, remote and lossless, pick-and-place operations (i.e., out-of-plane manipulation) of water droplets (dyed blue and yellow) and n-hexadecane droplets (colorless and dyed red), respectively.

Figure 4.. Biofluid droplet manipulation.

(a)-(c), (d)-(f) and (g)-(i) On-demand, remote and lossless in-plane simultaneous mixing of BSA, milk and virus replicon particle-laden droplets, respectively, with Bradford reagent (right; reddish brown) to demonstrate protein detection. (j)-(l), (m)-(o) and (p)-(r) On-demand, remote and lossless in-plane simultaneous mixing of whole blood, PRP and fibrinogen droplets, respectively, with thrombin (right) to demonstrate clotting. Scale bar represents 10 mm.